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Photoshop ACR and Exposures

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  #1  
Old 01-12-2015, 12:16 PM
Rex Rex is offline
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Photoshop ACR and Exposures

What ho,

Not sure if this is the correct dept, but will plough ahead anyway! I am more than happy to be behind the curve with a PC running XP / 3gb RAM and CS3.

I make exposures with my Nikon D300, in manual, bracketing five exposures, 2/3 stop +/- each side of the manual metered setting. This way, I have covered all my bases for wither luminosity blending or HDR. I usually check the histogram to ensure that the middle exposure is not overexposed.

When I open the images in ACR, I have the Landscape Camera Profile selected because it gives vibrant colours.

But here is the thing; on opening the best exposure (usually the middle one) in ACR, it usually appears as well underexposed and needs at least +1.5 on the exposure slider to return it to normal. Usually, the highlights are well to the right of the highlight end of the histogram.

It is not a particular problem since RAW has enough to correct the image, but I don't understand why.

Or to put it another way, my normal camera exposure with a good camera histogram, looks underexposed in ACR.

Am I doing something wrong?

Thanks and toodle pip!
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Old 01-12-2015, 01:49 PM
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andrewrodney andrewrodney is offline
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Re: Photoshop ACR and Exposures

Optimal exposure for the raw data isn't anything like optimal exposure for the JPEG:

http://www.digitalphotopro.com/techn...g-for-raw.html

You should bracket, play around normalizing the Exposure slider as illustrated above, then you know the optimal exposure for the raw without blowing out highlights you wish to retain.
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Old 01-12-2015, 06:05 PM
Rex Rex is offline
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Re: Photoshop ACR and Exposures

Wow; very interesting. Don't know what I assumed but thought that I knew all about correct exposure having grown up with Velvia.

Now you have given me a link that throws the cat among the pigeons! Does this mean that to get the best RAW exposure, I should be slightly over exposing the image?

I don't mind boosting the exposure in ACR, but somehow, +1.5 seems more than would give the best result.

Guess is it back to the digital exposure drawing board!

Toodle pip,

Rex
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Old 01-12-2015, 06:12 PM
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andrewrodney andrewrodney is offline
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Re: Photoshop ACR and Exposures

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Originally Posted by Rex View Post
Does this mean that to get the best RAW exposure, I should be slightly over exposing the image?
No, not if we agree upon what 'over exposure' means. Optimal exposure is one where you do not blow out any highlight data you wish to retain. IF you do that, you over exposed. Raw and JPEG need different treatment for optimal exposure, just as you would treat an ISO 400 B&W neg film differently than an ISO 100 transparency film. And you can't separate exposure and development, that's photography 101! The 'normalize' exposure processing for the raw is just that. Proper development for that exposure and for that data.

See: http://www.luminous-landscape.com/es...exposure.shtml
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Old 01-13-2015, 03:17 AM
Rex Rex is offline
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Re: Photoshop ACR and Exposures

I hear what you are saying but if the camera preview is jpg and is an electronic assessment of what the RAW looks like, but in reality, is not the RAW exposure, what can one do?

Slight overexposure to move the RAW curve to the right? Or adjust by +1.5 in ARC? Seems like one is damned if you do and damned if you don't!

Guess I will have to run a few tests.

Rex
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Old 01-13-2015, 10:01 AM
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Re: Photoshop ACR and Exposures

Quote:
Originally Posted by Rex View Post
I hear what you are saying but if the camera preview is jpg and is an electronic assessment of what the RAW looks like...
It isn't! The raw is vastly different from the JPEG. The JPEG is one interpretation just as you could produce many yourself from the raw. IF you expose for an optimal JPEG with in-camera processing, you are effectively under exposing the raw data. Again, you can't separate exposure from development, either in film or digital. The JPEG is one kind of exposure and development from the camera.
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Slight overexposure to move the RAW curve to the right?
It's not over exposure, it's optimal exposure. Exposing the raw like the JPEG is under exposure of the raw data. Think of it that way.
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Seems like one is damned if you do and damned if you don't!
Not at all unless you simply have to capture raw+JPEG, then one suffers. If someone handed you a camera that in theory could shoot two pieces of film at the same time, one was ISO 100 transparency film, the other ISO 400 B&W net, you'd be in the same situation.
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Old 01-13-2015, 02:32 PM
Rex Rex is offline
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Re: Photoshop ACR and Exposures

Believe it or not, I did make a a good income from shooting 6x7 Velvia for stock in the days of film, so I do understand correct exposure.

But my point is, if the camera screen only shows a jpg and histogram for a that jpg, and it shows it to be correctly exposed, but RAW ideally has an 'optimal' exposure, the histogram of which is not shown, then how does one know if one has the best exposure for RAW? If the difference is up to 1 stop, and I therefore give everything +1 at the shooting stage, the histogram will show over-exposure. or am I missing something here?

I only shoot RAW, not RAW + jpg.

Rex
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Old 01-13-2015, 02:39 PM
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Re: Photoshop ACR and Exposures

Quote:
Originally Posted by Rex View Post
Believe it or not, I did make a a good income from shooting 6x7 Velvia for stock in the days of film, so I do understand correct exposure.
So did I.

Quote:
But my point is, if the camera screen only shows a jpg and histogram for a that jpg, and it shows it to be correctly exposed, but RAW ideally has an 'optimal' exposure, the histogram of which is not shown, then how does one know if one has the best exposure for RAW?
Well yes, that is the rub, the Histogram and camera preview is a big fat lie if you are thinking it refers to the raw, it does not. We would all be best served if the camera manufacturers would give us a raw histogram. You can get this on Canon systems with a different firmware from Magic Lantern and rumor has it, Nikon might do the same for some of their systems. Trust me, lots and lots of photographers who understand the big disconnect between raw and JPEG want a Histogram that actually represents the raw data, NOT a JPEG we never end up with.
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Old 01-14-2015, 05:39 PM
Rex Rex is offline
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Re: Photoshop ACR and Exposures

So I have been playing around today, shooting a bunch of test c**p, manual metering (as I usually do) 5 brackets at 2/3 stop difference and looking at the best histogram in ACR.

Of course, it depends upon the subject, but generally the +2/3 or +1.5 over are the best for general brightness and anything that was clipped in the highlight, and there is plenty, could be brought back with the -2/3 exposure. Alternatively, I take the middle exposure (correct on the camera screen) and give it about +1.5 in exposure boost in ACR.

But then I thought of doing it differently; open the middle exposure in ACR and hit the Auto button. It certainly looks a better image, but what I notice is that the exposure slider is still 0 but the Brightness slider has jumped to around +60 (or more.)

What is the difference in image quality between brightening the image via exposure or brightness? Presumably Brightness is a gamma move or is it more akin to the middle levels slider (which I almost never use.)
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Old 01-14-2015, 05:47 PM
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Re: Photoshop ACR and Exposures

Ideally you do all the work top down, left to right in ACR. You want to get as much done overall using Exposure, then move down to Highlights, Whites etc. Not sure what version you're using as Brightness doesn't appear on my end, sounds like you're using an older version prior to Process Version 2012 which is MUCH better for processing!

Do you happen to also own Lightroom? Same process engine and controls but what is really nice is that as you move your cursor over the sliders like Exposure, Shadows, Whites etc, you see where on the Histogram that slider will affect the tones.

On my Canon 5DMII, 1.5 over what the meter states is about the limit I can go but YMMV.

Also examine the noise in shadows between the recommended exposure based on JPEG and the one you added more exposure to.
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