Fast lenses, and High ISO

Started 2 months ago | Discussions
Great Bustard
Forum ProPosts: 23,547
Like?
Re: Understanding ISO
In reply to PalmettoFellow, 2 months ago

PalmettoFellow wrote:

Great Bustard wrote:

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? 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.

That said, should they be called Fast Lenses or Shallow Lenses?

When people say things like "In this age of ever increasing ISO...", what they mean is "In this age of ever more efficient sensors". This is not a small, or pedantic point. The reason is that there are two primary sources of noise in a photo:

  • 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 terms of read noise, most modern sensors are at around 2-3 electrons per pixel at high ISO settings. The role played by the ISO setting is that higher ISOs result in lower read noise (up to a point) due to the analog amplification applied to the signal through the ADC -- Analog to Digital Converter. That means, for example, that ISO 3200 is less noisy than ISO 100 pushed 5 stops. However, most all sensors are ISOless by ISO 3200 (some are ISOless right from base ISO), so that ISO 25600, for example, has the exact same noise as ISO 3200 pushed 3 stops.

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.

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.

So, do we still "need" fast lenses? Inasmuch as we want less noise for any given shutter speed, yes, we do. Of course, that lower noise comes with the concomitant effect of a more shallow DOF, which sucks for those that want a deeper DOF in low light for a given shutter speed.

No, but I have a pretty decent wand.  Wanna see a pic? 

Reply   Reply with quote   Complain
Great Bustard
Forum ProPosts: 23,547
Like?
Re: Understanding ISO
In reply to Austinian, 2 months ago

Austinian wrote:

mosswings wrote:

Good recasting of the subject, GB.

And the reason why sensors aren't getting rapidly better anymore.

Which is bad news for those expecting major sensor improvements in the immediate future, but good news for those fearing their existing gear will soon become obsolete.

Lowering the read noise, however, is important for increasing pixel counts. For example, the read noise at high ISOs for modern sensors is typically in the 2-3 electron range. Let's see the effect this has on various pixel counts over the same area of the photo (I like to use the µphoto, which is a millionth of a photo -- for example, 1 µphoto on a 24 MP sensor is 24 pixels) using a read noise of 2.5 electrons / pixel:

12 MP: 8.7 electrons / µphoto

24 MP: 12.2 electrons / µphoto

48 MP: 17.3 electrons / µphoto

96 MP: 24.5 electrons / µphoto

As we can see, every doubling of pixel count increases the read noise by 41%, assuming that the read noise per pixel is the same. If the read noise pixel were to be half as much for 4x as many pixels, then the read noise µphoto would remain unchanged.

So, there additional improvements in sensor tech with regards to read noise are very important with regards to increasing pixel counts.

Reply   Reply with quote   Complain
dosdan
Regular MemberPosts: 373Gear list
Like?
Re: Fast lenses, and High ISO
In reply to Chikoo, 2 months ago

Chikoo wrote:

1. AF is done with the lens wide open: faster lenses AF much better in poor light.

Mike

Interestingly, I have had more focus misses with the lens wide open.

That's because the results of either a missed focus or BF/FF mis-adjustment are usually much more obvious with shallow DOF.

Dan.

 dosdan's gear list:dosdan's gear list
Pentax K20D Pentax K-5 Pentax Q Pentax K-01 Pentax K-3
Reply   Reply with quote   Complain
Great Bustard
Forum ProPosts: 23,547
Like?
Re: Fast lenses, and High ISO
In reply to dosdan, 2 months ago

dosdan wrote:

Chikoo wrote:

1. AF is done with the lens wide open: faster lenses AF much better in poor light.

Mike

Interestingly, I have had more focus misses with the lens wide open.

That's because the results of either a missed focus or BF/FF mis-adjustment are usually much more obvious with shallow DOF.

In addition to the fact that wide open photography more usually occurs in lower light.  That said, on a DSLR, the lens focuses wide open, regardless.

Reply   Reply with quote   Complain
Austinian
Senior MemberPosts: 1,378Gear list
Like?
Re: Understanding ISO
In reply to Great Bustard, 2 months ago

Great Bustard wrote:

Austinian wrote:

mosswings wrote:

Good recasting of the subject, GB.

And the reason why sensors aren't getting rapidly better anymore.

Which is bad news for those expecting major sensor improvements in the immediate future, but good news for those fearing their existing gear will soon become obsolete.

Lowering the read noise, however, is important for increasing pixel counts. For example, the read noise at high ISOs for modern sensors is typically in the 2-3 electron range. Let's see the effect this has on various pixel counts over the same area of the photo (I like to use the µphoto, which is a millionth of a photo -- for example, 1 µphoto on a 24 MP sensor is 24 pixels) using a read noise of 2.5 electrons / pixel:

12 MP: 8.7 electrons / µphoto

24 MP: 12.2 electrons / µphoto

48 MP: 17.3 electrons / µphoto

96 MP: 24.5 electrons / µphoto

As we can see, every doubling of pixel count increases the read noise by 41%, assuming that the read noise per pixel is the same. If the read noise pixel were to be half as much for 4x as many pixels, then the read noise µphoto would remain unchanged.

