Fast lenses, and High ISO

Started 3 months ago | Discussions
mosswings
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Re: Understanding ISO
In reply to bobn2, 3 months ago

bobn2 wrote:

mosswings wrote:

Chikoo wrote:

Austinian wrote:

Great Bustard wrote:

The most important factors about the sensor that manufacturers do not tell us are:

  • QE (Quantum Efficiency -- the proportion of light falling on the sensor that is recorded)
  • Read Noise (the additional electronic noise added by the sensor and supporting hardware)
  • CFA (Color Filter Array)
  • Microlens Efficiency

Which of these are likely to see significant improvements in the fairly near term (next few years)?

If by significant you mean something that might garner an extra stop or more of performance, it's hard to say. There has been recent work by Panasonic on a different type of CFA that eliminates the losses inherent in current implementations and that theoretically could yield a stop, perhaps more, in sensitivity:

http://www.imaging-resource.com/news/2013/02/05/bye-bye-bayer-panasonic-claims-new-sensor-tech-ends-color-filter-light-loss

It's been over a year since this announcement, but no updates. One of the problems of this technique may lie in tailoring the color splitting response to produce acceptable color rendition. Given all the complaints about current CFAs, it will need to be no worse.

BSI (backside illumination) is the current go-to for increasing sensor QE. Sony calls it EXMOR-R and it is found on no larger than 1" sensors as it involves thinning the sensor wafer down to a few 10s of microns in order to expose the pixel wells from the backside. Doing this for a larger format sensor is still impractical as it dramatically weakens the chip.

Sony's trying to curve their sensor to eliminate corner vignetting and the need for tricky microlens tailoring. It also has the side effect of improving sensor response by straining the sensor lattice, but again it's an expensive technique.

Read noise can be attacked in several ways, but another way of dealing with the problem may be in redefining the entire imaging process. This is what Eric Fossum has been working on with his Quanta Imaging Sensor. It basic trades the charge-integrating approach of today for a photon-counting approach using a combination of extremely dense binary-response pixel arrays, high frame capture rates, and heavy postprocessing - 100+MP arrays, 1000 frames/sec capture rates using fairly conventional CMOS technology. In doing so one can trade off resolution for DR, tailor tonal response directly, possibly directly compensate for camera motion, etc. etc.. The downside is that it requires pixel read noise to be about 4 stops better, but since it's not trying to do a linear amplification, more options for doing so are open to the designer. Research chips are in development now, but we have a long road to go.

Use a transparent wafer for BSI?

For electronic and manufacturing reasons you have to start with silicon, which isn't. But beyond that, you have to clear away all the wiring and other structures to gain QE, which is what BSI does - it flips the chip over where there isn't any wiring. The flipped wafer can then be cemented to a carrier substrate - a ceramic carrier, or something like that - and the back of the wafer ground down to the required thickness. A lot of today's ICs include what amounts to a pass with a wet sander.

There are two processes for BSI. One grows silicon epitaxy over a transparent (sapphire) wafer and then builds the circuits in the silicon. The other is the process you describe. I suspect that wafer thinning by grinding, as you describe, is going to cause too much silicon damage for it to be used, I suspect it is done by etching, dry or wet.

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Bob

Yes, exactly. Sapphire is not exactly cheap, and the issue of defect generation caused by surface imperfections and lattice mismatch are big issues...but the bigger the sensor chip, the more you have to start by an eptaxial layer growth step. Many ICs are grown epitaxially on an oxidized bulk silicon wafer for isolation and performance gains, but management of the defect generation mechanisms inherent in doing so has always been an issue.  Unfortunately, the need to pass visible light precludes this well-established carrier technology.

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John Sheehy
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Re: Understanding ISO
In reply to Great Bustard, 3 months ago

Great Bustard wrote:

  • Photon Noise (noise from the light itself)
  • Read Noise (additional electronic noise from the sensor and supporting hardware)

So far as photon noise goes, modern sensors have a QE of right around 50%. What this means is that half of the light that makes it through the CFA (Color Filter Array) onto the pixel is recorded. Thus, for a Bayer CFA, there's only a stop more to go to 100% efficiency.

... in the green channel. The blue and red channels can improve even further. For future sensor geometries, red capture could conceivably increase by

In other words, what we want is lower read noise, not "higher ISO". The thing is, though, a read noise of 2-3 electrons per pixel is already pretty low (considering that the pixels on FF DSLRs, for example, are able to produce signals of around 100,000 electrons), so why are high ISO photos noisy? The answer is simple: they get very little light, and less light means more noise.

