Higher ISO vs Lower ISO underexposure and PS adjustment

[Stan Raucher]

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Lets assume that you want to photograph with an M8 in a low-light situation with a particular shutter speed and aperture.

 

Has anyone compared the image quality at high ISO with the correct exposure versus lower ISO with a 1 stop underexposure followed by adjusting the exposure of the dng file in Photoshop or Lightroom?

 

For example, which of the following would give a better quality image:

 

ISO 1250 1/125 sec f/2 (correct exposure) with no adjustment of dng file versus ISO 640 1/125 sec f/2 (1 stop underexposed) with a +1 stop adjustment of dng file in Photoshop or Lightroom.

 

Thanks,

 

Stan

[robertwright]

Lets assume that you want to photograph with an M8 in a low-light situation with a particular shutter speed and aperture.

 

Has anyone compared the image quality at high ISO with the correct exposure versus lower ISO with a 1 stop underexposure followed by adjusting the exposure of the dng file in Photoshop or Lightroom?

 

For example, which of the following would give a better quality image:

 

ISO 1250 1/125 sec f/2 (correct exposure) with no adjustment of dng file versus ISO 640 1/125 sec f/2 (1 stop underexposed) with a +1 stop adjustment of dng file in Photoshop or Lightroom.

 

Thanks,

 

Stan

 

without doing the side by side, but in terms of what I have seen so far from the camera that I use every day, my subjective experience is that within +1 or maybe as far as +2, you are likely to get similar files, with an edge to underexpose/overdevelop. The reason is not so much shadow noise, although I have seen that it is lower on lower iso regardless of what you do, but the difference is at the top, what is likely to happen is that you will blow a highlight, and it will be unrecoverable.

 

the M8 has led me to this counterintuitve as far as digital orthodoxy goes, approach. In the beginning I was lamenting the lack of highlight dynamic range, as I was exposing like I always used to for canon dslr's that is, overexposing and darkening the image in processing, and recovering blown highlights.

 

On the M8 that does not work, what I get are posterizations in highlight transitions, and I think this is the result of the encoding they have chosen, to optimize for the shadows. Now I am going to the limit of the highlights but not over. I will let a bare bulb for example go over, but I will be very careful of a window in a backlight situation for example. I will not expose correctly for the foreground, but let it go darker, and pull it up in post.

 

This to me seems to auger the point that it is better to underexpose and "push" rather than overexpose and "pull".

 

Here I am going to fall on my sword and eat a huge bit of CROW on this forum and say that Capture One is very very good at this, and beats the crap outa Lightroom for this kind of thing. The Fill light slider in Lr is very good, but introduces noise. C1 has better noise handling so you can be more aggressive with the push move.

 

there I said it, C1 is better...caveat...the interface still sucks...and it is too expensive.

[chris_tribble]

In the old days we "shot for shadows" ... with the M8 I'm being really careful not to blow important highlights and am being rewarded with progressively better files at high ISO ...

 

re eating crow - I agree - and I also agree on C1 user interface and workflow ... So I'll stay with Lr and keep asking for better noise handling and sharpening for final output... I think they'll get there too!

[wparsonsgisnet]

Chris, I had to use the D2 in underexposure mode, sometimes, and then goose the files in PS. When I got the M8, I shot at an "expected" iso, in the same conditions. Given my observations, there was no need for me to underexpose the M8 shots. I have done some, but then just reshot.

 

I think that the pushed files are similar in noise structure (different cameras).

 

At 2500 -- in my case, with noise reduction -- I find the M8 totally satisfactory.

 

We know that Canon owns the hi iso noise prize, because of the full frame sensor. Leica more than makes up for that on 2 counts:

1. T-h-e L-e-n-s. That's why we're here, and

2. The best shadow detail I've seen from any image maker.

[eronald]

My Tuned1 profile is boosted in the shadows. You can underexpose by about -1/3 to about 1/2 stop if you are using it, or expose normally and use it to lift the shadows into view.

