Getting the most out of ACR - try this

Started Jun 19, 2006 | Discussions
Benedict Slotte Senior Member • Posts: 1,165
Getting the most out of ACR - try this

My search for ever better RAW conversion quality (and workflow) has lead me to some very effective tweaks that you can use to get rid of a couple of ACR's typical problems.

1. Colours (these tweaks are specific to 5D):

This is what most people complain about in ACR. Basically, as can be seen in all threads describing this, one has to quite considerably alter the Red hue and Red saturation slider on the Calibration page in ACR. Red Hue has to be decreased to -10...-15, Red saturation has to be boosted to +20...+25. Some minor adjustments should also be made to the other sliders, but in my own calibration trials the ideal values for these have still stayed within about -5 to +5. I have used a Gretag Macbeth chart and the ACR calibrator script (the improved one that optimizes all patches instead of just red, green and blue) to get these values.

More specifically:
Red hue = -12
Red saturation = +24
Green hue = -7
Green saturation = +1
Blue hue = 0
Blue saturation = -5

2. Dynamic range and saturation (these settings are good for my 5D but probably apply pretty well to all 1D series cameras too):

Using the default or automatic values for ACR doesn't produce a good result in my opinion. Setting things to zero or center or such seemingly "reasonable" values often produces too much blown-out highlights. After much experimenting and some calibration (mainy, trying to get things evenly spread out around the midtone defined through spot metering) I found that the best way to get a good dynamic range and good colours is to pull down the Exposure slider a lot, push up the Brightness slider a lot, decrease contrast, and increase saturation. Also the Curve settings have to be altered. Automatic settings in ACR do some of these things too, but not always well. More specifically:

Exposure = -2.5
Shadows = 0 (may be increased at will - see below)
Brightness = 150 (!)
Contrast = -25 (can be increased if needed)
Saturation = +25 (may have to be decreased if Contrast is increased)

Curve = Linear

Since Brightness is now at its maximum, it can no longer be boosted if the need arises. Further adjustment should therefore be done using Curve by adding and dragging points around. Shadows can be darkened by the Shadows slider - BUT the bad thing is that often when you do this, ACR has a tendency to exaggerate shadow noise and also in general to make the shadows ugly-looking. This brings us to...

3. Noise reduction:

The default values on the Detail page are, let me say it again, not good. Too much Sharpness creates strong halos around contrasty borders. I use no more than 5, and sometimes 10 (the default value 25 is way too high, for a 5D at least).

Too much Color noise reduction makes small areas of saturated colours appear washed-out. A good example is a shot of a crowd of people, whose lips become totally pale if you use too high values here.

My default is 2, and occasionally I go up to 5, and only in extreme cases (when the above-mentioned artifact isn't visible) I go above 10. Again, the default value 25 is often way too high. Perhaps this might be part of the reason why some people claim (quite correctly!) that ACR produces washed-out colours using default values for 5D.

More specifically, I have found the following to be a best compromise:
Sharpness = 5 (can be increased to 10 sometimes)
Luminance smoothing = 5

Color noise reduction = 2 (can be increased in high ISO shots, but watch the "pale lips" artifact)

Furthermore, to combat the ugly-looking shadows of ACR, I have found that it's best to alter the Linear curve (see above) so that it tapers smoothly to a value that is NOT ZERO at the left end. You may think that this causes washed-out shadows, but the effect is very minor if done well, and it beats having grainy and ugly-looking shadows. Shadows aren't usually completely black anyway, because there is always a little noise. My current default Curve has the following 4 points (given as (x,y)):

(0,4)
(13,8)
(36,30)
(255,255)

I find that this approach gets rid of the annoying graininess of the shadows often produced by ACR. Now one can darken shadows using the Shadows slider without too much artifacts.

Try these tweaks and see if you like them. I tried, and after about one month with C1 I went back to ACR and will not look back. The speed and lens correction features of ACR also helped the decision. For best results, make your own calibration in step 1 above.

Note that all these settings apply to ACR 3.3.

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B. Slotte
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rameshpkumar Senior Member • Posts: 1,664
Re: Getting the most out of ACR - try this

Great!
I am going to try this tonight and I will report my findings.
--
Thanks
Ramesh
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james b norman Senior Member • Posts: 2,150
Re: Getting the most out of ACR - try this

hmmm - you are suggesting decreasing exposure by 2.5 stops? seems like that will significantly increase shadow noise, yes?
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Gary Jean Senior Member • Posts: 2,533
Have you read "Real World ACR"...

...by Bruce Fraser?

Your calibration settings are interesting, but your exposure and brightness moves are extreme.
--
Gary

PhotoGearJunkie Regular Member • Posts: 212
Thanks for the info! Where's the...