2-3 electrons is not a big issue at base ISO, with big pixels, but for small pixels and and high ISOs it is tremendous read noise. And of course, real world read noise does not look like gaussian noise created by a computer; it is highly correlated, visually, even if not significantly so, as a statistic.

In other words, it's not like sensors can keep on getting more and more efficient and low light photography will get less and less noisy. For sure, the read noise represents a kind of floor beyond which the noise in the photo quickly diminishes. But even with zero read noise, we are limited by the light itself.

That limit is much farther away, and is only limited in regard to how much we want to magnify the capture in display. Pure photon captures can work very well with very, very tiny signals if you do not need to display them large. They have no contrast issues in near-blacks, and no linearity problems down there, either.

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John Sheehy
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Re: Fast lenses, and High ISO
In reply to Chikoo, 3 months ago

Chikoo wrote:

Fast lenses, as they are called allow for more light to hit the sensor and in turn allow for fast(er) shutter speeds. The F number provides a relative measure of how much this ability is.

In this age of ever increasing ISO, are fast lenses needed anymore?

High ISO has always been available to the RAW shooter. If your camera maxed out at ISO 1600, and you set your camera to a certain shutter speed and f-stop, and needed to push the capture 6 stops in conversion, then you are really doing an ISO 1600 * 2^6 = ISO 102,400. Did that all the time with my first DSLRs when the flash did not fire or the batteries died.

THe difference between older and newer cameras is the results are now more acceptable, at higher ISOs.

The only ability I see the fast lenses provide was actually a disadvantage that happened to become a feature, and that is shallow DoF, allowing for separation of subject from the background.

I've been in Manhattan at night shooting on poorly-lit side streets and I've had -3 EV on my meter in manual mode at ISO 25,600, at f/1.4 and 1/40.

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Albert Silver
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Re: "fast" is relative
In reply to bobn2, 3 months ago

bobn2 wrote:

Albert Silver wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

That was my point, though I think Bob missed it.

I didn't miss anything. 'Exposure' doesn't mean the same as 'the light'.

Then you should have said as much instead of this song and dance on terminology. It was pretty clear what I meant, so why not advance the discussion instead of being deliberately obtuse?

It doesn't make much sense to base your assessment of what is 'fast' on exposure in cross format comparisons.

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Great Bustard
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Re: Fast lenses, and High ISO
In reply to bobn2, 3 months ago

bobn2 wrote:

Great Bustard wrote:

Chikoo wrote:

Great Bustard wrote:

Chikoo wrote:

ultimitsu wrote:

Chikoo wrote:

The only ability I see the fast lenses provide was actually a disadvantage that happened to become a feature, and that is shallow DoF, allowing for separation of subject from the background.

how is it a disadvantage when you can stop the lens down?

The purpose of designing larger apertures was to get more light in. The shallow DoF is a side effect or a by product of doing so.

Indeed, they both go hand-in-hand. This is a cornerstone of Equivalence.

I am sure the designers would like to have more light in without larger apertures. If they could they would.

Aside from wider apertures, there's more efficient sensors, longer shutter speeds, and/or flash -- each has its limitations.

In the end, if we want better performance, we have to adopt the one that human vision does, tons of signal processing. The eye is not ever so efficient as a photon collector, its lens isn't very fast and we aren't equipped with flash (well, not that kind of flash). Our vision is as good as it is because our built in processing takes these poor quality raws and uses prior experience of what things should look like to reconstruct good images from them.

The brain's processing goes into overboard when you're drunk, though -- what you wake up next to often looks very different than what you went home with. 

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Albert Silver
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Beer goggles
In reply to Great Bustard, 3 months ago

Great Bustard wrote:

bobn2 wrote:

Great Bustard wrote:

Chikoo wrote:

Great Bustard wrote:

Chikoo wrote:

ultimitsu wrote:

Chikoo wrote:

The only ability I see the fast lenses provide was actually a disadvantage that happened to become a feature, and that is shallow DoF, allowing for separation of subject from the background.

how is it a disadvantage when you can stop the lens down?

The purpose of designing larger apertures was to get more light in. The shallow DoF is a side effect or a by product of doing so.

Indeed, they both go hand-in-hand. This is a cornerstone of Equivalence.

I am sure the designers would like to have more light in without larger apertures. If they could they would.

Aside from wider apertures, there's more efficient sensors, longer shutter speeds, and/or flash -- each has its limitations.

In the end, if we want better performance, we have to adopt the one that human vision does, tons of signal processing. The eye is not ever so efficient as a photon collector, its lens isn't very fast and we aren't equipped with flash (well, not that kind of flash). Our vision is as good as it is because our built in processing takes these poor quality raws and uses prior experience of what things should look like to reconstruct good images from them.

