SNS-HDR Forum

I used the new version 2.5 for the first time today and noticed something strange.

1. Given identical settings, the output varies significantly depending on colorspace. Images processed in Adobe98 are lighter than the same images processed in ProPhoto or sRGB. I even processed some monochrome images and got the same difference.

2. The preview inside SNS does not match the output. The difference is slight and varies depending on the colors. More saturated colors appear to have more difference. I'm using a NEC 2490 monitor calibrated with Spectraview. I've checked all settings to make sure SNS and Photoshop are using the proper profile.

I still have old version 1.4 installed, so I tested it. Previews there match the output exactly.

I didn't make any changes in color profiles. Differences in brightness will occur because the color spaces have different gamma curves. However, these differences should be small. Do you have monitor profile enabled in SNS-HDR?

I'm not sure I understand how different colorspace gamma curves would give different results in SNS. If I switch an image between Adobe98 and Prophoto in Photoshop there is no change in brightness. Likewise, if I feed an image in Adobe98 and then Prophoto to many other plugins or utilities, there is no change in brightness. Only SNS shows a change.

Do these SNS processed images look reasonable to you?





P.S. Yes, my SNS has the proper monitor profile selected.

Do you change the color profile in SNS-HDR or load images with different profiles?
SNS-HDR does not convert color profiles, it only applies profile when you change it (except for saving in sRGB).

Sebastian Nibisz wrote:Do you change the color profile in SNS-HDR...

I don't see any option to change color profiles inside SNS. I see the option to convert to sRGB on output, but I never do that.

I load SNS with 16 bit tif files created by Adobe Camera Raw. Sometimes in Adobe98, sometimes in Prophoto. PhotoMatix, Aurora HDR, Oloneo, HDR Efex all produce identical results when a set of images is processed in Adobe98 or Prophoto. Identical, at least, within a standard deviation of 0.5 or less. Those other HDR results are inferior to SNS, but at least they are consistent. Ditto for other standalone programs like the Topaz utilities.

Here is an example of the preview issue. To create the SNS preview version I displayed the image at 100% in SNS and did a screen capture (ctrl-Prtsc in Windows). Then I created a new document in Photoshop that is the size of my screen and is set to the color profile of my monitor. I pasted the screen capture into this document, and then converted that to sRGB.

A screen capture is made in the color space of the monitor, and is not "tagged". When you paste it into a Photoshop document there is no colorspace conversion made, thus an error. It's the same result as doing an "Assign Profile" in Photoshop. Pasting into a document that is already in the monitor colorspace avoids this error.

This is a highly saturated image, so the difference between the preview and the actual output is significant and easy to see. Load these images as layers in Photoshop and toggle for the best view. Again, I don't recall seeing this issue in previous SNS versions. When I tested this same image under the old SNS version 1.4 there was no difference.

You can change the color profile here.


What have you set here?

Here are my settings.

Also, what us the new "Auto Luminance" switch? I ran a batch with the switch on and off and didn't see any difference.

You do not have the monitor profile enabled, because the monitor profile is not selected.


When Auto luminance is enabled then the histogram is stretched before image processing. Left enabled, right disabled.

Sebastian,

Thanks for the help. With my monitor profile enabled there is no difference between previews and actual. So that problem is solved. I don't know how I missed that, and I apologize.

That leaves the Adobe98 vs. Prophoto difference which is not really an issue as long as what you see is what you get. I'm just still confused why SNS-HDR is the only program that behaves that way.

As for Auto Luminance - I ran 5 different image sets with Auto Lum on and off. I still saw no difference on screen. But when I layered them in Photoshop and used Difference mode, then small differences showed up. Certainly nothing like the sample you gave, but standard deviations around 0.7 to 0.9. A Threshold layer showed differences only up to level 6.

SNS-HDR = still the best.