Fast lenses, and High ISO

Started 5 months ago | Discussions
EinsteinsGhost
Forum ProPosts: 11,977Gear list
Like?
Re: Why worship exposure?
In reply to Lee Jay, 5 months ago

Lee Jay 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.

-- hide signature --

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: Shutter Speed, as in exposure time, the time value part of exposure. And that makes you just as much wrong as tko.

Photographic exposure is independent of media size.

The fastest speed at which I can set my shutter speed is limited by the amount of noise I'll accept in the final image.

In other words, you don't understand what exposure entails.

The noise is driven by two things - the technology used in the sensor and the rest of the camera pipeline, and the TOTAL amount of light that falls of the sensor.

It makes no difference if that light is thinly spread out (slow f-stop, large sensor) or concentrated down (fast f-stop, small sensor). This is why f-stop equivalence holds across sensor sizes and why, say, ISO 400 and f/2 on 4/3 is equivalent to ISO 1600 and f/4 on full frame - they both produce the same image with the same noise from the same shutter speed given the same technology.

-- hide signature --

Lee Jay

 EinsteinsGhost's gear list:EinsteinsGhost's gear list
Sony Cyber-shot DSC-F828 Sony SLT-A55 Sony Alpha NEX-6 Sigma 18-250mm F3.5-6.3 DC OS HSM Sony 135mm F2.8 (T4.5) STF +12 more
Reply   Reply with quote   Complain
EinsteinsGhost
Forum ProPosts: 11,977Gear list
Like?
Re: "fast" is relative
In reply to bobn2, 5 months ago

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

So what? If the speed of `the lens is according to the shutter speed, then I've increased the speed of the lens by increasing the 'sensitivity' (I haven't, by the way) because I can now set a faster shutter speed, have I not?

Yes, you can change ISO and increase or decrease the shutter speed. What does it have to do with whether the lens is fast or slow?

You say that the speed of the lens is determined by the shutter speed it allows you to set. If you increase the ISO it 'allows' you to set a faster shutter speed, therefore under your definition, you have made the lens faster, because now you can set a faster shutter speed.

NO. You don't make a lens faster by increasing ISO.

So you keep saying, but that is not consistent with your definition of lens 'speed', that it allows you to use a fast shutter speed.

Nope. You simply don't get it. Unlike you, I won't run around screaming that my travel zoom is a fast lens when I use the camera at high ISO.

Well you should be, according to your own definition of 'fast'. I don't use your definition, so I don't have that problem. Remember we are here because you claimed that yours was the only definition of fast. Well, it had better not be because it's a pretty poor definition, as we've seen.

I agree. You don't use my definition. You should use mine: a lens is fast or slow based on relative aperture size (or t-stop, if specified). It has NOTHING to do with ISO setting in the camera which happens to be what your definition leads you.

You reduce exposure time value by increasing "sensitivity" of the sensor/film.

You really don't The sensitivity of the sensor never changes. You reduce exposure time value by deciding to use a smaller exposure.

Almost there! Where you didn't want to trust my prediction we were going.

So, why do you shoot Auto ISO?

By and large, I don't. I haven't found an Auto ISO which can be configured to do the right thing with respect to the exposure of the shot.

So, you chose ISO 100. And then found that since you could not use larger aperture with your lens being limited at f/4.5 and settled on 1/250s as the minimum shutter speed. You couldn't make your lens faster.

This is why people like to use the term "Exposure Triangle".

Many people get very misled by the 'Exposure Triangle'. Looks like you are one of them.

Actually the argument in favor of Exposure Triangle looks like this: "If you increase the ISO it 'allows' you to set a faster shutter speed"

That's not an argument in favour of the 'Exposure Triangle'. Firstly the 'triangle' geometry doesn't work. Secondly, the effect of increasing ISO is very different from the effect of increasing exposure. Increasing ISO resally doesn't 'allow' you to use a faster shutter speed, it just signifies that you've decided to use a lower exposure, so yiou can set a faster shutter speed. So now we come to the next question, why might one not allow oneself to use a smaller exposure?

Exposure Triangle is the basis of your argument: ISO, Aperture and Time Value being interrelated. According to you, increasing ISO makes time value shorter and according to you, as good as saying the lens is now faster.

But, here is my question: If you disagree with Exposure Triangle, why are you using it in your argument? That, if you increase ISO, it is as good as making a lens faster (or getting the same effect)? It is fundamental to Exposure Triangle.

Do you agree?

No

I do.

That doesn't surprise me at all.

But, what is happening there?