 

Edmund

[chris_tribble]

Edmund - your sterling efforts could almost pull me back to C1 ... Do I dive back in or stay with my oh so much more integrated Lr environment...? Ah decisions, decisions...

[wparsonsgisnet]

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I too am pleased with Edmund's profiles, exceedingly so.

 

I am also waiting for the dust to settle as far as automation is concerned. When the winner is announced, I'll move in that direction. Can PS possibly lose this race?

[Jamie Roberts]

Bill--

 

Automation of what, exactly?

 

PS isn't a RAW converter. ACR is, but to me it's lightweight for a pro workflow.

 

Lightroom is V1 software, so I refuse to comment, other than Adobe has a great track record with imaging, and RSP has a C1 heritage anyway

 

But C1 won't replace PS. To me they're completely complementary, even if PS is sometimes overkill for what I want.

 

Chris--

 

You will come back to C1! Really! Admitting it produces better results is just the first step

 

Ok--I'm just kidding. But when I think of the hours C1 saves me on each job, well, then it starts to look downright cheap!

[wparsonsgisnet]

Jamie, automation of workflow.

 

For example, in C1 at the moment, I'd like to

1. Apply a profile and wb to a set of pix -- I can do this now.

2. Do the cropping, then

3. Apply NR. For this I need an automation process.

 

For #3, if I use PS, I can use an automation workflow on a folder or on all the pix that are currently open. This may be how I end up doing this.

 

In the middle, I have a problem because I find BOTH C1 and PS lousy crop tools. I used to use Picture Window before I switched to PS to handle RAW. The crop tool there is much easier to use. In C1, it's hard to see the edge of the crop in a dark area. In PS, the center mark in the crop frame drives me nuts, because it keeps getting involved in the crop process. I would much rather be analysing negative space around the image and then fine tuning by getting the eyes where they make sense (usually top 1/3). This is really hard to do in both C1 and PS.

 

The day job keeps getting in the way, too.

 

When I start doing imaging full-time in a few years, I will need to be able to do this in a much more user-friendly fashion.

[eronald]

Jamie, automation of workflow.

 

For example, in C1 at the moment, I'd like to

1. Apply a profile and wb to a set of pix -- I can do this now.

2. Do the cropping, then

3. Apply NR. For this I need an automation process.

 

For #3, if I use PS, I can use an automation workflow on a folder or on all the pix that are currently open. This may be how I end up doing this.

.

 

With C1 Pro you just invoke a style that sets 1 and 3.

 

Edmund

[lars_bergquist]

In the old days we "shot for shadows" ... with the M8 I'm being really careful not to blow important highlights and am being rewarded with progressively better files at high ISO ...

---------------------

 

Those 'old days' were negative film only. There, you can increase the nominal exposure (which is a minimum exposure only) by a factor of eight and get good quality, though shadows as a rule stopped improving after 2—2.5 X, depending on the film. But underexposure was disastrous.

 

With reversal film however (and that included B&W reversal – remember them?) it was just the other way around. Here, the rule was to shoot for the highlights, preferably with an incident meter which of course nails diffuse highlights perfectly, and to let the shadows take care of themselves. Only light sources and specular highlights were permitted to go 'whiteout'. It is just the same with the M8. So we are actually back to dear old Kodachrome, which BTW M8 colour is tweaked to resemble! Many pros did routinely expose KC with a – 1/2 stop compensation, in order to get juicier highlights and higher saturation.

 

IMHO solid experience of quality B&W printing in a wet darkroom is not a bad ground for digital work.

 

The old man from the Age of Kodachrome I

[hankg]

With reversal film however (and that included B&W reversal – remember them?) it was just the other way around. Here, the rule was to shoot for the highlights, preferably with an incident meter which of course nails diffuse highlights perfectly, and to let the shadows take care of themselves. Only light sources and specular highlights were permitted to go 'whiteout'. It is just the same with the M8. So we are actually back to dear old Kodachrome, which BTW M8 colour is tweaked to resemble! Many pros did routinely expose KC with a – 1/2 stop compensation, in order to get juicier highlights and higher saturation.

