'ISO-free' test: How far can the A7 files be pushed?

Played around with my A7 last night, and made some exposures from ISO 100 to 25600 just to find out how much the files can be pushed to keep highlight detail and still keep acceptable shadow detail. This is essential for high dynamic range/high contrast scenes when not usiong HDR technique. I did this to find out if I can handle the A7 as an "ISO-free" camera or not.

I did expose at ISO 100 wit the same shutter speed and aperture as correctly exposed ISO 400, ISO 1600, ISO 6400 and ISO 25600 files, like this:

• ISO 100: 2 sec at f:8
• ISO 400: 1/2 sec at f:8 and ISO 100 with the same exposure (-2 stop)
• ISO 1600: 1/8 sec at f:8 and ISO 100 with the same exposure (-4 stop)
• ISO 6400: 1/30 sec at f:8 and ISO 100 with the same exposure (-6 stop)
• ISO 25600: 1/125 sec at f:8 and ISO 100 with the same exposure (-8 stop)

From my finding the exposure can be pushed about 4-6 stops from ISO 100 and still keep good shadow detail. But there is obviously going on a lot of noise reduction and color adjustment before the raw files are written, and also some shadow detail is lots at low ISO. So the sensor for the A7 can probably not be said to be truly "ISO-free - anyway, Sony is doing a phenomenal job with noise reduction and color correction before raw with the high ISO files!

What is impressive though (and expected) is that the pushed ISO 100 files contain almost the same shadow detail as the high ISO files, shown in the extremely pushed examples below (pushed way beond ISO 25600). The pushed files from ISO 100 are much more muddy than the pushed ISO 6400 samples, due to on-chip high ISO noise reduction and obviously also a lot of color corretion. Still the shadow detail is present from the ISO 100 files, which looks completely black when opened in the raw converter (Photoshop CS/ACR).

So what to conclude? The best strategy is to use the needed ISO settings for the A7 to get the cleanest possible shadow data. If I need extra dynamic range to keep maximum highlight detail, like street views at eveninng/night and astrophotography, I can underexpose 3-4 stops from a given ISO setting and then push the files at post processing. But for scenes with normal contrast, I would highly recommend using the appropriate ISO setting and expose so that the highlights are kept, which in most cases should be "correct" exposure.

Here are some example from the ISO 6400 exposure, compared to a pushed ISO 100 exposure (same shutter speed and aperture for both, 1/30 sec at f:8 - the ISO 100 file looked black when opened with the raw converter):


Exposure 1/30 sec at f:8: Guess if this is ISO 6400 or pushed from a heavily underexposed ISO 100 file ...


... or if this is the ISO 6400 exposure or the ISO pushed 100 exposure?


100% crops from correct exposed ISO 6400 file to the left and pushed ISO 100 files to the right. The pushed files are a bit more muddy in the shadows with smeared detail, much more noise and a red color cast.


Extremely pushed files - way beond ISO 25600! 100% crops from the ISO 6400 file to the left and the insanely pushed ISO 100 files to the right. Almost all shadow detail is present in the ISO 100 files but noise and color cast is hard to deal with at processing!

You outlined her, and then you responded to my questions, a few months ago re exposing for highlights then moving the shadow control to the right and then the Clarity control in Lightroom. I have done a lot of shots in Europe recently in which I have played with this technique.

Here are a couple of examples. Both were shot handheld in extremely low light. A couple of years ago I would not have even bothered to take the cap off the camera unless I had a tripod with me in this light, especially the second shot (and if I had had a tripod, I'd never have dreamed of being able to stop the movement to any extent at all.)

















--
Mike Fewster
Adelaide Australia

Mike Fewster said:

You outlined her, and then you responded to my questions, a few months ago re exposing for highlights then moving the shadow control to the right and then the Clarity control in Lightroom. I have done a lot of shots in Europe recently in which I have played with this technique.

Here are a couple of examples. Both were shot handheld in extremely low light. A couple of years ago I would not have even bothered to take the cap off the camera unless I had a tripod with me in this light, especially the second shot (and if I had had a tripod, I'd never have dreamed of being able to stop the movement to any extent at all

Click to expand...

Great samples, Mike! Good job!

Normally I use ISO 200 as my "base ISO", but for this thest I went down to ISO 100. Sure, there are a lot of detail available in the files, but I find it hard to keep up with the job Sony is doing on noise reduction and color correction at the highest ISO settings.

That said, for normal size pictures/prints and everyday use you can push the A7 files many exposure steps, since the noise and muddy colors will drown into the shadow areas.