The brain's processing goes into overboard when you're drunk, though -- what you wake up next to often looks very different than what you went home with.

Maybe some brilliant manufacturer will produce a new full-frame lens called "Beer goggles"

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Chikoo
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Re: "fast" is relative
In reply to bobn2, 3 months ago

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

Whether the point tko is making is wrong or not depends entirely on what you think is the definition of 'fast'. If you think that 'fast' is to do with exposure when comparing between formats, then he is wrong. However, that's not a very sensible point of view, so if you assume that he thinks that 'fast' means 'puts more light on the sensor' then he is right.

Fast has only one meaning:

Well that is obviously not true.

Shutter Speed, as in exposure time, the time value part of exposure.

Obviously it doesn't mean 'shutter speed', otherwise it would be 'shutter speed'. And 'fast' as used by people relates to aperture, not 'shutter speed'. So you are very obviously wrong. What it looks like is you have an agenda but haven't thought things through enough to successfully defend yourself, so you end up saying silly things like that. Let me help you out. A 'fast' lens is called a 'fast' lens because it allows you to set a 'fast' shutter speed. That begs the question, what would stop you setting any shutter speed that you want? My answer would be that you might not want to set too fast a shutter speed because it would result in a lower quality image than you would be satisfied with.

And that makes you just as much wrong as tko.

Or just as right, more likely in fact.

Photographic exposure is independent of media size.

Yes, I know that. The real question is how relevant is exposure when making cross format comparisons?

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Bob

Bob, fast is because it allows you faster shutter speeds. That was my original post. With high ISO do we need lenses with larger apertures just to allow more light when high ISO can achieve it for you with lesser light.

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Great Bustard
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Re: Understanding ISO
In reply to John Sheehy, 3 months ago

John Sheehy wrote:

Great Bustard wrote:

  • Photon Noise (noise from the light itself)
  • Read Noise (additional electronic noise from the sensor and supporting hardware)

So far as photon noise goes, modern sensors have a QE of right around 50%. What this means is that half of the light that makes it through the CFA (Color Filter Array) onto the pixel is recorded. Thus, for a Bayer CFA, there's only a stop more to go to 100% efficiency.

... in the green channel. The blue and red channels can improve even further. For future sensor geometries, red capture could conceivably increase by

I've always wondered what the difference in QE is between the different color channels -- do you know?

In other words, what we want is lower read noise, not "higher ISO". The thing is, though, a read noise of 2-3 electrons per pixel is already pretty low (considering that the pixels on FF DSLRs, for example, are able to produce signals of around 100,000 electrons), so why are high ISO photos noisy? The answer is simple: they get very little light, and less light means more noise.

2-3 electrons is not a big issue at base ISO, with big pixels, but for small pixels and and high ISOs it is tremendous read noise.

This is why I said below:

For sure, the read noise represents a kind of floor beyond which the noise in the photo quickly diminishes.

And of course, real world read noise does not look like gaussian noise created by a computer; it is highly correlated, visually, even if not significantly so, as a statistic.

I'd be interested in more info on that.  I've heard others say that read noise is pretty much gaussian (assuming we don't count banding as noise, since it is systematic).

In other words, it's not like sensors can keep on getting more and more efficient and low light photography will get less and less noisy. For sure, the read noise represents a kind of floor beyond which the noise in the photo quickly diminishes. But even with zero read noise, we are limited by the light itself.

That limit is much farther away, and is only limited in regard to how much we want to magnify the capture in display. Pure photon captures can work very well with very, very tiny signals if you do not need to display them large. They have no contrast issues in near-blacks, and no linearity problems down there, either.

The thing is, though, while lower read noise will certainly push the noise floor further out, the photo will still be rather noisy due to low signal.  For example, while we may be able to shift the "noise floor cliff" from ISO 25600 to 102400 with lower read noise, we're never going to make ISO 25600 look as good as ISO 3200.

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EinsteinsGhost
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Re: "fast" is relative
In reply to bobn2, 3 months ago

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

Whether the point tko is making is wrong or not depends entirely on what you think is the definition of 'fast'. If you think that 'fast' is to do with exposure when comparing between formats, then he is wrong. However, that's not a very sensible point of view, so if you assume that he thinks that 'fast' means 'puts more light on the sensor' then he is right.

Fast has only one meaning:

Well that is obviously not true.

You're wrong about that, unless you mean that it is also wrongly used for DOF based arguments. Fast is about speed (faster the lens, shorter the exposure time for identical conditions).