This is how I shoot with the M8 as well. I don't "expose to the right". I'd rather be a 1/2 stop under and make sure I have all the highlight detail. The M8 files can take really big moves to pull out the shadows without getting posterization and artifacts. You would think the M8 files were 16bit they are so amenable to post-processing.

[hankg]

Here is an example of a situation with impossible dynamic range shooting right into the Miami sun. I exposed to hold the sky and let the shadows take care of themselves. The adjustments in post were quick and easy -a quick soft mask and some tone curve adjustments ( I boosted saturation as well for dramatic effect). If you have captured all the info with the M8 you will have a 'digital negative' with tremendous flexibilty in post.

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[hankg]

The full frame better shows the change. I was testing a 21/2.8 and had not quite got the DOF for the M8 quite right so focus is a little dicey.

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[Jamie Roberts]

Hank, I agree with you at low ISOs. In fact, when I have time, I'll actually take three shots with the M8 (highs, mids and lows) and merge the RAW output in PS.

 

But often I don't need to do that either. The camera has more flexibility than it should--something is strange in the math and the way the camera has been described. And I'm comparing to 1ds2, 5d and DMR.

 

When you get to higher ISOs though (like 1250) then you're back to shooting like a print. Pick what you want to blow out and expose for the shadows--to the right.

 

You're not going to pull detail out of the noise well enough otherwise.

[hankg]

Hank, I agree with you at low ISOs. In fact, when I have time, I'll actually take three shots with the M8 (highs, mids and lows) and merge the RAW output in PS.

 

But often I don't need to do that either. The camera has more flexibility than it should--something is strange in the math and the way the camera has been described. And I'm comparing to 1ds2, 5d and DMR.

 

When you get to higher ISOs though (like 1250) then you're back to shooting like a print. Pick what you want to blow out and expose for the shadows--to the right.

 

You're not going to pull detail out of the noise well enough otherwise.

That is a very useful bit of info. For me the M8 is an ISO 160-640 camera and 640 is pushing it. Which is not bad as at ISO 640 it beats the pants off of ISO 800 medium format color negative (which really should be exposed at 640). I find the M8 files better then my 1Ds files in many ways, their maleability in post being one.

[wparsonsgisnet]

With C1 Pro you just invoke a style that sets 1 and 3.

 

Edmund

 

Edmund, I'm looking at the Phase One site and it looks like I have to move up to PRO to do this. Is that right?

[Kimbo]

In my experience if you shoot RAW there is zero measurable difference between two files shot at the same shutter speed and aperture, regardless of the ISO selected. I assume the RAW file contains the actual sensor data pre any gain applied so changing ISO on the camera or changing exposure in the RAW convertor are equvalent. JPEG files processed by the camera may not be the same in each case. If this is right then digital ISO is just a convenience not a "real" adjustment.

[stunsworth]

I don't believe that's correct.

 

If you use the correct exposure for ISO 160, but set the camera to ISO 2500 and use the same aperture and shutter speed you'll be an almost totally blown out image, and no amount of applying negative exposure in the raw convertor will bring the highlights back.

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[sandymc]

ISO 1250 1/125 sec f/2 (correct exposure) with no adjustment of dng file versus ISO 640 1/125 sec f/2 (1 stop underexposed) with a +1 stop adjustment of dng file in Photoshop or Lightroom.

 

Short answer - the two images will be near identical, assuming you don't blow any highlights. Both are being shot at 1/125 sec f/2, so same number of photons hit the sensor, and same number of "noise" electrons get generated. "Near identical" rather than "identical" because you could get some amplification and clipping effects, but I'd doubt you'd ever notice those.

 

Sandy