So, there additional improvements in sensor tech with regards to read noise are very important with regards to increasing pixel counts.

Ah! I'd read that for identical technologies, sensor area was the most important factor, but it was implied that it wasn't the only factor. Good to know this is another.

What other significant aspects should digital camera buyers consider, and is such specific sensor information readily available?

 Austinian's gear list:Austinian's gear list
Sony a77 II Sigma 10-20mm F4-5.6 EX DC HSM Sony DT 55-300mm F4.5-5.6 SAM Sony DT 35mm F1.8 SAM Sony DT 16-50mm F2.8 SSM +3 more
Reply   Reply with quote   Complain
pavi1
Veteran MemberPosts: 4,959Gear list
Like?
Re: Fast lenses, and High ISO
In reply to Chikoo, 2 months ago

Chikoo wrote:

That said, should they be called Fast Lenses or Shallow Lenses?

They will always be called fast lenses and even if you have ISO 10 million, ISO can not produce 1.4.

-- hide signature --

Everything happens for a reason. #1 reason: poor planning
WSSA #44

Reply   Reply with quote   Complain
Great Bustard
Forum ProPosts: 23,547
Like?
Re: Understanding ISO
In reply to Austinian, 2 months ago

Austinian wrote:

Great Bustard wrote:

Austinian wrote:

mosswings wrote:

Good recasting of the subject, GB.

And the reason why sensors aren't getting rapidly better anymore.

Which is bad news for those expecting major sensor improvements in the immediate future, but good news for those fearing their existing gear will soon become obsolete.

Lowering the read noise, however, is important for increasing pixel counts. For example, the read noise at high ISOs for modern sensors is typically in the 2-3 electron range. Let's see the effect this has on various pixel counts over the same area of the photo (I like to use the µphoto, which is a millionth of a photo -- for example, 1 µphoto on a 24 MP sensor is 24 pixels) using a read noise of 2.5 electrons / pixel:

12 MP: 8.7 electrons / µphoto

24 MP: 12.2 electrons / µphoto

48 MP: 17.3 electrons / µphoto

96 MP: 24.5 electrons / µphoto

As we can see, every doubling of pixel count increases the read noise by 41%, assuming that the read noise per pixel is the same. If the read noise pixel were to be half as much for 4x as many pixels, then the read noise µphoto would remain unchanged.

So, there additional improvements in sensor tech with regards to read noise are very important with regards to increasing pixel counts.

Ah! I'd read that for identical technologies, sensor area was the most important factor, but it was implied that it wasn't the only factor. Good to know this is another.

What other significant aspects should digital camera buyers consider, and is such specific sensor information readily available?

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

Sensorgen has used DxOMark data to get the QE and read noise for a lot of sensors. However, differences in the dyes in the CFA can result in a greater QE by letting more light in with the result of less luminance noise at the expense of greater color noise (there may also be issues with metamerism, although that's more complex than merely the transmissivity of the dyes).

For example, I compared the Canon 6D at ISO 6400 to the Olympus EM5 at ISO 1600:

http://www.dpreview.com/reviews/image-comparison?attr18=daylight&attr13_0=canon_eos6d&attr13_1=oly_em5&attr13_2=canon_eos5dmkiii&attr13_3=canon_eos5dmkiii&attr15_0=raw&attr15_1=raw&attr15_2=raw&attr15_3=raw&attr16_0=6400&attr16_1=1600&attr16_2=6400&attr16_3=6400&normalization=full&widget=1&x=0.060211267605633806&y=-0.8281959827294914

Here are sensorgen’s figures for the 6D and EM5:

  • 6D: QE = 50%, read noise @ ISO 6400 = 2 electrons / pixel = 9 electrons / µphoto
  • EM5: QE = 53%, read noise @ ISO 1600 = 2.6 electrons / pixel = 10.4 electrons / µphoto

That's about as identical as it gets, yet the EM5 was cleaner when they should be all but indistinguishable. Assuming that the exposures for the DPR's test scene were exactly two stops apart, I’m thinking the reason for the EM5’s cleaner appearance is due to less color noise. So, I did own conversions and processing to both photos.

As it turned out, they did end up looking all but identical in terms of noise (well, I had to lower the red gamma and overall gamma on the 6D photo a bit to get the colors nearly the same, too).

So, I don't know if that means that color noise isn't a big deal, or that the color noise in this particular example was close enough to where NR (noise reduction) resulted in no significant loss of detail.

