Exposure Compensation or higher ISO??...

[chops]

I was just thinking about something today at work when someone was talking about setting the exposure compensation on their Canon EOS-1V so they could use 100 speed slide film for whatever they were shooting and still keep the tight grain instead of moving up to 200 speed film.

Now I was wondering.... with digital, if I were to shoot at ISO 200 when I really should be using ISO 400 or 800, could I just bump up the exposure compensation and keep the images noise free from the higher ISO like film, or does digital not work that way?

Hmmm.... watch'a think?! :?:

[davidwegs]

What the digital camera will do for EC is to change the shutter speed and/or the aperture to compensate for light not being there.

If you want tighter grain you will (with digital) simply be underexposing the image by 1 or 2 stops and hoping to post process it back up to normal. It can work but its not a great way to shoot in general.

[slin100]

You'll want to boost ISO first up to the camera's highest analog amplified ISO and then use negative EC from that point onwards. On a 10D, this is ISO 800. ISO 1600 actually uses ISO 800 but doubles the digitized data values coming out of the A/D converter. So, instead of using ISO 1600, you could use ISO 800 with EC -1. Do this with RAW only, not JPG. With JPG, you'll want to expose to the right to maximize the signal-to-noise ratio and keep important image data out of the dregs.

[chops]

You'll want to boost ISO first up to the camera's highest analog amplified ISO and then use negative EC from that point onwards. On a 10D, this is ISO 800. ISO 1600 actually uses ISO 800 but doubles the digitized data values coming out of the A/D converter. So, instead of using ISO 1600, you could use ISO 800 with EC -1. Do this with RAW only, not JPG. With JPG, you'll want to expose to the right to maximize the signal-to-noise ratio and keep important image data out of the dregs.
Hate to say it, but you kinda lost me on that one. :oops: Could you possibly run that by me again in laymen terms?

I'm trying to figure out why you would use a -1 EC. Doesn't that underexpose the image more? And why would you go (-)EC in RAW, but (+)EC in jpg?

And one more stupid question..... what is "dregs"?

Thanks! ;)

[tim]

I can answer one of those: dregs definition (http://dictionary.reference.com/search?q=dregs).

[chops]

I can answer one of those: dregs definition (http://dictionary.reference.com/search?q=dregs).
LOL.. Well I knew that at least. I thought that maybe he was refering to something strictly digital related.

[PacAce]

You'll want to boost ISO first up to the camera's highest analog amplified ISO and then use negative EC from that point onwards. On a 10D, this is ISO 800. ISO 1600 actually uses ISO 800 but doubles the digitized data values coming out of the A/D converter. So, instead of using ISO 1600, you could use ISO 800 with EC -1. Do this with RAW only, not JPG. With JPG, you'll want to expose to the right to maximize the signal-to-noise ratio and keep important image data out of the dregs.


Care to tell us what your source for your information is, because I'm inclined to disagree with a lot of what you said here, especially the last part about the RAW and the JPG.

[snibbetsj]

What the film camera guy is doing is under-exposing his slide film, i.e. making the camera think he has 200 speed film instead of 100 speed. This gives him higher shutter speeds with the same aperture. He has to tell the developer this so the developer will over-develop the film by 1 stop to get the correct images.

If you are shooting digital and are in Av or Tv mode (M won't care about EC) then you can set the exposure compensation for -X EC and under exposure your digital negative, you can then "over-expose" it in EVU, DPP, PS, or whatever you use.

[PacAce]

I was just thinking about something today at work when someone was talking about setting the exposure compensation on their Canon EOS-1V so they could use 100 speed slide film for whatever they were shooting and still keep the tight grain instead of moving up to 200 speed film.

Now I was wondering.... with digital, if I were to shoot at ISO 200 when I really should be using ISO 400 or 800, could I just bump up the exposure compensation and keep the images noise free from the higher ISO like film, or does digital not work that way?

Hmmm.... watch'a think?! :?:

The difference between film and digital is that film is made to be used at a particular ISO and the image quality and grain you get from it is optimized for that particular ISO. If you push a film to a higher ISO, image quality and grain will suffer. There is no such thing as a free lunch here. If there were, then everybody would be push processing a lower ISO film instead of using the higher ISO films.

