Exposure Blending with Stack Images

[den]

Possible enlightening approaches on the DPR Retouching forum regarding exposure blending [although the OP is using HDR terminology] is posted here: http://forums.dpreview.com/forums/read. ... e=35392068 .

Interesting to see the PS folks' struggle with something fairly easily doable with PWP's Stack Images and symmetrical and asymmetrial tone range Amount masks...

ExposureBlending01_400px.jpg (48.41 KiB) Viewed 8002 times

If there is further interest, I can detail a PWP solution...

[cliff]

Hi den,
I would appreciate an explanation of how you did it. I've been having some trouble with the Stack Images transform. Your solution looks very good, except, to me, the interior is a little too bright.
Thanks,
Cliff

[den]

Cliff... thanks for the interest. I will work something up and post again later tonight/tomorrow. You are right, now that my office does not have any sunlight coming in... the interior is too bright. Easy enough to adjust with a Amount mask slider change and/or a 'contrast mask'/Softlight to tone balance the overall image elements.... till later.

den

[den]

Okay.... here is what I did...

(1) Downloaded the DPR forum OP's "beforeafter","-1", and "-2" jpegs from http://forums.dpreview.com/forums/read. ... e=35392068 and then cropped the "beforeafter.jpg" in half to create registering 'before', '-1', and '-2' jpeg images, 335x500 pixels each.

(2) Created a symmetrical tone range Mask1 [has the same gradient from a 50% tone to the mask's white (100%) and black (0%) image areas] to be used to blend the 'before' and '-1' images by:
Click on the 'before' image and open the Mask Tool - BrightnessCurve; lower-left Apply Add a StairStep curve=[0,0], [95,0], [95,100], [100,100]; lower-left Apply a Blur=25; and click OK, creating Mask1. Mask1 looks like this:

SIAmountMask1-200px.jpg (3.19 KiB) Viewed 7897 times

(3) Created an asymmetrical tone range Mask2 [has differing gradients from a 50% tone to the mask white (100%) and to the mask black (0%) image areas] to be used to blend '-2' highlight tones into the the primary blending of the 'before' and '-1' images to retain/provide curtain shear detail by:
Click on the '-2' image and open the Mask Tool - BrightnessCurve; lower-left Apply Add a BrokenLine curve=[0,0], [30,0], [40,100], [100,100]; lower-left Apply a Blur=10; lower-left Apply Subtract a BrokenLine curve=[0,100], [10,100], [30,0], [100,0]; lower-left Apply Feather=-2; lower-left Apply Feather=+2; and click OK, creating Mask2. Mask2 looks like this:

SIAmountMask2-200px.jpg (6.88 KiB) Viewed 7908 times

(4) Then, click on the 'before' image and open the StackImages transform, leaving individual Curves [PWP5]; Final Shaping Curve [PWP5]; and Density Masks off. Add Input images and Amount masks as follows:
Image 1: Input='before'; Amount mask=Mask1; white=0; black=100
Image 2: Input='-1'; Amount mask=Mask1, white=50; black=0
Image 3: Input='-2'; Amount mask=Mask2, white=25; black=0

Further adjust Amount mask whites and blacks while monitoring an updating Preview to a preference, and then click OK, creating the exposure blended image.

PWP5 users could also adjust the Final Shaping Curve to a preference before clicking OK. Others could use the HSV BrightnessCurve transform.... or Both use a slightly blurred 'contrast mask' and Composite-SoftLight to tone balance image elements brightnesses on the resulting (4) image.

The only real difference from the above workflow to the DPR OP's method was to better define/form Mask1 and Mask2 for the blending of the exposure images... avoiding halo and tone reversal artifacts.

The mask creations are not necessarily intuitive and are image set specific. The general approach was to primarily blend the properly exposed image areas of the 'before' and '-1' images using a symmetrical tone range mask and secondarily blend the '-2' image highlights using an asymmetrical tone range mask with the corresponding '-1' image areas. The mask Blur amounts are scaled to the 335x500 pixel images but the curves and Feathering would be suitable for full sized images if available.

Anyway... once you have the StackImages transform set up, play with the the black/white Amount slider settings while monitoring an updating Preview...

Cliff... you may prefer the Image 1, Amount mask black=50 or 75 rather than the 100; and/or the Image 2, Amount mask black=5 or 10 rather than then 0 as suggested above....

...Also this is just one possible solution/approach...

Ask if there questions...

[den]

Additional Note:
The above approach is no where near the sophistication that Jonathan's white paper: "Stacking Images.pdf" (HDR Techniques) describes and is not meant to be an alternative to his considered design of the PWP5 StackImages transform. It is what easily works for tone range considerations of the specific DPR OP's image set.

[cliff]

Thanks den,
It'll be a couple of days before I get a chance to try this out. I did check on the dpreview forum, and apparently the PS user needed to manually paint the layer masks. PWP one, PS zero.

[cliff]

It turns out that I had some time. I was able to follow your workflow.

But it will take a while before I understand how it worked.

Thanks

[MikeG]

Thanks, Den, for another illuminating tutorial. Obviously the Stack Image transform is a very powerful tool, well worth the effort of mastering. Unfortunately, for me, mastery is as yet beyond my grasp. I was able to follow your example without difficulty and to replicate your results, but going 'solo' - not yet, I fear.
While updating BDSizer (which I, and others, use for resizing images to post to this forum) I noticied another freeware program that IDImager Products offer. It's called Dynamic Range Increase. I downloaded it and gave it a try. Below is the result of -1EV and 'original'.
The program does offer a couple of adjustment sliders. Though not to be compared with the power and flexibility of Stack Images it does offer simplicity!
For anyone interested in experimenting, here's the link:http://www.idimager.com/downloads/freeware
Mike.

[den]

If you read through the DPR Retouching forum thread linked in the OP... "SNS-HDR" is mentioned several times, although its example posted by 'Pebal' [the author] is not really representative. Extraordinary things can be done when its freeware "SNS-HDR Lite" is linked with the editing/data access of PWP's transforms....

http://www.ncplus.net/~birchbay/10/IMAG ... _10_93.htm

Overdone perhaps but done because it could be....

[MikeG]

Here's a link to a Polish site: http://www.sns-hdr.com/

There seem to be three versions.
The Lite version, which is a command line program and which is free.
And two Pro versions, one for home use at 30 Euros and a professional version at 85 Euros.

Elsewhere I've asked a Polish speaker if he'd care to check the site and programs out in detail.

Mike.