Then there's the issue of microlens efficiency (DxOMark's F-stop blues, discussed in more detail here), which can have a decided impact on how much light falling on the sensor makes it into the pixel at wide apertures.

For astrophotographers, or any other photographers that use long exposures, thermal noise is a big deal, so that's another factor to consider which I did not list above.

Reply   Reply with quote   Complain
ultimitsu
Veteran MemberPosts: 5,577
Like?
Re: Fast lenses, and High ISO
In reply to Chikoo, 2 months ago

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?

Reply   Reply with quote   Complain
Chikoo
Senior MemberPosts: 1,630Gear list
Like?
Re: Fast lenses, and High ISO
In reply to ultimitsu, 2 months ago

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.

Reply   Reply with quote   Complain
Great Bustard
Forum ProPosts: 23,547
Like?
Re: Fast lenses, and High ISO
In reply to Chikoo, 2 months ago

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.

Reply   Reply with quote   Complain
Chikoo
Senior MemberPosts: 1,630Gear list
Like?
Re: Fast lenses, and High ISO
In reply to Great Bustard, 2 months ago

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.

Reply   Reply with quote   Complain
Great Bustard
Forum ProPosts: 23,547
Like?
Re: Fast lenses, and High ISO
In reply to Chikoo, 2 months ago

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.

Reply   Reply with quote   Complain
dosdan
Regular MemberPosts: 373Gear list
Like?
Re: Fast lenses, and High ISO
In reply to Great Bustard, 2 months ago

Great Bustard wrote:

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

Or longer shutter speeds by proxy: combining multiple exposures.

Dan.

 dosdan's gear list:dosdan's gear list
Pentax K20D Pentax K-5 Pentax Q Pentax K-01 Pentax K-3
Reply   Reply with quote   Complain
ultimitsu
Veteran MemberPosts: 5,577
Like?
Re: Fast lenses, and High ISO
In reply to Chikoo, 2 months ago

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.

You did not answer the question.

A F/1.4 lens can stop down to at the least F/16, often F/32. That ability is not different to that of an F/5.6 lens. So I am asking you again, how is it a disadvantage when you can stop the lens down?

At best, you could argue one cannot always make use of the large aperture advantage, specifically, when deeper DOF is required. But that is not what you said.

Reply   Reply with quote   Complain
bobn2
Forum ProPosts: 29,954
Like?
Re: Fast lenses, and High ISO
In reply to Great Bustard, 2 months ago

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.

-- hide signature --

Bob

Reply   Reply with quote   Complain
Austinian
Senior MemberPosts: 1,378Gear list
Like?
Re: Understanding ISO
In reply to Great Bustard, 2 months ago

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)?

Sensorgen has used DxOMark data to get the QE and read noise for a lot of sensors. However, differences in the dyes in the CFA can result in a greater QE by letting more light in with the result of less luminance noise at the expense of greater color noise (there may also be issues with metamerism, although that's more complex than merely the transmissivity of the dyes).

For example, I compared the Canon 6D at ISO 6400 to the Olympus EM5 at ISO 1600:

http://www.dpreview.com/reviews/image-comparison?attr18=daylight&attr13_0=canon_eos6d&attr13_1=oly_em5&attr13_2=canon_eos5dmkiii&attr13_3=canon_eos5dmkiii&attr15_0=raw&attr15_1=raw&attr15_2=raw&attr15_3=raw&attr16_0=6400&attr16_1=1600&attr16_2=6400&attr16_3=6400&normalization=full&widget=1&x=0.060211267605633806&y=-0.8281959827294914

Here are sensorgen’s figures for the 6D and EM5:

  • 6D: QE = 50%, read noise @ ISO 6400 = 2 electrons / pixel = 9 electrons / µphoto
  • EM5: QE = 53%, read noise @ ISO 1600 = 2.6 electrons / pixel = 10.4 electrons / µphoto

That's about as identical as it gets, yet the EM5 was cleaner when they should be all but indistinguishable. Assuming that the exposures for the DPR's test scene were exactly two stops apart, I’m thinking the reason for the EM5’s cleaner appearance is due to less color noise. So, I did own conversions and processing to both photos.

As it turned out, they did end up looking all but identical in terms of noise (well, I had to lower the red gamma and overall gamma on the 6D photo a bit to get the colors nearly the same, too).

So, I don't know if that means that color noise isn't a big deal, or that the color noise in this particular example was close enough to where NR (noise reduction) resulted in no significant loss of detail.

This reminds me of something else, and leads me off into a bit of a detour...

Back when one of the lengthy ISO/exposure disputes was raging, I decided to test the (to me at the time) counterintuitive notion that given fairly ISOless sensors (like my then Sony A57), images at ISO 100 brightened in RAW processing would be very similar to the same images shot at ISO 1600.

Indeed this proved to be largely true, and I was duly impressed. However, there was some additional shadow color noise in the 'pushed' ISO 100 images.