Digital, however, is a different type of animal. The CCD or CMOS sensor is usually optimized for one ISO setting and that's usually the lowest ISO available. At this ISO setting, you get the best image quality with the minimum of noise. However, unlike film, you just can't pop in another sensor that is optimized for a higher ISO setting so that you can shoot in low light conditions. So, in order to be able to take pictures at lower light levels, you have to artificially boost the sensitivity of the sensor (i.e. increase the ISO). But changing the ISO of the sensor does not magically make it more sensitive to light like faster ISO films are. What you're basically doing when you increase digital ISO is causing the image data that is captures by the sensor to get amplified more to increase the signal level. However, you do not get this increase in signal level for free. When you amplify the image signal, you are also amplifying the noise signal that's inherent in the sensor and accompanying circuitry. Of course there are noise cancellation circuitry built into the electronics to minimize the noise but noise still isn't eliminated 100%.

So, the point I'm trying to make here is that the hardware of a digital camera optimizes the image quality you get out of the camera no matter what ISO you are using. I doubt one can get a better image out of a camera by pushing the digital image (i.e. using a low ISO setting, under exposing the image by using negative EC, and then increasing exposure during post processing and then trying to deal with the noise in the image that's inherent in under exposed images).

[snibbetsj]

Perhaps another way to explain relates to music. If you record a song to a high quality tape through a very good recorder with a high signal-to-noise ratio it will have little noise, however, if you record the same music to the same tape with a recorder with a lower signal-to-noise ratio, it will be noticable (compared to the other tape). When you up the ISO on a digital camera, you're effectively lowering the S/N ratio of the recording medium)

Jeff

[slin100]

Care to tell us what your source for your information is, because I'm inclined to disagree with a lot of what you said here, especially the last part about the RAW and the JPG.
Sure. UseNet. http://groups-beta.google.com/group/rec.photo.digital/browse_thread/thread/8d96a3aab7603342/c3bdeb86d8a09f73?q=john+sheehy+group:rec.photo.dig ital+10d+iso+1600&_done=%2Fgroups%3Fhl%3Den%26q%3Djohn+sheehy+group: rec.photo.digital+10d+iso+1600%26qt_s%3DSearch+Gro ups%26&_doneTitle=Back+to+Search&&d#c3bdeb86d8a09f73 :eek:

Before you go discounting the claim, read John Sheehy's post. John Sheehy is a pretty sharp guy. I see no reason for him to and no indication that he has lied or drawn the wrong conclusions. I believe he verified his findings by directly examining the RAW data using DCRAW, an open-source RAW decoder. In another post of his, he claims that the values in an ISO 1600 RAW file were all even, confirming his hypothesis that the A/D output was doubled.

Now, can you tell me why you disagree with me?

[slin100]

So, the point I'm trying to make here is that the hardware of a digital camera optimizes the image quality you get out of the camera no matter what ISO you are using. I doubt one can get a better image out of a camera by pushing the digital image (i.e. using a low ISO setting, under exposing the image by using negative EC, and then increasing exposure during post processing and then trying to deal with the noise in the image that's inherent in under exposed images).
If you accept what John Sheehy asserts, that there is a point at which the amount of analog signal amplification is maxed out and that any further ISO increases are achieved in the digital domain, then it's possible to achieve a better image by pushing the digital image.

The digital domain manipulation is analagous to the digital zoom feature on P&S cameras. With digital zoom, it's not real zooming like optical zoom, but faked by cropping the image and resampling. Similarly, the high ISOs are achieved by a similar form of manipulation. When we all found out about digital zoom how quickly did we stop using it?

[PacAce]

Sure. UseNet. http://groups-beta.google.com/group/rec.photo.digital/browse_thread/thread/8d96a3aab7603342/c3bdeb86d8a09f73?q=john+sheehy+group:rec.photo.dig ital+10d+iso+1600&_done=%2Fgroups%3Fhl%3Den%26q%3Djohn+sheehy+group: rec.photo.digital+10d+iso+1600%26qt_s%3DSearch+Gro ups%26&_doneTitle=Back+to+Search&&d#c3bdeb86d8a09f73 :eek:

Before you go discounting the claim, read John Sheehy's post. John Sheehy is a pretty sharp guy. I see no reason for him to and no indication that he has lied or drawn the wrong conclusions. I believe he verified his findings by directly examining the RAW data using DCRAW, an open-source RAW decoder. In another post of his, he claims that the values in an ISO 1600 RAW file were all even, confirming his hypothesis that the A/D output was doubled.

Now, can you tell me why you disagree with me?