Shutter Speed, as in exposure time, the time value part of exposure.

Obviously it doesn't mean 'shutter speed', otherwise it would be 'shutter speed'. And 'fast' as used by people relates to aperture, not 'shutter speed'. So you are very obviously wrong. What it looks like is you have an agenda but haven't thought things through enough to successfully defend yourself, so you end up saying silly things like that. Let me help you out. A 'fast' lens is called a 'fast' lens because it allows you to set a 'fast' shutter speed. That begs the question, what would stop you setting any shutter speed that you want? My answer would be that you might not want to set too fast a shutter speed because it would result in a lower quality image than you would be satisfied with.

Faster aperture relates to faster time value which shows up with faster shutter speed. Sensor/format size has no bearing on this fact.

And that makes you just as much wrong as tko.

Or just as right, more likely in fact.

You wish to be right, and that is a fact. That you and tko are, isn't.

Photographic exposure is independent of media size.

Yes, I know that. The real question is how relevant is exposure when making cross format comparisons?

Irrelevant. That is why I argued against exposure equivalence.

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Great Bustard
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Re: "fast" is relative
In reply to EinsteinsGhost, 3 months ago

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

Whether the point tko is making is wrong or not depends entirely on what you think is the definition of 'fast'. If you think that 'fast' is to do with exposure when comparing between formats, then he is wrong. However, that's not a very sensible point of view, so if you assume that he thinks that 'fast' means 'puts more light on the sensor' then he is right.

Fast has only one meaning:

Well that is obviously not true.

You're wrong about that, unless you mean that it is also wrongly used for DOF based arguments. Fast is about speed (faster the lens, shorter the exposure time for identical conditions).

What shutter speed can you use on mFT at f/2 that you cannot use on FF at f/4?

Shutter Speed, as in exposure time, the time value part of exposure.

Obviously it doesn't mean 'shutter speed', otherwise it would be 'shutter speed'. And 'fast' as used by people relates to aperture, not 'shutter speed'. So you are very obviously wrong. What it looks like is you have an agenda but haven't thought things through enough to successfully defend yourself, so you end up saying silly things like that. Let me help you out. A 'fast' lens is called a 'fast' lens because it allows you to set a 'fast' shutter speed. That begs the question, what would stop you setting any shutter speed that you want? My answer would be that you might not want to set too fast a shutter speed because it would result in a lower quality image than you would be satisfied with.

Faster aperture relates to faster time value which shows up with faster shutter speed. Sensor/format size has no bearing on this fact.

What shutter speed can you use on mFT at f/2 that you cannot use on FF at f/4?

And that makes you just as much wrong as tko.

Or just as right, more likely in fact.

You wish to be right, and that is a fact. That you and tko are, isn't.

Photographic exposure is independent of media size.

Yes, I know that. The real question is how relevant is exposure when making cross format comparisons?

Irrelevant. That is why I argued against exposure equivalence.

Please tell us about the exposure differences here as they relate to the visual properties of the photo:

  • 50mm f/2 1/100 ISO 400 on mFT
  • 100mm f/2 1/100 ISO 400 on FF
  • 100mm f/4 1/100 ISO 1600 on FF
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bobn2
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Re: "fast" is relative
In reply to Albert Silver, 3 months ago

Albert Silver wrote:

bobn2 wrote:

Albert Silver wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

That was my point, though I think Bob missed it.

I didn't miss anything. 'Exposure' doesn't mean the same as 'the light'.

Then you should have said as much instead of this song and dance on terminology.

I simply assumed that you said what you meant and knew what you meant, and was telling you that you were wrong. Would you have preferred that I assumed that didn't know what you meant?

It was pretty clear what I meant,

Obviously not. Did you mean 'exposure' or 'light'. You said 'light' in which case you were wrong.

so why not advance the discussion instead of being deliberately obtuse?

Rather than me being obtuse, it seems that you don't know what you meant. If by 'light' you meant 'light' you were wrong. If by 'light' you meant 'exposure' then he was right and you were wrong to call him wrong. Since you were pulling up tko for supposedly being 'not entirely accurate' it was reasonable that you should be 'entirely accurate'. You weren't, either way.

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Great Bustard
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"the light"?
In reply to Albert Silver, 3 months ago

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

What do you mean by "the light will still be f/2"?  For a given scene luminance, shutter speed, and lens transmission, the density of light (exposure) projected on the sensor will be the same regardless of format, but not the total amount of light projected on the sensor.

So, in what way does the density of light falling on the sensor matter more than the total amount of light falling on the sensor?

