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DPChallenge Forums >> Individual Photograph Discussion >> Converting from raw for 2 exposures
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 08/14/2006 09:52:16 AM · #1
I was looking around a few pictures and found this one. One thing I was curious about was how an image is converted from RAW as two exposures and remains in the rules.



What steps would be needed to create this legally. It seems to be similar to HDR.
 08/14/2006 09:55:53 AM · #2
Adjust the exposure for the shadows in RAW, then open the file in PS.
Then adjust the exposure for the highlights in RAW, and open the file in PS.

Then merge them both as you would with HDR. Since it's from 1 file, it's legal.
 08/14/2006 09:56:01 AM · #3
I'm also interested in this answer. Please be very specific, this process seems (to me) to tip toe the legal line.

edit - quick posting, Ben!

Originally posted by KHolt:
What steps would be needed to create this legally.


Message edited by author 2006-08-14 09:57:34.
 08/14/2006 10:02:37 AM · #4
It seems to be one of those things that is technically legal, but pushes the boundaries as much as possible. I've used it a number of times. Basically convert two images from the RAW file, one the the exposure bumped up, the other with it left as shot or bumped down. Copy the two resulting shots into a single file on different layers, and then erase or mask until you've got the best of both exposures combined. It's great for extending the dynamic range of a pic that otherwise might have lost some detail to shadows or blown highlights. Of course, you have to have a decently exposed shot to start with.
 08/14/2006 10:11:57 AM · #5
The technique does fall within the rules, because it uses one source exposure. It doesn't matter that the exposure is "developed" twice. It's essentially just making best use of all the data that's there in the RAW file. It is precisely the same thing as HDR, just limited to one source image.
As the dynamic range of cameras improves, this technique will find more and more use, since the dynamic range of displays and prints is significantly less than that of the source file. DR compression is therefore very useful.
08/14/2006 10:14:04 AM · #6
I don't understand why this is possible in raw and not in Jpeg, I mean what if you use two layers and then flatten them?
 08/14/2006 10:21:34 AM · #7
Really interesting. Think I'll be giving this a go in the future, it could provide that extra punch to some images.

This as far as I can work out would only be allowed in advanced editing challenges.

08/14/2006 10:26:58 AM · #8
@Pano: It really has no benefit in JPEG, you could do the same thing with curves. The benefit in RAW comes from the additional bit depth and dynamic range of the RAW file.

@KHolt: Yes, Advanced Editing only.
 08/14/2006 10:37:25 AM · #9
Aha, thanks Kirbic, i guess is should try i to fully understand it
 08/14/2006 10:49:22 AM · #10


The first is a straight conversion directly from RAW, the second is my final edited version. Details are on the final shot. I intentionally underexposed the scene by about a stop because it's so easy for the bright city lights to blow out in multiple regions all over the photo. Processed as discussed. This was my very first attempt with this method so there are still some chromatic halos due to inexperience in PP, but you get the idea.
 08/14/2006 11:04:42 AM · #11
Originally posted by Pano:
I don't understand why this is possible in raw and not in Jpeg, I mean what if you use two layers and then flatten them?

JPG has 8 bits for each color, RAW has about 13 (depending on the camera). Think of a JPG as an 8 bit window into a 13 bit space. By makeing two JPGs, and sliding the window from top to bottom, you get two photos that seem to be exposed differently.

Raw Shooter Premium allows a lot of control over the RAW file. Is the two JPG method better than RSP?
 08/14/2006 11:06:56 AM · #12
Originally posted by hankk:
Raw Shooter Premium allows a lot of control over the RAW file. Is the two JPG method better than RSP?


I've never looked at RSP, but note that the Photoshop method does not involve two JPGs, it involves two layers in a PS. If your conversion from RAW specifies 16bit, that's that both layers in PS are. JPG is a decision made when you save a converted file.
 08/14/2006 11:25:27 AM · #13


Here is an experiment with one raw file converted to b&w and a colour version - they are combined and offset.



08/14/2006 11:53:25 AM · #14
I'm probably just being daft now, but 'strangeghost' states that it doesn't involve two JPGs, it involves two layers in PS.

Admittedly it isn't two JPGs but it is two seperate photoshop files until they are joined together. Thats where I felt it might be stretching the rules a little.

Or is there a way to open the second exposure as a layer in the first created photoshop file?
 08/14/2006 11:58:33 AM · #15
Originally posted by KHolt:
I'm probably just being daft now, but 'strangeghost' states that it doesn't involve two JPGs, it involves two layers in PS.

Admittedly it isn't two JPGs but it is two seperate photoshop files until they are joined together. Thats where I felt it might be stretching the rules a little.

Or is there a way to open the second exposure as a layer in the first created photoshop file?


In photoshop copy & paste a different duplicate/layer/version over another. Then fade.

Message edited by author 2006-08-14 12:02:26.
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