I'm not discounting the claim by any means. I can't because I'm not an expert on the subject matter nor am I privy to Canons proprietary info on how they work the ISO stuff. What I did say is that I'm inclined to disagree with what you said. That's the reason I was asking for your source, so that I can check it out myself. After reading your "source", I have not changed my views the least bit. I'm still inclined to disagree with what was noted by Mr. Sheehy in your reference. But I am going to keep an open mind until I can research this further.

Mentioned was made of reaching the limit of the analog amplification gain at ISO 800 and resorting to digital gain to get ISO 1600 and 3200 images. So, the recommendation is to shoot at ISO 800 and then underexpose by 1 stop to get the ISO 1600 equivalent or 2 stops for ISO 3200 because letting the camera do it is not good if digital amplication is being used. Well, did it not occur to you that shooting at ISO 800 and then overexposing during post processing is doing exactly that, increasing the image gain by digital amplifcation even though you may not think of it in that light when you are using Photoshop. THe the truth of the matter is, anything you do with Photoshop is digital manipulation. So, again, my take on the whole matter is that a hardware that was designed specifically to handle a certain function (in this case the camera shooting in ISO 1600 or ISO 3200) can do a better job at it than one trying to perform the same task adhoc with Photoshop or any other photo editing program.

Now, regarding the "shooting to the right" with RAW vs. JPEG. Why would you say that you should shoot to the right with JPEG but not with RAW. WIth RAW, you are essentially saying that you should shoot to the left by using -EC. Or did I misunderstand your statement?

[chops]

Boy oh boy, this is all getting more and more confusing. LOL :p

Actually, I am beginning to understand some of it, but still have a lot to learn.

And yes, I am still wondering about that RAW vs JPG, left and right thing.

[slin100]

I'm not discounting the claim by any means.... What I did say is that I'm inclined to disagree with what you said.
That's fair.


...Well, did it not occur to you that shooting at ISO 800 and then overexposing during post processing is doing exactly that, increasing the image gain by digital amplifcation even though you may not think of it in that light when you are using Photoshop. THe the truth of the matter is, anything you do with Photoshop is digital manipulation. So, again, my take on the whole matter is that a hardware that was designed specifically to handle a certain function (in this case the camera shooting in ISO 1600 or ISO 3200) can do a better job at it than one trying to perform the same task adhoc with Photoshop or any other photo editing program.

Yes, it did occur to me. If you accept the notion that in-camera digital amplification is analagous to in-camera digital zooming, then you should agree that doing it in Photoshop is not worse. We all know that in-camera digital zooming can be achieved in postprocessing by interpolation in Photoshop. Similarly, Photoshop can digitally amplify image data as easily as the number and with a lot more flexibility. With the camera you only have, at best, 1/3 stop increments with which to manipulate the data. Finally, digitally pushing the image in Photoshop is better because you have an extra stop of headroom for highlights. From John Sheehy:
You actually get better image potential with the 10D by shooting ISO 800 at -1EC than shooting ISO 1600 with no compensation, as you get a stop more of highlight headroom, and the part of the dynamic range they both capture (all but the extra stop) is of exactly the same quality, noise- and posterization-wise.


Now, regarding the "shooting to the right" with RAW vs. JPEG. Why would you say that you should shoot to the right with JPEG but not with RAW. WIth RAW, you are essentially saying that you should shoot to the left by using -EC. Or did I misunderstand your statement?
I'm not really advocating shooting to the left with RAW. You should still shoot to the right as far as possible but if you need to bump the ISO and you're already at ISO 800, use negative EC instead.

As to why this doesn't work as well with JPG, gamma encoding changes the rules of the game a bit. I haven't fully thought this out to explain it coherently. Furthermore, the kids are awake and I have to serve up breakfast! :lol:

[spearce6]

The advice in this thread is very confusing.

The answer to the question is not.

Yes, you can do this with digital. Just shoot in RAW, use a large aperture and underexpose one to two stops to get the fastest shutter speed with the available light.

Take the RAW file and bring it back to life on your PC.

I have heard comments like a well exposed image is better and yes, it probably is. But if you are somewhere without a tripod and the shutter speed is too low at ISO 100, your choices are limited. This technique gives better results than upping the ISO to maximum.

See my full article and example images here:

http://www.steve-pearce-photography.com/10dlowlighttechnique/

[J.A.F. Doorhof]

Hi,
You can also look at it from the digital domain.
A properly exposed picture will have values from 0 (black) to 254 (peak white)
This is your dynamic range or contrast ratio.

When you underexpose you will loose resolution in the top end, meaning the picture will look very dull, when you shoot the right something else happens, by extending the black down with curves you can get a more dynamic looking picture because somehow the human brain will forgive lack in black detail better than lack in white/middle gray detail.