(Is this the result of slightly-less-than-perfect "ISOlessness" of the sensor, or artifacts of RAW development, or what? It did seem that some RAW processors did better than others at this, but I don't know what kind of noise reduction they might have been doing.)

As a result of these crude tests, plus info I found on the Net, I kept my ISO between 100 (max dynamic range?) and 400 (min noise?) on that camera.

The A77 II is new enough that I haven't run all the tests I should, but judging from what I see on DxOmark, the ISO 100-800 range may behave similarly.

Comments?

Then there's the issue of microlens efficiency (DxOMark's F-stop blues, discussed in more detail here), which can have a decided impact on how much light falling on the sensor makes it into the pixel at wide apertures.

For astrophotographers, or any other photographers that use long exposures, thermal noise is a big deal, so that's another factor to consider which I did not list above.

I suspect that given our existing battery life constraints, active cooling for DSLR sensors isn't in most photographers' future.

 Austinian's gear list:Austinian's gear list
Sony a77 II Sigma 10-20mm F4-5.6 EX DC HSM Sony DT 55-300mm F4.5-5.6 SAM Sony DT 35mm F1.8 SAM Sony DT 16-50mm F2.8 SSM +3 more
Reply   Reply with quote   Complain
Chikoo
Senior MemberPosts: 1,630Gear list
Like?
Re: Fast lenses, and High ISO
In reply to ultimitsu, 2 months ago

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.

You did not answer the question.

A F/1.4 lens can stop down to at the least F/16, often F/32. That ability is not different to that of an F/5.6 lens. So I am asking you again, how is it a disadvantage when you can stop the lens down?

At best, you could argue one cannot always make use of the large aperture advantage, specifically, when deeper DOF is required. But that is not what you said.

I apologize for nor answering your question directly. If you look at photo history, a picture contains everything you see through the viewfinder esp rangefinders. With larger apertures, that is not the case. The foreground and background blurs away. Stepping down takes care of that, but then it is no longer a fast lens.

Reply   Reply with quote   Complain
Chikoo
Senior MemberPosts: 1,630Gear list
Like?
Re: Fast lenses, and High ISO & Transmission losses
In reply to EinsteinsGhost, 2 months ago

EinsteinsGhost 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? 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.

That said, should they be called Fast Lenses or Shallow Lenses?

The issue is primarily due to f-stop performing double duty in photography (video appropriately uses t-stop for exposure).

F-stop is primarily about DOF, and t-stop is about speed. But since most photography lenses are not specified in t-stop (in fact, the only lens I know, and have it, is Sony 135mm f/2.8[T4.5] STF where the t-stop is also specified).

Transmission losses. That is a wonderful aspect that I did not give due consideration in this rambling of mine, and opens up the door to a whole another discussion regarding flash & studio lighting. If you have your camera + flash program setting based upon a certain transmission loss, then you will most likely see over exposure or underexposure if using the camera's built in program features when you switch lenses for the same aperture and shutter speed. Which also brings into the picture, the number of elements. The more the elements, the higher the transmission losses for the same optical material in use.

Reply   Reply with quote   Complain
ultimitsu
Veteran MemberPosts: 5,577
Like?
Re: Fast lenses, and High ISO
In reply to Chikoo, 2 months ago

Chikoo 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.

You did not answer the question.

A F/1.4 lens can stop down to at the least F/16, often F/32. That ability is not different to that of an F/5.6 lens. So I am asking you again, how is it a disadvantage when you can stop the lens down?

At best, you could argue one cannot always make use of the large aperture advantage, specifically, when deeper DOF is required. But that is not what you said.

I apologize for nor answering your question directly. If you look at photo history, a picture contains everything you see through the viewfinder esp rangefinders. With larger apertures, that is not the case. The foreground and background blurs away. Stepping down takes care of that, but then it is no longer a fast lens.

You still did not answer the question. It has already been established that large aperture isnt always an advantage, but where stopping down is needed, large aperture lens can do so. So the question is still left unanswered:

How is it a disadvantage?

Reply   Reply with quote   Complain
mosswings
Veteran MemberPosts: 5,913Gear list
Like?
Re: Fast lenses, and High ISO
In reply to bobn2, 2 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.

-- hide signature --

Bob

We also have to consider that the eye has the ability to adapt both while scanning and in response to existing conditions. But the mechanics of perception in the eye-brain system are indeed awesome.

 mosswings's gear list:mosswings's gear list
Olympus XZ-1 Nikon D90 Nikon D7100 Nikon AF-S DX Nikkor 18-105mm f/3.5-5.6G ED VR Nikon AF-S Nikkor 70-300mm f/4.5-5.6G VR +1 more
Reply   Reply with quote   Complain
Keyboard shortcuts:
FForum MMy threads