Nice to know the camera, uh?

Are you shooting with the a7's High ISO NR and Long Exposure NR on in camera? I turn both of those off and do a better job of denoising in Lightroom 5.5. I'm going to PP anyway, so I might as well do the denoising myself and get it the way I want it reather than the way Sony guesses is best. But that is just me and my workflow. I like total control.

W5JCK said:

Are you shooting with the a7's High ISO NR and Long Exposure NR on in camera? I turn both of those off and do a better job of denoising in Lightroom 5.5.

Click to expand...

I do the same, I turn them off. For astrophoto I use manual dark frames (and flats).

Nordstjernen said:

W5JCK said:

Are you shooting with the a7's High ISO NR and Long Exposure NR on in camera? I turn both of those off and do a better job of denoising in Lightroom 5.5.

Click to expand...

I do the same, I turn them off. For astrophoto I use manual dark frames (and flats).

Click to expand...

Nice example of the inherent problems of under exposing and then raising the shadows slider. I wonder how A7 NR ON plus LR denoise VS. only LR denoise would look in a match up.

ferrellmc said:

Nice example of the inherent problems of under exposing and then raising the shadows slider.

Click to expand...

I think my test touches the complexity and possibilities of 'correct' and pushed exposure rather than showing problems. You need to push low to medium ISO files quite a lot before image quality turns so low that image content/how we perceive the final picture is affected.

File quality is what we get from the camera, and is limited by the content of the raw file. As photographers we should go for the exposure strategy and post processing procedures that make us get the most from the quality. ;-)

W5JCK said:

Are you shooting with the a7's High ISO NR and Long Exposure NR on in camera? I turn both of those off and do a better job of denoising in Lightroom 5.5. I'm going to PP anyway, so I might as well do the denoising myself and get it the way I want it reather than the way Sony guesses is best. But that is just me and my workflow. I like total control.

Click to expand...

I'm confused. Are you guys saying that the "High ISO NR" is applied before RAW file is generated? I always thought it is a NR setting for JPEG.

joe6pack said:

I'm confused. Are you guys saying that the "High ISO NR" is applied before RAW file is generated? I always thought it is a NR setting for JPEG.

Click to expand...

No, high ISO nosie reduction is something you turn on or off. With this feature you can choose between smoothing out the noise or keep ultra-fine detail at the cost of more visible noise.

For all sensors there are going on a lot of processing and noise removal before raw. Better to reduce signal errors as early as possible to get the cleanest raw files! If there were no such on-chip noise reduction, you would never have bought a Sony camera, I think! You would have been scared away by the amount of image noise.

Nordstjernen said:

ferrellmc said:

Nice example of the inherent problems of under exposing and then raising the shadows slider.

Click to expand...

I think my test touches the complexity and possibilities of 'correct' and pushed exposure rather than showing problems. You need to push low to medium ISO files quite a lot before image quality turns so low that image content/how we perceive the final picture is affected.

File quality is what we get from the camera, and is limited by the content of the raw file. As photographers we should go for the exposure strategy and post processing procedures that make us get the most from the quality. ;-)

Click to expand...

What has impressed me lately is how much can be extracted from underexposed film, when it is carefully digitized. Negatives that would have been unusable in the traditional darkroom can come up quite well.

Not as far as you can push the sensor output, but much further than you would expect.

Nordstjernen said:

Mike Fewster said:

You outlined her, and then you responded to my questions, a few months ago re exposing for highlights then moving the shadow control to the right and then the Clarity control in Lightroom. I have done a lot of shots in Europe recently in which I have played with this technique.

Here are a couple of examples. Both were shot handheld in extremely low light. A couple of years ago I would not have even bothered to take the cap off the camera unless I had a tripod with me in this light, especially the second shot (and if I had had a tripod, I'd never have dreamed of being able to stop the movement to any extent at all

Click to expand...

Great samples, Mike! Good job!

Normally I use ISO 200 as my "base ISO", but for this thest I went down to ISO 100. Sure, there are a lot of detail available in the files, but I find it hard to keep up with the job Sony is doing on noise reduction and color correction at the highest ISO settings.

That said, for normal size pictures/prints and everyday use you can push the A7 files many exposure steps, since the noise and muddy colors will drown into the shadow areas.

Nice to know the camera, uh?

Click to expand...

Have you tried MFNR? Your limited to jpeg of course but it is an effective way to deal with extremely low light handheld. The detail is preserved and no noise at very high iso.