Where is the ACR calibrator script that you mentioned in step 1, above?

And again, thanks for all of this info!

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OP Benedict Slotte Senior Member • Posts: 1,165
Re: Have you read "Real World ACR"...

No, haven't read that book but I should have a look. I do have two other books that describe ACR to some extent though.

Yes, this is indeed extreme. I wanted the maximum dynamic range but still good colours. If you read the 5D review here on dpreview you can see that they used somewhat similar settings there in their RAW dynamic range test, albeit less extreme. I pushed this further and corrected the midtones... anyway, in most cases this looks good, try it! (Occasionally you will want to slightly increase contrast and shadow darkness, and lower or raise saturation, though. If your scene has low contrast to begin with, such as a winter landscape on a cloudy and foggy day, this dynamic range might be too extreme, but pushing up the contrast slider will do most of the trick.)

I must admit that I have used these "new" settings for only a few days so far, but I tried to process some old RAWs and they were OK. If I come up with even better values later I might also post them here.

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OP Benedict Slotte Senior Member • Posts: 1,165
Re: Getting the most out of ACR - try this

No it won't. Negative exposure compensation in ACR itself isn't the same as when done in the camera. In the latter case noise WILL increase as we both know - but ACR does this mathematically on the pixel values and there is no increase in noise (except maybe for extremely minor rounding errors).

Oh by the way, maybe it wasn't perfectly clear in my post that Exposure = -2.5 meant the exposure slider in ACR, not the camera...

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OP Benedict Slotte Senior Member • Posts: 1,165
Re: Thanks for the info! Where's the...

The calibrator is described here:

http://forums.dpreview.com/forums/read.asp?forum=1032&message=17243762

But you do need to get yourself a Color Checker chart first if you don't have one.

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krusadr Senior Member • Posts: 2,988
Benedict

It looks to me like your monitor is in serious need of calibration.

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rameshpkumar Senior Member • Posts: 1,664
It will be nice if you can post some samples

May be some daylight shots with blue sky and green vegetation.
Some night shots and indoor shots will be nice too.
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OP Benedict Slotte Senior Member • Posts: 1,165
Re: Benedict

krusadr wrote:

It looks to me like your monitor is in serious need of calibration.

Why? It IS calibrated. If the colours look bad on your screen this way, then your camera renders colours differently. There are some individual variations as far as I know.

Do you mean the colours look over/undersaturated or are just biased towards red/blue/cyan/whatever? If you mean the latter, you just have to make your own ACR calibration and use those settings on the Calibrate tab instead of my settings.

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Bobo Hodls
Bobo Hodls Forum Pro • Posts: 40,127
Interesting

I don't agree with all of the assessments, but I appreciate the detail and scope of your findiings. Particularly, the red saturation issue is spot on (though I will be loading your suggestions as a developing option to check them out). I don't agree about the exposure settings, and it all depends on the subject and what one had to cope with. I like to start out with everything flat anyway, to see how much leeway there is to play with.

Mainly, this is a thanks for sharing your findings.

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You'll have to ignore the gallery's collection of bad compositions, improper exposures, and amateurish post processing.

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Chief Senior Member • Posts: 1,531
tag to see samples (nt)

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gium Senior Member • Posts: 1,641
Re: Getting the most out of ACR - try this

Thanks for the effort.. but my skintones are just incredibly red after I made the changes and boosted up the red saturation. That's no good at all. I'm using a calibrated CRT monitor btw (Spyder 2). Perhaps the reds look good on landscapes, but for skintones they sure don't.

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rameshpkumar Senior Member • Posts: 1,664
Re: Getting the most out of ACR - try this

Even though I have not tried these setting, I am a bit suspicious about boosting red. Most of the time I find that 5d is blowing red and I do not see this problem with other colors. So my work flow has 10% more saturation for blue and green and red stays where it is.
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gium Senior Member • Posts: 1,641
Re: Getting the most out of ACR - try this

I was also surprised about the boosting of the red. The 5D (also an issue with the 20D) is known to blow red, that's one of the most common known things, so I don't understand why boosting red like that will result in better color balance.

Perhaps it works for landscapes, but in the case of skintones (where Nikon users keep reminding us that our skintones are too red ), boosting red even more is really strange.

rameshpkumar wrote:

Even though I have not tried these setting, I am a bit suspicious
about boosting red. Most of the time I find that 5d is blowing red
and I do not see this problem with other colors. So my work flow
has 10% more saturation for blue and green and red stays where it
is.
--
Thanks
Ramesh
My gallery: http://www.world-of-photos.com

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andrewD2
andrewD2 Veteran Member • Posts: 9,493
Re: Getting the most out of ACR - try this

Generally the saturation should not have to be boosted to get a natural looking image. Before looking to fixing saturation the contrast should be correct. You are lowering the contrast and then boosting the saturation.