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bobn2
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Re: "fast" is relative
In reply to EinsteinsGhost, 3 months ago

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

Whether the point tko is making is wrong or not depends entirely on what you think is the definition of 'fast'. If you think that 'fast' is to do with exposure when comparing between formats, then he is wrong. However, that's not a very sensible point of view, so if you assume that he thinks that 'fast' means 'puts more light on the sensor' then he is right.

Fast has only one meaning:

Well that is obviously not true.

You're wrong about that, unless you mean that it is also wrongly used for DOF based arguments. Fast is about speed (faster the lens, shorter the exposure time for identical conditions).

There are many possible meanings to the word 'fast' so your statement is wrong. Even if we narrow it down to photographic use as in 'a fast lens' you are still wrong, because quite clearly different people mean different things by it. It is also a colloquialism, so you can't refer to an official definition. So your statement was both untrue and displayed an intolerance for opinions other than your own.

Shutter Speed, as in exposure time, the time value part of exposure.

Obviously it doesn't mean 'shutter speed', otherwise it would be 'shutter speed'. And 'fast' as used by people relates to aperture, not 'shutter speed'. So you are very obviously wrong. What it looks like is you have an agenda but haven't thought things through enough to successfully defend yourself, so you end up saying silly things like that. Let me help you out. A 'fast' lens is called a 'fast' lens because it allows you to set a 'fast' shutter speed. That begs the question, what would stop you setting any shutter speed that you want? My answer would be that you might not want to set too fast a shutter speed because it would result in a lower quality image than you would be satisfied with.

Faster aperture relates to faster time value which shows up with faster shutter speed. Sensor/format size has no bearing on this fact.

Try reading this bit of what I wrote:

What would stop you setting any shutter speed that you want?

So, how and why does a large aperture lens 'show up with faster shutter speed'. If you're going to have any chance of winning this argument (don't worry too much, you haven't) you're going to have to display much clearer thinking than you are now.

And that makes you just as much wrong as tko.

Or just as right, more likely in fact.

You wish to be right, and that is a fact. That you and tko are, isn't.

You have singularly failed to demonstrate that we are`wrong, you simply assert it. Your argument gives out at 'faster aperture relates to faster time value which shows up with faster shutter speed', that's not taking you very far because you can't explain the why, where as we have. It allows a faster shutter speed for a given noise threshold. Your turn.

Photographic exposure is independent of media size.

Yes, I know that. The real question is how relevant is exposure when making cross format comparisons?

Irrelevant. That is why I argued against exposure equivalence.

Good, and since exposure is irrelevant, you can't say that a f/2 lens on FT is 'faster' than an f/4 lens on FF, since the only way it is 'faster' is if your definition of fast is based solely of exposure, which, as you've just said, is irrelevant when making cross format comparisons.

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EinsteinsGhost
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Re: "fast" is relative
In reply to Great Bustard, 3 months ago

Great Bustard wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

Whether the point tko is making is wrong or not depends entirely on what you think is the definition of 'fast'. If you think that 'fast' is to do with exposure when comparing between formats, then he is wrong. However, that's not a very sensible point of view, so if you assume that he thinks that 'fast' means 'puts more light on the sensor' then he is right.

Fast has only one meaning:

Well that is obviously not true.

You're wrong about that, unless you mean that it is also wrongly used for DOF based arguments. Fast is about speed (faster the lens, shorter the exposure time for identical conditions).

What shutter speed can you use on mFT at f/2 that you cannot use on FF at f/4?

Obviously, you didn't try to understand the point made. Let me make it simpler:

Scene brightness: 9 EV

ISO: 100

With these conditions, f/2 will have a faster shutter speed of about 1/4000s. An aperture of f/4 will give you 1/2000s. A larger or smaller sensor will not change that.

Shutter Speed, as in exposure time, the time value part of exposure.

Obviously it doesn't mean 'shutter speed', otherwise it would be 'shutter speed'. And 'fast' as used by people relates to aperture, not 'shutter speed'. So you are very obviously wrong. What it looks like is you have an agenda but haven't thought things through enough to successfully defend yourself, so you end up saying silly things like that. Let me help you out. A 'fast' lens is called a 'fast' lens because it allows you to set a 'fast' shutter speed. That begs the question, what would stop you setting any shutter speed that you want? My answer would be that you might not want to set too fast a shutter speed because it would result in a lower quality image than you would be satisfied with.

Faster aperture relates to faster time value which shows up with faster shutter speed. Sensor/format size has no bearing on this fact.

What shutter speed can you use on mFT at f/2 that you cannot use on FF at f/4?

