Fast lenses, and High ISO

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Chikoo
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Fast lenses, and High ISO
3 months ago

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?

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

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).

That being said, while faster lens can make us worry less about high ISO, having high ISO access without worries can allow you even more freedom. In fact, my first digital camera is still with me 10.5 years later by virtue of its faster zoom lens and infra red capability: Sony Cybershot F828. It has a 28-200mm equiv lens with f/2-2.8. This allowed to extend the life of the camera even though I would use ISO 400 as I would ISO 6400 on my APSc cameras today. A vast majority of shots involve ISO 64 or 100.

Now, I took some available light family portraits 750ft below ground at Carlsbad Caverns recently using Sony NEX-6. There isn't much light there (in this case, there was some light from the cafe but still too dark to see in person). I had Minolta 50/1.4 on Speedbooster, which gave me an effective 35mm f/1 lens. I used ISO 3200 and still had only 1/30s for shutter speed (could have improved it a bit with spot metering but some of the ambiance would be lost). The scene brightness value was -5EV. This is an example of when just a superfast lens or high ISO capability worked better when combined.

Would I have loved having Sony a7s instead? You bet! Would have gotten same exposure at ISO 6400 which is impressively clean and composed in that camera.

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mike703
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Re: Fast lenses, and High ISO
In reply to Chikoo, 3 months ago

Yes for two reasons.

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

2. Even with today's high-ISO capabilities i find myself sometimes wanting to shootat the limit of what the camera can do:

1/30 sec, f/2.8, ISO 6400

Best wishes

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Bob Tullis
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As with so many things, "It depends' applies here as well.
In reply to Chikoo, 3 months ago

Factors include how far one pushes 'low light (or thinks in terms of low light)', and how refined a finish is acceptable.

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mosswings
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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? 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?

Some have suggested "bright" lenses.

In the days of film, large-aperture lenses were coveted in no small part because film sensitivities were so low: ISO 400 was a very fast film stock, and the images it produced were often grainy and blah. Kodachrome 25 or 64 were great, but you had to use a tripod in anything but bright conditions.

Today, digital's insanely high ISO capabilities have made slower lenses (f4-f5.6) practical general purpose options and have opened up existing-light photographic possibilities that didn't exist previously. One must remember that every increment in ISO reduces the DR, SNR, and color rendition quality of the captured image, so that there is still a practical maximum ISO for any desired image quality. DXO uses a standard of 10 stops of DR for acceptable IQ, and this is reached in modern sensors at around ISO 800-3200 depending on sensor size and manufacturer.

Fast lenses have always brought to the table generally better imaging performance at all apertures than that provided by the f4-f5.6 general purpose kit lenses. But most casual photographers are unwilling to accept the size, weight, and price penalty for that improved imaging performance, so ISO is a godsend for the camera manufacturers, as it enables them to offer practical utility at a tolerable price and size.

Yes, fast lenses offer shallower DOF, but they offer the serious photographer signficant advantages in what counts - image quality, AF speed, and durability. I should note, however, that it's quite possible to make an extremely high quality slow lens. Consider the Nikon 70-200 f/4 and the 70-200 f/2.8. The f/4 meets and in some cases exceeds the quality of the f/2.8, long recognized as a benchmark of IQ, but in a smaller, lighter, and more affordable package. It is limited in its light gathering capability, so you won't find it at nighttime sporting events or in the most demanding situations. It is also 5 times the cost of the 55-200 f/4-5.6, but you are paying for the visibly better image quality.

For those applications where DOF needs to be deep - such as landscapes - a slower lens stopped down to f/8 will perform quite well. Landscape photogs can get away with a slower "consumer" lens...but they benefit from the IQ of the higher end lenses.

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Lee Jay
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Re: Fast lenses, and High ISO
In reply to Chikoo, 3 months ago

Chikoo wrote:

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

Depends on how dark it is where you are shooting.  I've shot at ISO 12,800 at f/1.4 and been three stops short of the shutter speed I needed.

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MediaArchivist
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Samyang "Cine" lenses
In reply to EinsteinsGhost, 3 months ago

In general, you are correct that measurement in "T" stops is uncommon for still camera lenses. The Samyang "Cine" line has stepless apertures labeled in T/stop values. The lenses are pretty much the same as the non-stepless (stepped?) versions, but nonetheless is another (rare) example.

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Chris R-UK
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Fast lenses and sensor size
In reply to Chikoo, 3 months ago

Fast lenses are clearly less important on MF and FF cameras because the larger sensor allow for higher ISO settings and better DoF control.

However, as sensors get smaller, fast lenses as measured by the f-number became much more important because high ISO performance is worse and depth of field control is more difficult.