What has happened is that your lack of knowledge of the basics of photography has allowed you to be deceived by a popular but flawed mnemonic graphic into thinking that the ISO control is 'allowing' you to use a smaller exposure,when all that is happened is that you have decided to use a smaller exposure and used the ISO control to set the camera up for that exposure.

Aah the hypocrisy, of someone who says this (right below in bold). Awesome hypocrisy, or ignorance? Either way, amen to that.

Put it another way an f/2 at 200 ISO is as fast as an f/1.4 at 100 ISO because you can set the same shutter speed.

Shutter speed is as fast. An f/2 lens isn't any faster.

You need a new definition of 'fast' then, because you can set the same shutter speed with both.

And yet, you couldn't use a faster shutter speed because you claim having reached a limit on your lens being f/4.5 .

Of course I could have set a faster shutter speed, but that would have reduced exposure.

And why would that be?

In manual, I can set any combination of values that I like. Looks to me like you camera is controlling you, rather than you controlling your camera.

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)

I don't know what you mean. I don't remember ever having expressed opposition to 'playing with exposure with ISO changes'.

Trust me, you will be going there sometime very soon.

Why should I trust you when you say I have said things that I haven't?

You don't have to trust me.

I trust you to be wrong.

You don't have a choice.

I have a choice whether or not to trust you, though if I trust you to be wrong, I know that my trust will be rewarded amply.

I would add, you don't have a choice to deny either, because you must.

-- hide signature --

Bob

-- hide signature --

Bob

-- hide signature --

Bob

 EinsteinsGhost's gear list:EinsteinsGhost's gear list
Sony Cyber-shot DSC-F828 Sony SLT-A55 Sony Alpha NEX-6 Sigma 18-250mm F3.5-6.3 DC OS HSM Sony 135mm F2.8 (T4.5) STF +12 more
Reply   Reply with quote   Complain
EinsteinsGhost
Forum ProPosts: 11,977Gear list
Like?
Re: "the light"?
In reply to bobn2, 5 months ago

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

bobn2 wrote:

EinsteinsGhost wrote:

Great Bustard wrote:

EinsteinsGhost wrote:

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.

A competent mFT photographer with an EM10 + 12-40 / 2.8 shoots a scene at 25mm f/5.6 1/100 ISO 400. What settings would result

in the "correct exposure" if they had instead been using FF with a 6D + 24-70 / 2.8 VC?

For same exposure, any competent photographer would use f/5.6, 1/100 and ISO 400 on ANY format.

Would a competent photographer always use f/5.6, 1/100 and ISO 400 then?

-- hide signature --

Bob

No. The choice depends on scene. We're talking about a comparison of exposure here (don't deflect).

I'm not deflecting. The issue is how a competent photographer would select exposure.

And, a competent photographer would know that f/5.6, 1/100 at ISO 400 indicates a set of exposure parameters that is not bound by format.

That's not an answer. The photographer could choose f/2.8, 1/100, ISO 200; f/2.8, 1/50, ISO 100; f/11, 1/100, ISO 800; f/11, 1/200, ISO 1600 etc. Different exposures which lead to the same final image brightness. So which one should the competent photographer be choosing?

Same exposure as f/5.6, 1/100s, ISO 400.

No, they are all different exposures, one stop apart.

So, we should drop ISO from this argument, because it only defines final outcome, not exposure itself. In other words, exposure entails: Shutter Speed and Aperture Size. So, how in the world do you now manage to speed up a lens without using a larger aperture? Until now, you (and those few from the collective you've apparently impressed) have been claiming you can a lens becomes faster if you increase ISO.

Make up your mind, to enable a more coherent argument.

In fact, that is exactly what you arrived at with several possible combinations

As I said, they are all different exposures. So, your problem here is arguing from ignorance. You won't get much further unless you learn some photographic basics.

f/2, 1/200s and f/4, 1/50s are same exposures. Why would you disagree?

(something you don't seem to get in your own arguments above). Instead, there you claim, only one set of values provides you with "maximum" exposure.

Only one set here does give 'maximum' exposure, f/2.8, 1/50 ISO 100.Why wouldn't you use that?

As someone who you accuse to be ignorant of photography, allow me to educate you:

f/2.8 and 1/50s will give you the same exposure as f/4 and 1/25s. If you use a slower lens that goes to f/4 max, your best option is 1/25s for shutter speed. Now, if you want to bring in the concept of Exposure Triangle, that you can increase ISO to compensate for aperture and/or time, be my guest.

We don't have enough information to know - maybe not enough DOF at f/2.,8, maybe too much camera shake at 1/50 - assuming that the competent photographer chose f/5.6, 1/100 for a good reason. Still, maybe you should go and learn some basic photography before we continue. First, what 'exposure' means.