Obviously, you didn't try to understand the point made. Let me make it simpler:

Scene brightness: 9 EV

ISO: 100

With these conditions, f/2 will have a faster shutter speed of about 1/4000s. An aperture of f/4 will give you 1/2000s. A larger or smaller sensor will not change that.

And that makes you just as much wrong as tko.

Or just as right, more likely in fact.

You wish to be right, and that is a fact. That you and tko are, isn't.

Photographic exposure is independent of media size.

Yes, I know that. The real question is how relevant is exposure when making cross format comparisons?

Irrelevant. That is why I argued against exposure equivalence.

Please tell us about the exposure differences here as they relate to the visual properties of the photo:

Same exposure on first and second (f/2, 1/100s, ISO 400). Lower exposure in third by two stops.

  • 50mm f/2 1/100 ISO 400 on mFT
  • 100mm f/2 1/100 ISO 400 on FF
  • 100mm f/4 1/100 ISO 1600 on FF
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Re: "fast" is relative
In reply to Chikoo, 3 months ago

Chikoo wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

Whether the point tko is making is wrong or not depends entirely on what you think is the definition of 'fast'. If you think that 'fast' is to do with exposure when comparing between formats, then he is wrong. However, that's not a very sensible point of view, so if you assume that he thinks that 'fast' means 'puts more light on the sensor' then he is right.

Fast has only one meaning:

Well that is obviously not true.

Shutter Speed, as in exposure time, the time value part of exposure.

Obviously it doesn't mean 'shutter speed', otherwise it would be 'shutter speed'. And 'fast' as used by people relates to aperture, not 'shutter speed'. So you are very obviously wrong. What it looks like is you have an agenda but haven't thought things through enough to successfully defend yourself, so you end up saying silly things like that. Let me help you out. A 'fast' lens is called a 'fast' lens because it allows you to set a 'fast' shutter speed. That begs the question, what would stop you setting any shutter speed that you want? My answer would be that you might not want to set too fast a shutter speed because it would result in a lower quality image than you would be satisfied with.

And that makes you just as much wrong as tko.

Or just as right, more likely in fact.

Photographic exposure is independent of media size.

Yes, I know that. The real question is how relevant is exposure when making cross format comparisons?

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Bob

Bob, fast is because it allows you faster shutter speeds.

Fine. That's what I said too. What determines how fast a shutter speed?

That was my original post. With high ISO do we need lenses with larger apertures just to allow more light when high ISO can achieve it for you with lesser light.

The only thing 'ISO' achieves is applying a given exposure to brightness function so that the image taken with your chosen exposure looks right at the end.

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Re: "fast" is relative
In reply to EinsteinsGhost, 3 months ago

EinsteinsGhost wrote:

Great Bustard wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

Whether the point tko is making is wrong or not depends entirely on what you think is the definition of 'fast'. If you think that 'fast' is to do with exposure when comparing between formats, then he is wrong. However, that's not a very sensible point of view, so if you assume that he thinks that 'fast' means 'puts more light on the sensor' then he is right.

Fast has only one meaning:

Well that is obviously not true.

You're wrong about that, unless you mean that it is also wrongly used for DOF based arguments. Fast is about speed (faster the lens, shorter the exposure time for identical conditions).

What shutter speed can you use on mFT at f/2 that you cannot use on FF at f/4?

Obviously, you didn't try to understand the point made. Let me make it simpler:

Scene brightness: 9 EV

ISO: 100

With these conditions, f/2 will have a faster shutter speed of about 1/4000s. An aperture of f/4 will give you 1/2000s. A larger or smaller sensor will not change that.

Shutter Speed, as in exposure time, the time value part of exposure.

Obviously it doesn't mean 'shutter speed', otherwise it would be 'shutter speed'. And 'fast' as used by people relates to aperture, not 'shutter speed'. So you are very obviously wrong. What it looks like is you have an agenda but haven't thought things through enough to successfully defend yourself, so you end up saying silly things like that. Let me help you out. A 'fast' lens is called a 'fast' lens because it allows you to set a 'fast' shutter speed. That begs the question, what would stop you setting any shutter speed that you want? My answer would be that you might not want to set too fast a shutter speed because it would result in a lower quality image than you would be satisfied with.

Faster aperture relates to faster time value which shows up with faster shutter speed. Sensor/format size has no bearing on this fact.

What shutter speed can you use on mFT at f/2 that you cannot use on FF at f/4?

Obviously, you didn't try to understand the point made. Let me make it simpler:

Scene brightness: 9 EV

ISO: 100

With these conditions, f/2 will have a faster shutter speed of about 1/4000s. An aperture of f/4 will give you 1/2000s. A larger or smaller sensor will not change that.