By getting a higer ISO and proparly exposing with the modern machines the noise is acceptable, much better in my opinion than for example underexposing a 800ISO shot.

Greetings,
Frank

[alan sh]

ref:

"Well, did it not occur to you that shooting at ISO 800 and then overexposing during post processing is doing exactly that, increasing the image gain by digital amplifcation even though you may not think of it in that light when you are using Photoshop"

My thoughts are that PS CS will do the post processing better than digital amplification because there is no electronic noise component involved - i.e. its a much cleaner image afterwards. Am I wrong ?

Alan

[Jon]

Sure. UseNet. http://groups-beta.google.com/group/rec.photo.digital/browse_thread/thread/8d96a3aab7603342/c3bdeb86d8a09f73?q=john+sheehy+group:rec.photo.dig ital+10d+iso+1600&_done=%2Fgroups%3Fhl%3Den%26q%3Djohn+sheehy+group: rec.photo.digital+10d+iso+1600%26qt_s%3DSearch+Gro ups%26&_doneTitle=Back+to+Search&&d#c3bdeb86d8a09f73 :eek:

Before you go discounting the claim, read John Sheehy's post. John Sheehy is a pretty sharp guy. I see no reason for him to and no indication that he has lied or drawn the wrong conclusions. I believe he verified his findings by directly examining the RAW data using DCRAW, an open-source RAW decoder. In another post of his, he claims that the values in an ISO 1600 RAW file were all even, confirming his hypothesis that the A/D output was doubled.

Now, can you tell me why you disagree with me?
Well, he seems to contradict himself in his description of what happens.

10D doesn't really have ISO 3200. The 10D uses amplifier gain to get ISOs 100 through 800. ISO 1600 is ISO 800 under-exposed by one stop internally in the camera, and pushed to 1600 by doubling the RAW data.
ISO 3200 works the same way; the gain of the amplifier is set for ISO
1600, but the exposure is done at -1 EC and pushed by doubling the RAW
data, also.
Rephrased, he appears to be saying that:

At ISO 100-800 the signal's run through a linear amp.
At ISO 1600, the 1-stop underexposed signal's run through a linear amp at the ISO 800 setting and then doubled
At ISO 3200, the 1-stop underexposed signal's run through a linear amp at the ISO 1600 setting and then doubled.
So, to get ISO 1600, the signal's amplified to ISO 800, then doubled, but to get ISO 3200, the signal's amplified to 1600, then doubled. In which case, why not get ISO 1600 by amplifying the signal to ISO 1600 rather than to ISO 800 x 2? And if it operates the way he says, isn't ISO 200 a 1-stop underexposure of ISO 100, run through a linear amp at a gain of +2, ISO 400 a 2-stop underexposure of ISO 100 run through a linear amp at gain of +4, and so on? What's different about 1600 or 3200? He's making a distinction without a difference. A 5-stop (ISO 100-ISO 3200) speed jump is a 32X signal boost (amplification or gain), and at that level of amplification you will definitely see loss of precision in the output values. This could very well be what he's seeing and reporting on.

[slin100]

Well, he seems to contradict himself in his description of what happens.


Rephrased, he appears to be saying that:

At ISO 100-800 the signal's run through a linear amp.
At ISO 1600, the 1-stop underexposed signal's run through a linear amp at the ISO 800 setting and then doubled
At ISO 3200, the 1-stop underexposed signal's run through a linear amp at the ISO 1600 setting and then doubled.

You bring up a good, valid point. I believe your interpretation is correct and mine is wrong. I found another posting from John that backs up your interpretation.
So, to get ISO 1600, the signal's amplified to ISO 800, then doubled, but to get ISO 3200, the signal's amplified to 1600, then doubled. In which case, why not get ISO 1600 by amplifying the signal to ISO 1600 rather than to ISO 800 x 2?
I don't know. Perhaps the amp starts to behave non-linearly when pushed all the way to ISO 1600. Unfortunately, I have no evidence to back this conjecture. That might explain why ISO 3200 needs to be enabled.
And if it operates the way he says, isn't ISO 200 a 1-stop underexposure of ISO 100, run through a linear amp at a gain of +2, ISO 400 a 2-stop underexposure of ISO 100 run through a linear amp at gain of +4, and so on? What's different about 1600 or 3200? He's making a distinction without a difference.He did make a distinction. The difference is where the gain is being applied: in the analog stage or the digital stage. His point is that it's mostly analog, but that there's 1 stop of digital amplification going on at ISO 1600 and ISO 3200.
A 5-stop (ISO 100-ISO 3200) speed jump is a 32X signal boost (amplification or gain), and at that level of amplification you will definitely see loss of precision in the output values. This could very well be what he's seeing and reporting on.Yes, he says that ISO 1600 and ISO 3200 RAW data values are only even, which corresponds to a 1-bit loss of precision.