The topic is: Exposure.

-- hide signature --

Bob

 EinsteinsGhost's gear list:EinsteinsGhost's gear list
Sony Cyber-shot DSC-F828 Sony SLT-A55 Sony Alpha NEX-6 Sigma 18-250mm F3.5-6.3 DC OS HSM Sony 135mm F2.8 (T4.5) STF +12 more
Reply   Reply with quote   Complain
EinsteinsGhost
Forum ProPosts: 11,977Gear list
Like?
Re: You missed the question.
In reply to jonas ar, 5 months ago

jonas ar wrote:

EinsteinsGhost wrote:

Because a competent photographer knows exposure is not dependent on format. It is dependent on: ISO, Aperture and Shutter values for a given scene brightness. That is it.

According to wikipedia photographic exposure is the amount of light (the image plane illuminance times the exposure time) reaching a photographic film (and you may substitute film with "sensor" if you like).

I can see how the aperture and shutterspeed (and the scene brightness) affect the exposure in this defintion, but please do explain how ISO affects the amount of light reaching the sensor. Or do you not agree with wikipedia on the definition of exposure?

I am surprised you didn't ask bob this question. He can make a lens faster by using a different ISO. I can't.

That being said, there is a place for ISO setting. Exposure by itself is only time value (shutter speed) and aperture value. However, how much (and for how long) an exposure is needed also considers "ISO".

Can you not see that changing the ISO is fundamentally different from changing the amount of light recorded?

If you still disagree with my point above, tell me how you use ISO, or if you don't use it at all.

Do you really think that we change the exposure when we use the exposure slider in raw processors (or modulate the image brightness of the developed picture in other ways by software)?

You compensate for exposure differences by doing so. You make those adjustments since you realized that the image was either under-exposed or over-exposed to achieve what you wanted. Any other reason you use that slider?

 EinsteinsGhost's gear list:EinsteinsGhost's gear list
Sony Cyber-shot DSC-F828 Sony SLT-A55 Sony Alpha NEX-6 Sigma 18-250mm F3.5-6.3 DC OS HSM Sony 135mm F2.8 (T4.5) STF +12 more
Reply   Reply with quote   Complain
EinsteinsGhost
Forum ProPosts: 11,977Gear list
Like?
Re: You forgot something.
In reply to Great Bustard, 5 months ago

Great Bustard wrote:

EinsteinsGhost wrote:

Great Bustard wrote:

EinsteinsGhost wrote:

Great Bustard wrote:

EinsteinsGhost wrote:

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.

Obviously, you do not understand ISO. Why would a FF photographer feel compelled to shoot the same ISO as the mFT photographer?

I don't see a reason for a FF photographer feeling compelled to shoot an ISO 100 shot at ISO 3200.

Neither do I:

I think this image from your gallery agrees:

Its not ISO 100 image. It is an ISO 400 image.

I see both photographers to shoot at the lowest possible ISO and in this case, it will be the base ISO.

It's fair to say that if f/2 meters at 1/4000, and thus f/4 would meter for 1/1000, then, sure, 1/1000 is more than likely to be "fast enough" in almost all circumstances. What happens with f/2 meters at 1/400? Will f/4 at 1/100 be "fast enough"?

Not necessarily (depends on subject). Which is when you might increase the ISO (as you or your camera did, in the image above).

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

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

That is correct! However, you forgot to tell us how this relates to the visual properties of the photo.

The visual property that an exposure is all about is brightness of the scene. For same brightness, same exposure is expected. With higher ISO (third bullet above), you're doing just that, increasing brightness by two stop to compensate for reduced exposure by two stops.

So what we see here, really, is that exposure is merely part of the equation:

  • Exposure (photons / mm²) = Sensor Illuminance (photons / mm² / s) · Time (s)
  • Brightness (photons / mm²) = Exposure (photons / mm²) · Amplification (unitless)
  • Total Light (photons) = Exposure (photons / mm²) · Effective Sensor Area (mm²)
  • Total Light Collected (electrons) = Total Light (photons) · QE (electrons / photon)
 EinsteinsGhost's gear list:EinsteinsGhost's gear list
Sony Cyber-shot DSC-F828 Sony SLT-A55 Sony Alpha NEX-6 Sigma 18-250mm F3.5-6.3 DC OS HSM Sony 135mm F2.8 (T4.5) STF +12 more
Reply   Reply with quote   Complain
EinsteinsGhost
Forum ProPosts: 11,977Gear list
Like?
Re: You missed the question.
In reply to jonas ar, 5 months ago

jonas ar wrote:

jrtrent wrote:

jonas ar wrote:

EinsteinsGhost wrote:

Because a competent photographer knows exposure is not dependent on format. It is dependent on: ISO, Aperture and Shutter values for a given scene brightness. That is it.