That is why Voigtlander has a range of f/0.95 lenses for M4/3 and there are superzooms like the Panasonic FZ200 with f/2.8 over the entire 24x zoom focal length range.

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tko
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you still need high--and higher--ISO
In reply to Chikoo, 3 months ago

People simple don't realize how easy it is to get into trouble. Shoot action when gets a little dark, and all of sudden you need ISO12800--or higher. Deep shadows between buildings, inside Churches, at dusk (the best hour to shoot.)

Returning from Europe, I had hundreds of images shot at ISO 12800 with shutter speeds down to 1/10th of a second. I was using relatively slow lenses (F4 to F5.6.) If I had faster lenses (which I didn't because I was traveling light) I could have shot ISO 3200 or lower. Much better image quality.

Yes, the lens still makes a difference, depending on your shooting needs.

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?

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tko
tko
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"fast" is relative
In reply to Chris R-UK, 3 months ago

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

A F0.95 lens on M43rds is equal in performance to a F2.0 lens on FF, which (for a prime on FF) is pretty slow.

We won't even talk about how slow the superzooms are in FF terms.

Chris R-UK wrote:

Fast lenses are clearly less important on MF and FF cameras because the larger sensor allow for higher ISO settings and better DoF control.

However, as sensors get smaller, fast lenses as measured by the f-number became much more important because high ISO performance is worse and depth of field control is more difficult.

That is why Voigtlander has a range of f/0.95 lenses for M4/3 and there are superzooms like the Panasonic FZ200 with f/2.8 over the entire 24x zoom focal length range.

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hotdog321
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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? 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?

Since they've always been called fast lenses, I think we should stick with established tradition in the interest of simplicity and to avoid confusion. Why borrow trouble?

You opening question is more interesting. Back in the film days, we would eagerly pay hundreds or thousands of dollars more for a lens that was 1/3 to 1 stop faster. This miniscule difference often spelled the difference between getting the picture or missing it altogether in sports or news photography. 3200 film, for instance, was often so "crunchy" that it was unsuitable even for newsprint.

But these days we use those wonderful modern digital sensors that allow us to shoot at 3200-6400 or higher and still capture really excellent images. Bokeh aficionados might still desire really fast lenses, but most of us can probably do without.

For instance, I recently bought Canon's 16-35 f/4L IS lens because of massive improvements in edge sharpness. My old 16-35 f/2.8 (version 1) is going into a drawer as backup. I'm a photojournalist, but I'm not worried about the f/4 speed. I wish it was f/2.8, but it's not a deal-breaker.

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Chris R-UK
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Re: "fast" is relative
In reply to tko, 3 months ago

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."

A F0.95 lens on M43rds is equal in performance to a F2.0 lens on FF, which (for a prime on FF) is pretty slow.

We won't even talk about how slow the superzooms are in FF terms.

I don't disagree with you.  I was just making the point that "low f-number lenses" become more and more important on smaller sensors.

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Great Bustard
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Understanding 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? 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.

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bosjohn21
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Re: Fast lenses, and High ISO
In reply to Chikoo, 3 months ago

while I think using a shallow depth of field has become a cleche its still useful. But I think more importantly the fast lens also moves down its so called sweet spot two or so stops below wide open where the optical performance is at its best. Using a fast lens also means having better sharpness and because the lens will deliver optimum performance two stops faster than a normal f 2.8 or sof this less distortion in conjunction with hi iso,

on the other hand Lens design is all compromises and the price paid for f1.4 is a nth less resolution in the center and a bit more on the edges,  In most photograph images this will be meaningless.

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Chikoo
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Re: Fast lenses, and High ISO
In reply to mike703, 3 months ago

Yes for two reasons.

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

2. Even with today's high-ISO capabilities i find myself sometimes wanting to shootat the limit of what the camera can do:

1/30 sec, f/2.8, ISO 6400

Best wishes

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

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bosjohn21
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Re: Fast lenses, and High ISO
In reply to Chikoo, 3 months ago

Chikoo wrote:

Yes for two reasons.

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

2. Even with today's high-ISO capabilities i find myself sometimes wanting to shootat the limit of what the camera can do:

1/30 sec, f/2.8, ISO 6400

Best wishes

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

I know you didn't ask for any input about this image but I think is very interesing and well done. It looks like a movie set but no matter your pov is wonderful and your processing is greatl

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

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.

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

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.

Good recasting of the subject, GB. And the reason why sensors aren't getting rapidly better anymore.

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Austinian
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Re: Understanding ISO
In reply to mosswings, 3 months ago

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.

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mike703
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many thanks John (n/t)
In reply to bosjohn21, 3 months ago
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