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Author Topic: DPP doesn't have a genuine Exposure control?  (Read 6479 times)
Guillermo Luijk
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« on: August 13, 2011, 07:07:59 AM »
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First I must say I am not a DPP user, never installed it. But in other forum someone provided images processed with DPP, the original and the resulting from adjusting 'Bright' and 'Exposure', and I analyzed the before vs after to obtain the curves (level arrangements) that produced the output from the input.
 
I already did this for ACR and Photoshop Exposure, Bright, Contrast,... in this article, and everything was as expected (the Exposure control is a straight line curve starting from (0,0) both in ACR and Photoshop, a genuine Exposure correction).
 
But in DPP it doesn't happen like that.

Bright in DPP:
.

Exposure in DPP:
.
 

Conclusions:
  • What DPP calls Bright, is like the old Bright control in Photoshop CS2, a totally unrecommended adjustment since it destroys highlights information and washes the shadows when pushed, and clips the shadows when reduced
  • What DPP calls Exposure, is a curve like Bright in ACR and Photoshop CS3 and above, and is not a genuine Exposure adjustment
  • A genuine Exposure adjustement in DPP simply doesn't exist (!!!)
Is it possible that DPP doesn't have a proper Exposure control?

If you shoot for instance ISO100 1/500 f/4, and then shoot again ISO100 1/1000 f/4, and develop both RAW files with the same settings in DPP but pushing the second by +1EV, don't you get exactly the same image?

Regards
« Last Edit: September 18, 2011, 08:36:45 AM by Guillermo Luijk » Logged

Sareesh Sudhakaran
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« Reply #1 on: August 13, 2011, 10:22:15 AM »
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I'm very new to DPP, but isn't the brightness slider under the RAW tab the same as Exposure? If you move it left or right, the histogram shifts.

It is by this method that we achieve ETTR low noise files as described by Michael, isn't it?
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Guillermo Luijk
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« Reply #2 on: August 15, 2011, 11:47:48 AM »
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OK, the curves calculated were wrong because additionally to the exposure settings, the images used to calculate the curves had tonal curves applied (even if I asked the users to set everything to 0). I now repeated the exercise with the 'Linear' checkbox of DPP activated (this seems produce a gamma=1 output, which is irrelevant to calculate the curves, just will change their slope, but also ensures 0 processing).

The new curves show now that DPP's Exposure Control is a genuine exposure control, performing on RAW levels the same linear scaling a change in exposure in the camera (aperture/shutter) would have produced:

.
(ignore the end part of the -1EV curve, your images simply didn't have data to calculate the curves there)

I found very strange that DPP's didn't have a proper exposure adjustment, it's a basic tool (and besides the easiest to implement in the code, just need to multiply levels by a constant factor: 2.0 for the +1EV, and 0.5 for the -1EV). If using a linear profile, the same is achieved in PS with:
 


Regards
 
« Last Edit: August 15, 2011, 11:59:27 AM by Guillermo Luijk » Logged

PierreVandevenne
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« Reply #3 on: August 17, 2011, 07:06:43 PM »
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I'm very new to DPP, but isn't the brightness slider under the RAW tab the same as Exposure? If you move it left or right, the histogram shifts.

It is by this method that we achieve ETTR low noise files as described by Michael, isn't it?

If you mean take an actual picture in RAW that looks in most cases overexposed as jpeg but isn't actually clipping, then adjust it "down" (or left), yes. I am amazed at how much controversy and sterile discussions this topic generates. You simply get as much light as you can, without overflowing the wells/saturating the sensor. That's the "absolute" best exposure you can take. The only problem is determining how your camera behaves in terms of previews, determining the relationship between what the camera shows in terms of preview and histogram of that preview and the actual data it has acquired. Of course, your creative needs (or obligations - shutter speed for sport for example) have the priority. But if you have the freedom, simply up the signal to the max without clipping.
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Nigel Johnson
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« Reply #4 on: September 18, 2011, 08:28:26 AM »
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...I already did this for ACR and Photoshop Exposure, Bright, Contrast,... in this article, and everything was as expected (the Exposure control is a straight line curve starting from (0,0) both in ACR and Photoshop, a genuine Exposure correction).

Guillermo

The link in the above post won't work without editing, you may like to edit it.

Regards
Nigel

PS Interesting post and linked article, thank you.

(typo edited)
« Last Edit: September 18, 2011, 08:52:33 AM by Nigel Johnson » Logged
Guillermo Luijk
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« Reply #5 on: September 18, 2011, 08:38:01 AM »
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The link in the above post won't work without editing, you may like to edit it.

Forum engines could agree a standard bb code. Thanks Nigel, fixed now.
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