According to wikipedia photographic exposure is the amount of light (the image plane illuminance times the exposure time) reaching a photographic film (and you may substitute film with "sensor" if you like).

I can see how the aperture and shutterspeed (and the scene brightness) affect the exposure in this defintion, but please do explain how ISO affects the amount of light reaching the sensor.

The light falling on the scene and the speed of the film are conditions that help us determine what exposure settings (aperture and shutter speed combinations) are needed. The sunny f/16 rule tells us that for a front-lit subject on a bright, sunny day, f/16 plus a shutter speed that is the reciprocal of the film speed should result in a good exposure. ISO therefore affects the amount of light we want to reach the film (or sensor). For Kodachrome 200, you might use f/16 and 1/200 (or some equivalent pair such as f/8 and 1/800); for Fuji Astia, f/16 and 1/100 would be correct (or, again, some other equivalent pair such as f/8 and 1/400).

The ISO rating of a film was only specified for a very specific proces. If you changed the processing you would change the ISO.

Or, perhaps the other way around: if you needed to change the ISO, you had to use a different process that enabled development of film for that ISO.

Precisely as is the case for digital processing og raw files.

As bobn2 has patiently explained it imay not be a very good practice to let the exposure follow the ISO (instead of letting the ISO follow the exposure) because it will often lead to a lower exposure (and hence more noise) than strictkly required.

 EinsteinsGhost's gear list:EinsteinsGhost's gear list
Sony Cyber-shot DSC-F828 Sony SLT-A55 Sony Alpha NEX-6 Sigma 18-250mm F3.5-6.3 DC OS HSM Sony 135mm F2.8 (T4.5) STF +12 more
Reply   Reply with quote   Complain
EinsteinsGhost
Forum ProPosts: 11,977Gear list
Like?
Re: You missed the question.
In reply to Austinian, 5 months ago

Austinian wrote:

jonas ar wrote:

EinsteinsGhost wrote:

Because a competent photographer knows exposure is not dependent on format. It is dependent on: ISO, Aperture and Shutter values for a given scene brightness. That is it.

According to wikipedia photographic exposure is the amount of light (the image plane illuminance times the exposure time) reaching a photographic film (and you may substitute film with "sensor" if you like).

I can see how the aperture and shutterspeed (and the scene brightness) affect the exposure in this defintion, but please do explain how ISO affects the amount of light reaching the sensor. Or do you not agree with wikipedia on the definition of exposure?

Can you not see that changing the ISO is fundamentally different from changing the amount of light recorded?

Do you really think that we change the exposure when we use the exposure slider in raw processors (or modulate the image brightness of the developed picture in other ways by software)?

I've been waiting for somebody to bring this up. If history is any guide, now the real fun begins.

I think the latest image in your gallery can provide some answers, taken at ISO 1600. Why?

PS. I was there, three days earlier.

 EinsteinsGhost's gear list:EinsteinsGhost's gear list
Sony Cyber-shot DSC-F828 Sony SLT-A55 Sony Alpha NEX-6 Sigma 18-250mm F3.5-6.3 DC OS HSM Sony 135mm F2.8 (T4.5) STF +12 more
Reply   Reply with quote   Complain
EinsteinsGhost
Forum ProPosts: 11,977Gear list
Like?
Excuse me for interrupting the theatre...
In reply to bobn2, 5 months ago

bobn2 wrote:

They are important when they are important, but not before they are important. The problem we have is that people think that ISO is the implementation details. That misunderstanding is not their fault, it is because a great many sources, including this site have told them that it is so. So, the first thing people need to get is what ISO actually is...

That makes me wonder how I must respond to those who suggest that if you increase the ISO from 100 to 200, you can make a lens faster since the exposure is faster.

But you may resume the theater I'd promised (and you didn't want to trust me on that).

 EinsteinsGhost's gear list:EinsteinsGhost's gear list
Sony Cyber-shot DSC-F828 Sony SLT-A55 Sony Alpha NEX-6 Sigma 18-250mm F3.5-6.3 DC OS HSM Sony 135mm F2.8 (T4.5) STF +12 more
Reply   Reply with quote   Complain
Lee Jay
Forum ProPosts: 45,299Gear list
Like?
Re: Why worship exposure?
In reply to EinsteinsGhost, 5 months ago

EinsteinsGhost wrote:

Lee Jay 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.