Nordstjernen said:

joe6pack said:

I'm confused. Are you guys saying that the "High ISO NR" is applied before RAW file is generated? I always thought it is a NR setting for JPEG.

Click to expand...

No, high ISO nosie reduction is something you turn on or off. With this feature you can choose between smoothing out the noise or keep ultra-fine detail at the cost of more visible noise.

For all sensors there are going on a lot of processing and noise removal before raw. Better to reduce signal errors as early as possible to get the cleanest raw files! If there were no such on-chip noise reduction, you would never have bought a Sony camera, I think! You would have been scared away by the amount of image noise.

Click to expand...

At least on my NEX-3N, High ISO NR is either Normal or Low. Did you tested the difference to confirm that High ISO NR is applied to RAW?

PVCdroid said:

Have you tried MFNR? Your limited to jpeg of course but it is an effective way to deal with extremely low light handheld. The detail is preserved and no noise at very high iso.

Click to expand...

Yes, I also have tripods, but this is a test to learn the files to know, down to the last useable shadow bit of data.

joe6pack said:

At least on my NEX-3N, High ISO NR is either Normal or Low. Did you tested the difference to confirm that High ISO NR is applied to RAW?

Click to expand...

This test is not about in-camera noise reduction.

Nordstjernen said:

joe6pack said:

I'm confused. Are you guys saying that the "High ISO NR" is applied before RAW file is generated? I always thought it is a NR setting for JPEG.

Click to expand...

No, high ISO nosie reduction is something you turn on or off. With this feature you can choose between smoothing out the noise or keep ultra-fine detail at the cost of more visible noise.

For all sensors there are going on a lot of processing and noise removal before raw. Better to reduce signal errors as early as possible to get the cleanest raw files! If there were no such on-chip noise reduction, you would never have bought a Sony camera, I think! You would have been scared away by the amount of image noise.

Click to expand...

Just keeping the record straight. Base on info from another thread:

High ISO NR is NOT applied to RAW. The options are Normal (Auto) / Low / Off (depends on camera)

Long Exposure NR is applied to RAW. The options are On/Off.

Nordstjernen wrote:

Nordstjernen said:

Played around with my A7 last night, and made some exposures from ISO 100 to 25600 just to find out how much the files can be pushed to keep highlight detail and still keep acceptable shadow detail. This is essential for high dynamic range/high contrast scenes when not [using] HDR technique. I did this to find out if I can handle the A7 as an "ISO-free" camera or not.

Click to expand...

Good job. Although you pushed it further than you'd actually do it in practice, you've demonstrated a truth about the a7's sensor.

There are ways to test a camera to see if it is "ISO-free" (aka "ISOless), and the a7 passes at least one of those tests:

Nordstjernen said:

So what to conclude? The best strategy is to use the needed ISO settings for the A7 to get the cleanest possible shadow data. If I need extra dynamic range to keep maximum highlight detail, like street views at eveninng/night and astrophotography, I can underexpose 3-4 stops from a given ISO setting and then push the files at post processing. But for scenes with normal contrast, I would highly recommend using the appropriate ISO setting and expose so that the highlights are kept, which in most cases should be "correct" exposure.

Click to expand...

There are many possible exposure strategies the classic is ETTR. However, ETTR is only an effective way to improve the SNR in the final image if you leave the in-camera ISO setting at the base level.

Unfortunately, there are many photographic situations where ETTR at base ISO produces unacceptable f-stops or shutter speeds. Dim light, camera or subject motion, depth-of-field considerations, and other practicalities conspire to keep the photographer from getting enough photons to the sensor. What’s the best strategy in that all-too-common circumstance? There are two poles.

The first is to set an acceptable combination of f-stop and shutter speed, then crank up the ISO to keep the histogram on the right. This has the advantage of allowing the photographer to use the same technique regardless of the lighting level, but it has some disadvantages.

• The sacrifice of headroom and margin for error with no gain in image quality.
• Slower, more fiddly exposure calculations (trial exposures, spotmetering, etc.) when they’re not necessary.

The opposite approach is to leave the ISO setting in the camera at base ISO, and when it’s impractical to expose to the right, just underexpose and fix things in your favorite raw development program. This also has disadvantages:

• The preview image may be too dark to see.
• In the case of cameras with electronic viewfinders, the finder may be useless, or nearly so.
• The photographer may be unaware of how far underexposed the shot is, and not know if acceptable results can be obtained in post=processing.
• The SNR may be slightly short of optimum (this is the least significant problem, and the effects may be so small that it’s unreasonable to consider it a problem at all).