Andrew

Bobo Hodls
Bobo Hodls Forum Pro • Posts: 40,127
Re: Interesting

Well, the only thing I've adopted is to put the Red saturation a bit lower. I can see it only being necessary when the are bright reds in a scene (not very often in my images).

The rest of the advice really doesn't work out. But I'll let you fathom why by getting Frasier's book on ACR.

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OP Benedict Slotte Senior Member • Posts: 1,165
Samples & further comments

Samples can be found here:

http://bslotte.smugmug.com/share/hdZCWx7F5YxfM

Thanks for all your comments. I'll address some of them one by one:

1. The reds.

While it's true that 5D oversaturates the reds when shooting JPG, the opposite is actually true for RAW and ACR. Both my eyes and my calibrator tell me this. I have used C1 with Magne's profiles (high saturation) as a reference also, and using my above-mentioned Calibration page settings I get a much closer match.

If some of you don't get better 5D colours this way, it's probably partly because of individual differences between cameras. Judging by the different settings shown on other similar threads, it seems the variations can be pretty big.

Note also that my monitor didn't influence this calibration - it was totally out of the loop. The script matched actual numerical colour values in the RAW file to the corresponding target values for the Gretag Macbeth chart, so no influence from the monitor. And my monitor is well-calibrated (average dE is between 1 and 2).

2. Exposure, brightness etc. settings.

While it may seem crazy to use such extreme values, this is actually in line with what was found in the 5D review. See

http://www.dpreview.com/reviews/canoneos5d/page23.asp

Values found there are along the same line as my values, although less extreme. Naturally, I also don't have to use such extreme values always, but I have a couple of other less extreme default settings to choose from for lower-dynamic-range shots. And I don't use these settings as such, but only as a starting point for further tuning. However, using these settings I find I can get more quickly to the goal than using ACR's default settings or any "zero/neutral" ACR settings.

When I started out with ACR I felt uncomfortable about moving the Exposure slider too far away from zero. After all, if the shot is properly exposed, you would think that further exposure compensation can only be unnecessary. But gradually I found out that quite a lot of negative Exposure coupled with quite a lot of Brightness increase could extract more dynamic range and give a more pleasant tonal response. Also, reducing Contrast increases dynamic range, but at the expense of saturation (which is kind of annoyng in ACR), so therefore the Saturation slider has to be pushed up also. This is how I arrived at the settings I described earlier.

Naturally, all people have slightly different habits of exposing (some expose more to the right than others), so my settings will not work for everyone.

3. Noise reduction by altering the Curve.

Check my sample using the link above. The difference should be pretty huge if your monitor is good at showing low tonal values. I have found also that sometimes you have to move the Shadow tint slider just slightly away from zero (e.g. -2, -1, +1, +2) to further reduce shadow graininess in black or nearly black areas.

My point is that by making the Curve taper to a non-zero value the way I described, you can reduce the contrast in the extreme shadows to the point that you get much less noise. If you taper it to zero it quite often looks worse for some reason. I think this might be because then the negative "peaks" of the shadow noise get clipped, making a more grainy impression. (Remember that noise is a signal that contains both positive and negative values.) Of course there is no magic Curve that works in all cases, but the general idea works in most cases by moving those points around a little bit. The noise reduction slider does the rest.

4. The "pale lips" artifact.

Again, see my samples above. Those are 100% crops of the mouth of a guy on one of my quite recent photographs. The white balance is a bit off since I didn't adjust it for this sample, but you get the idea about what too high colour noise reduction values do in ACR. (Noise reduction in C1 has the same effect by the way, but to a lesser extent.)

I will investigate these settings further and get back if I find something that works even better. Some day I plan to get an optical densitometry calibration strip to further tune the dynamic range and tonal response.

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astefot Senior Member • Posts: 2,889
Strange samples...

http://bslotte.smugmug.com/share/hdZCWx7F5YxfM

These are very strange samples - most of them have extreme scene contrast; generally speaking, these are not ideal targets to "calibrate" ACR. I think the rather extreme examples you chose are responsible for the rather extreme settings you recommend.

The only point I can really relate to is the sharpness setting: I agree that with the 5D, the ACR default setting is much too aggressive, especially when further processing the picture in PS. I have changed the default sharpness value to 15, many times, I lower it to zero. Regarding colors, I tweak until the colors "look and feel" right - that's the big advantage of ACR, it allows you to work with colors in a creative way. I use a customized curve with is close to the predefined trong/heavy contrast curve; this nicely simulates the shoulder and toe characteristics of film, the resulting picutres have much more "snap".

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