-- hide signature --

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: Shutter Speed, as in exposure time, the time value part of exposure. And that makes you just as much wrong as tko.

Photographic exposure is independent of media size.

The fastest speed at which I can set my shutter speed is limited by the amount of noise I'll accept in the final image.

In other words, you don't understand what exposure entails.

You really learned nothing from this?

Exposure is illuminance-time product, by definition. Illuminance is controlled by f-stop, and time is controlled by shutter speed. ISO has nothing to do with it.

http://www.kodak.com/global/en/consumer/products/techInfo/aa9/aa9.shtml

"Exposure
The quantity of light allowed to act on a photographic material; product of the intensity (controlled by the lens opening) and the duration (controlled by the shutter speed or enlarging time) of light striking the film or paper."

http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/4500/EXPOSURE/EV-overview.html

Exposure Value = log2(aperture^2/shutter speed)

The noise is driven by two things - the technology used in the sensor and the rest of the camera pipeline, and the TOTAL amount of light that falls of the sensor.

It makes no difference if that light is thinly spread out (slow f-stop, large sensor) or concentrated down (fast f-stop, small sensor). This is why f-stop equivalence holds across sensor sizes and why, say, ISO 400 and f/2 on 4/3 is equivalent to ISO 1600 and f/4 on full frame - they both produce the same image with the same noise from the same shutter speed given the same technology.

Read it again, as it seemed to go right over your head.

Hint: Do you really think you can get faster shutter speeds with my f/2.6 cell phone than with my f/4 full-frame? For acceptable noise, I have to expose the cell phone at a maximum exposure index of 200, while I can accept and EI of 12,800 for the full-frame. That's why the full-frame is faster at f/4 than the cell phone is at f/2.6.

-- hide signature --

Lee Jay

 Lee Jay's gear list:Lee Jay's gear list
Canon IXUS 310 HS Canon PowerShot SX260 HS Canon EOS 5D Canon EOS 20D Canon EOS 550D +23 more
Reply   Reply with quote   Complain
EinsteinsGhost
Forum ProPosts: 11,977Gear list
Like?
Re: Why worship exposure?
In reply to Lee Jay, 5 months ago

Lee Jay wrote:

EinsteinsGhost wrote:

Lee Jay 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.

-- hide signature --

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: Shutter Speed, as in exposure time, the time value part of exposure. And that makes you just as much wrong as tko.

Photographic exposure is independent of media size.

The fastest speed at which I can set my shutter speed is limited by the amount of noise I'll accept in the final image.

In other words, you don't understand what exposure entails.

You really learned nothing from this?

I have, that some of you are pretty good actors.

Exposure is illuminance-time product, by definition. Illuminance is controlled by f-stop, and time is controlled by shutter speed. ISO has nothing to do with it.

http://www.kodak.com/global/en/consumer/products/techInfo/aa9/aa9.shtml

"Exposure
The quantity of light allowed to act on a photographic material; product of the intensity (controlled by the lens opening) and the duration (controlled by the shutter speed or enlarging time) of light striking the film or paper."

http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/4500/EXPOSURE/EV-overview.html

Exposure Value = log2(aperture^2/shutter speed)

Seems like you've been worshipping exposure enough to dwell deeply on it (unless you're simply googling and posting links).

Or, are you completely atheistic to what you just presented above?

The noise is driven by two things - the technology used in the sensor and the rest of the camera pipeline, and the TOTAL amount of light that falls of the sensor.

It makes no difference if that light is thinly spread out (slow f-stop, large sensor) or concentrated down (fast f-stop, small sensor). This is why f-stop equivalence holds across sensor sizes and why, say, ISO 400 and f/2 on 4/3 is equivalent to ISO 1600 and f/4 on full frame - they both produce the same image with the same noise from the same shutter speed given the same technology.

Read it again, as it seemed to go right over your head.

Hint: Do you really think you can get faster shutter speeds with my f/2.6 cell phone than with my f/4 full-frame? For acceptable noise, I have to expose the cell phone at a maximum exposure index of 200, while I can accept and EI of 12,800 for the full-frame. That's why the full-frame is faster at f/4 than the cell phone is at f/2.6.

-- hide signature --

Lee Jay

 EinsteinsGhost's gear list:EinsteinsGhost's gear list
Sony Cyber-shot DSC-F828 Sony SLT-A55 Sony Alpha NEX-6 Sigma 18-250mm F3.5-6.3 DC OS HSM Sony 135mm F2.8 (T4.5) STF +12 more
Reply   Reply with quote   Complain
Keyboard shortcuts:
FForum MMy threads