As is true with most things in life, the extreme approaches are not the best ones. Here's a rather complicated way to split the difference:


I'm sure there are better compromises between simplicity and accuracy. Suggestions?

Jim

PVCdroid said:

PVCdroid said:

Mike Fewster said:

You outlined her, and then you responded to my questions, a few months ago re exposing for highlights then moving the shadow control to the right and then the Clarity control in Lightroom. I have done a lot of shots in Europe recently in which I have played with this technique.

Here are a couple of examples. Both were shot handheld in extremely low light. A couple of years ago I would not have even bothered to take the cap off the camera unless I had a tripod with me in this light, especially the second shot (and if I had had a tripod, I'd never have dreamed of being able to stop the movement to any extent at all

Click to expand...

Great samples, Mike! Good job!

Normally I use ISO 200 as my "base ISO", but for this thest I went down to ISO 100. Sure, there are a lot of detail available in the files, but I find it hard to keep up with the job Sony is doing on noise reduction and color correction at the highest ISO settings.

That said, for normal size pictures/prints and everyday use you can push the A7 files many exposure steps, since the noise and muddy colors will drown into the shadow areas.

Nice to know the camera, uh?

Click to expand...

Have you tried MFNR? Your limited to jpeg of course but it is an effective way to deal with extremely low light handheld. The detail is preserved and no noise at very high iso.

Click to expand...

It is about two months since I took the shot of the flag performer and I have taken a lot of shots since then. It is quite likely, on reflection, that I was using the Hand held Twilight mode when I shot and then used the shadow/clarify push technique to get the image. I think that is why the camera was able to freeze the flags to the extent it did, it used one of the frames, then enhanced them. I was totally stunned to get any image at all. It was extremely dark with just a few lights scattered around the periphery and nothing at all directly on the performer. I am about to catch a plane but when I get some time I'll investigate the original file and try to figure what actually happened. I used the shadow/clarity technique for sure however.

Nordstjernen said:

Extremely pushed files - way beond ISO 25600! 100% crops from the ISO 6400 file to the left and the insanely pushed ISO 100 files to the right. Almost all shadow detail is present in the ISO 100 files but noise and color cast is hard to deal with at processing!

Click to expand...

Are you sure that the increased colour cast is present in the raw file and is not just a result of ACR applying different amounts of colour noise reduction to the two photos?

If you turn of colour noise reduction completely in ACR, I will not be surprised if the colour noise is exactly the same.

At least that is how Lightroom works, and since the Develop module in Lightroom is basically ACR with another GUI, I would expect ACR to work the same way.

It seems to me that Adobe is adjusting the scaling of the colour noise reduction slider behind the scenes as a function of the ISO selection, so the default slider value of 25 will apply less reduction to an ISO 100 photo than to an ISO 6400 photo. This actually works rather well in daily use, but when the shadows in a low ISO photo are pushed, the slider scaling is wrong.

I really wish that they would scale the slider as a function of actual, physical exposure and not as a function of selected ISO.

Allan Olesen said:

Are you sure that the increased colour cast is present in the raw file and is not just a result of ACR applying different amounts of colour noise reduction to the two photos?

Click to expand...

Did a new test with the same files. Opened both (ISO 6400 and ISO 100, same exposure) with no noise reduction at all in Photoshop. It looks like most data is preserved in the ISO 100 raw file, but that it takes really some skills to squeeze the deepes shadow info from this raw file with ACR, if possible at all.

I don't exactly know how ACR handles the shadow data when files are pushed this much, but when I am back home after my summer holiday I will do some tests with a raw converter that handles the full tonal range.

I will also test if everything works better from ISO 200, in case ISO 100 is lower than base ISO.

Allan Olesen said:

If you turn of colour noise reduction completely in ACR, I will not be surprised if the colour noise is exactly the same.

Click to expand...

No, the color noise is very different - much less noise in the ISO 6400 file, and also much better deep shadow detail. My guess is that there are something going in at ac/dc, and that some shadow data might be skipped at low ISO. Makes sense, since we never push the shadows this much for ordinary work.

I find your comments interesting, and the results quite informative.

Here are my results from no noise reduction at all with ACR:


100% crops: Files from ISO 6400 and ISO 100 with identical exposure settings. The ISO 100 files was pushed to get a similar result as the ISO 6400 file, and no noise reduction was applied for ACR. Noise reduction for the ISO 100 files shown in the middle was applied with Photoshop.