[slin100]

See my full article and example images here:

http://www.steve-pearce-photography.com/10dlowlighttechnique/
Steve,

I looked at your article. Your advice is similar to mine except that you recommend to start using negative EC at lower ISOs, even ISO 100 with EC -1 instead of ISO 200.

It's difficult to draw conclusions from your images. You don't provide 100% crops of the same image for both the ISO 400 with EC -2 shot and the ISO 1600 shot. The ISO 400 crop is from a dim portion of the image but the ISO 1600 shot is of the bright, central part of the dome. It's much harder to perceive noise in dim areas than bright areas.

In my experience, the noise from the 10D is quite low up to ISO 400. I believe that resorting to negative EC below that ISO is not necessary.

[Jon]

But how does the hypothetical "digital stage" differ from a two-stage linear amp dealing with analog data inputs all the way? And if 1600 off the linear amp is showing some problems, why use it rather than 800 quadrupled? Conversely, why not use the 1600 off the linear amp instead of 800 doubled for your 1600 value if the 1600 value's good enough to use as the basis for 3200 calculations?

[mackb]

Furthermore, the kids are awake and I have to serve up breakfast! :lol:


lol.......thanks for some comic relief

[spearce6]

It's difficult to draw conclusions from your images. You don't provide 100% crops of the same image for both the ISO 400 with EC -2 shot and the ISO 1600 shot. The ISO 400 crop is from a dim portion of the image but the ISO 1600 shot is of the bright, central part of the dome. It's much harder to perceive noise in dim areas than bright areas.

In my experience, the noise from the 10D is quite low up to ISO 400. I believe that resorting to negative EC below that ISO is not necessary.

Slin,

Maybe my article is a little unclear, sorry.
Both the dome 100% images are at ISO400, underexposed two stops and then taken back from RAW in C1.

Only the last two images on the page are at ISO1600.

The 10D noise is low up to 400 I agree, but often 400 is not even enough to get a handheld shutter speed - thus in the Basilica I used ISO400 with -2 stops to give an effective 1600. The last two images in the article show a comparison of a shot at ISO 1600 so that you can see the merits of 400 -2 stops.

I don't suggest resorting to negative EC below ISO400 - I have shown a table of shutter speeds and ISO's for comparison, but there is no reason not to take a negative EC shot with a low ISO. I have not made comparison images of noise at say ISO200-1 vs ISO400-2, but there is no reason not to try. There might be a slight benefit.

I don't agree that it's much harder to perceive noise in dim areas - quite the opposite. I think noise is always more noticable in dark areas of images.

[slin100]

But how does the hypothetical "digital stage" differ from a two-stage linear amp dealing with analog data inputs all the way? And if 1600 off the linear amp is showing some problems, why use it rather than 800 quadrupled?The difference is that a digital multiplier stage magnifies the quantization error produced by the A/D converter. If the error coming out of the A/D is x, then doubling the values will increase the error to 2x. Quadrupling the quantization error will probably exhibit quite noticeable posterization effects.
Conversely, why not use the 1600 off the linear amp instead of 800 doubled for your 1600 value if the 1600 value's good enough to use as the basis for 3200 calculations?That I cannot answer because I don't know what went through the designer's minds. That ISO 3200 is normally unavailable unless ISO Expansion is enabled in the Menu suggests the possibility that the designers may have felt uncomfortable with using a linearly amplified 1600.

[slin100]

The 10D noise is low up to 400 I agree, but often 400 is not even enough to get a handheld shutter speed - thus in the Basilica I used ISO400 with -2 stops to give an effective 1600.Did you consciously choose ISO 400 with EC -2. Why not ISO 800 with EC -1? In your experience does the former exhibit lower noise?
The last two images in the article show a comparison of a shot at ISO 1600 so that you can see the merits of 400 -2 stops.
In the audio world, it's quite important to match the sound levels when doing A-B comparisons. Some say that even a 1/2 decibel difference in volume can tilt the balance in favor of the louder system. Similarly, it's important to match the exposure levels between two digital images to provide a fair comparison. It's virtually impossible, IMO, to draw any conclusions from your examples because the exposure levels are different and the two images are different, as well! Of course, I can see the noise in the ISO 1600 100% but without an identical crop at ISO 400 with EC -2, well ...