So, set ISO 200 and your lens is magically twice as fast. Perhaps it should be called the speed control.

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EinsteinsGhost
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Re: "fast" is relative
In reply to bobn2, 3 months ago

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

Whether the point tko is making is wrong or not depends entirely on what you think is the definition of 'fast'. If you think that 'fast' is to do with exposure when comparing between formats, then he is wrong. However, that's not a very sensible point of view, so if you assume that he thinks that 'fast' means 'puts more light on the sensor' then he is right.

Fast has only one meaning:

Well that is obviously not true.

You're wrong about that, unless you mean that it is also wrongly used for DOF based arguments. Fast is about speed (faster the lens, shorter the exposure time for identical conditions).

There are many possible meanings to the word 'fast' so your statement is wrong. Even if we narrow it down to photographic use as in 'a fast lens' you are still wrong, because quite clearly different people mean different things by it. It is also a colloquialism, so you can't refer to an official definition. So your statement was both untrue and displayed an intolerance for opinions other than your own.

I don't care about different people. I only care about why I would call a lens fast. It only relates to it allowing a lower exposure time. Ideally though, as I mentioned in one of my first posts in this thread, I would rather see T-stop being specified. But, most people probably don't know that either.

Shutter Speed, as in exposure time, the time value part of exposure.

Obviously it doesn't mean 'shutter speed', otherwise it would be 'shutter speed'. And 'fast' as used by people relates to aperture, not 'shutter speed'. So you are very obviously wrong. What it looks like is you have an agenda but haven't thought things through enough to successfully defend yourself, so you end up saying silly things like that. Let me help you out. A 'fast' lens is called a 'fast' lens because it allows you to set a 'fast' shutter speed. That begs the question, what would stop you setting any shutter speed that you want? My answer would be that you might not want to set too fast a shutter speed because it would result in a lower quality image than you would be satisfied with.

Faster aperture relates to faster time value which shows up with faster shutter speed. Sensor/format size has no bearing on this fact.

Try reading this bit of what I wrote:

What would stop you setting any shutter speed that you want?

So, how and why does a large aperture lens 'show up with faster shutter speed'. If you're going to have any chance of winning this argument (don't worry too much, you haven't) you're going to have to display much clearer thinking than you are now.

That you can do anything you want only distracts from the point about what fast lens is, and the role it plays in exposure. And "large aperture" has no meaning. A 200/4 lens has larger aperture than 35/1 but that does not make it a faster lens.

And that makes you just as much wrong as tko.

Or just as right, more likely in fact.

You wish to be right, and that is a fact. That you and tko are, isn't.

You have singularly failed to demonstrate that we are`wrong, you simply assert it. Your argument gives out at 'faster aperture relates to faster time value which shows up with faster shutter speed', that's not taking you very far because you can't explain the why, where as we have. It allows a faster shutter speed for a given noise threshold. Your turn.

Amen to that. It is a shame that a collective that is so vocal in this drama.

Photographic exposure is independent of media size.

Yes, I know that. The real question is how relevant is exposure when making cross format comparisons?

Irrelevant. That is why I argued against exposure equivalence.

Good, and since exposure is irrelevant, you can't say that a f/2 lens on FT is 'faster' than an f/4 lens on FF, since the only way it is 'faster' is if your definition of fast is based solely of exposure, which, as you've just said, is irrelevant when making cross format comparisons.

Eh, no. Stop collective thinking, and try to think for self: Not Exposure Equivalence But DOF Equivalence.

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Re: "fast" is relative
In reply to bobn2, 3 months ago

bobn2 wrote:

EinsteinsGhost wrote:

Great Bustard wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

Whether the point tko is making is wrong or not depends entirely on what you think is the definition of 'fast'. If you think that 'fast' is to do with exposure when comparing between formats, then he is wrong. However, that's not a very sensible point of view, so if you assume that he thinks that 'fast' means 'puts more light on the sensor' then he is right.

Fast has only one meaning:

Well that is obviously not true.

You're wrong about that, unless you mean that it is also wrongly used for DOF based arguments. Fast is about speed (faster the lens, shorter the exposure time for identical conditions).

What shutter speed can you use on mFT at f/2 that you cannot use on FF at f/4?

Obviously, you didn't try to understand the point made. Let me make it simpler:

Scene brightness: 9 EV

ISO: 100

With these conditions, f/2 will have a faster shutter speed of about 1/4000s. An aperture of f/4 will give you 1/2000s. A larger or smaller sensor will not change that.

Shutter Speed, as in exposure time, the time value part of exposure.

Obviously it doesn't mean 'shutter speed', otherwise it would be 'shutter speed'. And 'fast' as used by people relates to aperture, not 'shutter speed'. So you are very obviously wrong. What it looks like is you have an agenda but haven't thought things through enough to successfully defend yourself, so you end up saying silly things like that. Let me help you out. A 'fast' lens is called a 'fast' lens because it allows you to set a 'fast' shutter speed. That begs the question, what would stop you setting any shutter speed that you want? My answer would be that you might not want to set too fast a shutter speed because it would result in a lower quality image than you would be satisfied with.

Faster aperture relates to faster time value which shows up with faster shutter speed. Sensor/format size has no bearing on this fact.

What shutter speed can you use on mFT at f/2 that you cannot use on FF at f/4?

Obviously, you didn't try to understand the point made. Let me make it simpler:

Scene brightness: 9 EV

ISO: 100

With these conditions, f/2 will have a faster shutter speed of about 1/4000s. An aperture of f/4 will give you 1/2000s. A larger or smaller sensor will not change that.

So, set ISO 200 and your lens is magically twice as fast. Perhaps it should be called the speed control.

No, the lens isn't twice as fast. But, you've increased the "sensitivity" of the media, so the shutter speed can be twice as fast to achieve same brightness level in the image. Your change in exposure is only due to change in "sensitivity" of the media (we've discussed that several times before, haven't we? Funny though, you seem to be opposed to the idea of playing with exposure with ISO changes)

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Re: "the light"?
In reply to Great Bustard, 3 months ago

Great Bustard wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

What do you mean by "the light will still be f/2"? For a given scene luminance, shutter speed, and lens transmission, the density of light (exposure) projected on the sensor will be the same regardless of format, but not the total amount of light projected on the sensor.

Total light does not matter for correct exposure. It does not change the time value for which an exposure is made for a specific aperture value.

So, in what way does the density of light falling on the sensor matter more than the total amount of light falling on the sensor?

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Re: "fast" is relative
In reply to bobn2, 3 months ago

bobn2 wrote:

Chikoo wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

Albert Silver wrote:

tko wrote:

Remember that F4.0 is considered kind of slow on FF, but is equal to F2.0 on M43rds, which is considered "fast."

That's not entirely accurate. You are describing the depth of field equivalence, from one sensor to the next, not the light. f/2 on a m43rds may have the depth of field of f/4 on a full-frame, but the light will still be f/2.

The 'light' of a FF f/2 and a FT f/4 will be the same, which is the point he is making. In the end, given equally efficient sensors, you can achieve the same result at the same shutter speed using an f/4 on FF as you can on FT. The density of the light of the f/4 is one quarter but there is a sensor four times the area to collect it, so it ends up the same.

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Bob

The point tko is making is wrong. DOF equivalence applies, exposure equivalence does not (for the reason you state above).

Whether the point tko is making is wrong or not depends entirely on what you think is the definition of 'fast'. If you think that 'fast' is to do with exposure when comparing between formats, then he is wrong. However, that's not a very sensible point of view, so if you assume that he thinks that 'fast' means 'puts more light on the sensor' then he is right.

Fast has only one meaning:

Well that is obviously not true.

Shutter Speed, as in exposure time, the time value part of exposure.

Obviously it doesn't mean 'shutter speed', otherwise it would be 'shutter speed'. And 'fast' as used by people relates to aperture, not 'shutter speed'. So you are very obviously wrong. What it looks like is you have an agenda but haven't thought things through enough to successfully defend yourself, so you end up saying silly things like that. Let me help you out. A 'fast' lens is called a 'fast' lens because it allows you to set a 'fast' shutter speed. That begs the question, what would stop you setting any shutter speed that you want? My answer would be that you might not want to set too fast a shutter speed because it would result in a lower quality image than you would be satisfied with.

And that makes you just as much wrong as tko.

Or just as right, more likely in fact.

Photographic exposure is independent of media size.

Yes, I know that. The real question is how relevant is exposure when making cross format comparisons?

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Bob

Bob, fast is because it allows you faster shutter speeds.

Fine. That's what I said too. What determines how fast a shutter speed?

"Sensitivity" of the media, scene brightness and aperture. Nothing to do with media size.

That was my original post. With high ISO do we need lenses with larger apertures just to allow more light when high ISO can achieve it for you with lesser light.

The only thing 'ISO' achieves is applying a given exposure to brightness function so that the image taken with your chosen exposure looks right at the end.

Which is the point of exposure, to achieve a specific brightness level.

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