You have demonstrated, OTOH, what can be achieved by aggressively pushing ISO in the digital domain.

I don't agree that it's much harder to perceive noise in dim areas - quite the opposite. I think noise is always more noticable in dark areas of images.
I think I didn't articulate myself well. I meant to say that it's easier to perceive noise in the dark areas when the levels are brought up to accentuate the differences.

[PacAce]

This evening I conducted a little test of my own. I made two test exposures. One was shot at ISO 400 with -2 EC and then converted to TIFF with +2 exposure increase. The other was made at ISO 1600 with 0 EC. The conversion was done (using EVU) "as shot" except for the +2 stop exposure increase for the ISO 400 shot to compensate for the -2 EC. Also, I adjusted the WB on both to correct WB. The shots were then loaded into PS so that I could resize them and make the 100% crop images. No editing or sharpening was done in PS.

Here are the EXIF info from the two shots:


Shooting Mode
Aperture-Priority AE
Tv(Shutter Speed)
1/6
Av(Aperture Value)
5.6
Metering Mode
Evaluative Metering
Exposure Compensation
-2
ISO Speed
400
Lens
28.0 - 135.0mm
Focal Length
122.0mm
Image Size
3072x2048
Image Quality
RAW


Shooting Mode
Aperture-Priority AE
Tv(Shutter Speed)
1/6
Av(Aperture Value)
5.6
Metering Mode
Evaluative Metering
Exposure Compensation
0
ISO Speed
1600
Lens
28.0 - 135.0mm
Focal Length
122.0mm
Image Size
3072x2048
Image Quality
RAW


These are the resized images of the two test shots:

http://tanseikai.com/pacace/images/ISO-A1.jpg

http://tanseikai.com/pacace/images/ISO-B1.jpg


And these are 100% crops from the same test shots. So, which is which? Can anybody tell? Or maybe make a guess? I'll give you a hint.

http://tanseikai.com/pacace/images/ISO-A2.jpg

http://tanseikai.com/pacace/images/ISO-B2.jpg


http://tanseikai.com/pacace/images/ISO-A3.jpg

http://tanseikai.com/pacace/images/ISO-B3.jpg

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The 1st picture in each set was shot at ISO 1600. The 2nd picture was shot at ISO 400 and pushed to ISO 1600. As far as I'm concerned, why would I want to bother with the hassle of pushing ISO when the real ISO setting yields equal or even better results than using pushed ISO. :)

[chops]

Nice PacAce!! I do notice that the ISO400 pushed image tends to be a tad bit on the cool side as well. When being pushed, the noise seems to be blue, where the noise at ISO1600 seems to be a little green.BTW, which body did you shoot that with?... the 10D or 20D? The only reason I ask is because those images of yours seem to be a heck of a lot cleaner than mine at ISO 1600.

[PacAce]

Nice PacAce!! I do notice that the ISO400 pushed image tends to be a tad bit on the cool side as well. When being pushed, the noise seems to be blue, where the noise at ISO1600 seems to be a little green.BTW, which body did you shoot that with?... the 10D or 20D? The only reason I ask is because those images of yours seem to be a heck of a lot cleaner than mine at ISO 1600.

I wouldn't put too much stock in the overall color cast of the images since the WB correction may not have been exactly the same for both images. I tried to get them as close as possible but doing that manually is a little tough. However, you are correct in your assumption that there will be a slight color shift when you adjust the exposure by a stop or more.

I used the 10D for my test since that was the camera being discussed, if I recall correctly.

[PacAce]

The only reason I ask is because those images of yours seem to be a heck of a lot cleaner than mine at ISO 1600.

What I have learned about the high ISO settings, on the 10D at least, is that if you correctly expose the images, you will get the minimum of noise generated. Also, the darker areas such as shadows will show more noise than the brighter areas in the highlights. This is the reason shooting to the right of the histogram without blowing the highlights is so much endorsed. Comparing two images shot at, say, ISO 1600, the darker of the two will reveal more apparent noise than the other.

[slin100]

PacAce,

I think you certainly confirmed that it makes sense to bump ISO first. ISO 1600 looks better than ISO 400 with EC -2. It would have been interesting to have seen the same shot at ISO 800 with EC -1. I did a quick test last night at ISO 1600 and ISO 800 with EC -1 and the noise levels looked comparable to me.