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PercepTool 2

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  #1  
Old 12-12-2010, 04:31 AM
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PercepTool 2

PercepTool 2 is an HDR plugin for Photoshop that comes with a couple of very unique features: George DeWolfe and Chris Russ. George is a master printer who has made the rare successful transition from darkroom to digital. Chris is one of the most respected technical imaging engineers in the business (and not a stranger to these forums).

Anyway, Chris emailed me and asked for feedback on PercepTool 2. Download the trial, kick the tires, and post back here with your findings.

http://www.georgedewolfe.com/perceptool.html
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Old 12-12-2010, 02:24 PM
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Re: PercepTool 2

I have been doing considerable benchmarking of various HDR S/W recently so I took PercepTool for a spin on some of my bracketed test image sets.
My 1st and probably most important test is how the s/w handles highlights. If it fails there, then all of the fancy interfaces and presets, and frills don't matter. At that point the testing is pretty much over with a failing grade. There are ways to work around the problem, but a lot more work and fiddling is not what I am looking for.

The good news is that PercepTool gets a pass. It is not as good as Photomatix which I find superior to the all others including Nik's HDREfexPro, Oleono Photoengine, and PhotshopCS5's Merge to HDRPro with PS being by far the worst. PercepTool comes pretty close to blowout of the highlights but just manages to keep it from hitting the top limit. However compared to Photomatix it does wash out a fair amount of the detail in those highlights.
I was not particularly impressed with the shadow detail. I found the shadows too dark and lacking detail. Performance here was about middle of the pack.
Noise performance was good. The best noise performance by far was Nik HDREfexPro followed by PercepTool.
I do not like the way the program is chopped into 3 pieces and the fragmented workflow:
-Run the PS script to open and load RAW files into a stack or process each image your self then load and stack.
- Run the HDR blend / tonemapping with no controls or adjustments
- Run the Equalizer Filter
- Run the PercepTool filter to do Gamma, Exposure, etc (most people would prefer to do this stuff in PS).
I can post a few image comparisons if you like.
Regards, Murray

Last edited by mistermonday; 12-12-2010 at 10:38 PM.
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Old 12-12-2010, 02:28 PM
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Re: PercepTool 2

Did you get to try it in 32 bit? I suspect that's where it shines (and kind of the reason they wrote it).
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Old 12-12-2010, 02:38 PM
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Re: PercepTool 2

I had PS open and stack 5 aligned RAW files (16 bit NEF) and then ran the HDR Filter on them. The resulting default image was the test point. I did not convert that to 32 bit nor should I have had to. Or am I missing something?
Regards, Murray
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Old 12-12-2010, 03:38 PM
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Re: PercepTool 2

As I understand it (and I'm not promising that I do), it's not that you have to, but that finally you can. That's one of the reasons I wanted to get it into the hands of some experienced HDR fans, to see if 32 bit actually makes that much difference.
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Old 12-12-2010, 04:08 PM
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Re: PercepTool 2

The 32 bit file is produced by the HDR merge. Most HDR s/w uses this 32 bit file as an interim file which it discards after performing the tone mapping to an 8 or 16 bit output. Most of the s/w also gives you the option to save that 32 bit file as well so that you can play with it in PS or other s/w.
The issue is that the initial merged default image produces unsatisfactory results. I can process the resulting 16 or 32 bit image in PS or in PercepTools Equalizer or a umber of other s/w options. However that is not what I want to do. I am looking for a merge that gets the image to where I need minimal tweaking and do not need to spend time recovering blown highlights or enhancing shadow details. So far Photomatix is the only product I have found that does that and it does it almost 100% of the time. The other products so all fail at the 1st and most critical point.
Regards, Murray
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Old 12-12-2010, 06:43 PM
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Re: PercepTool 2

Oh, where to begin.

I'm one of the authors of PercepTool. As you've observed above there are indeed three parts, and I'd like to outline them, what they're for, why they are separate, and the advantages of 16- and 32-bit modes respectively.

Let's start with HDR Align and Blend.

One problem that I encounter as a photographer is alignment of my images, even when taken on a heavy duty tripod. If you are going to perform HDR, you either must align the images manually, or depend upon the software to do a good job. I discovered, much to my chagrin, that Adobe's alignment results are inconsistent. Even with the same images. So the first part of HDR Align and Blend is designed to solve the alignment problem -- we align several times (user selectable) and pick the best fit. The stack of images is then nudged to match.

You could stop right there and use some other tool if you wanted, or you could continue on with the Blend part and we produce a really acceptable HDR blend that pays close attention to color, especially in the midtones. In the head-to-head comparisons that we did, we had a much more faithful treatment of color and saturation than did the other tools out there (remember, I'm the guy that wrote it, so you really should test it yourself). And as is common to HDR images blended in this way, they tend to lose saturation in the highlight areas and we did something to address that (Color Correction).

I also put a lot of effort in to making a low-noise result. The first version of HDR merge in CS2 kept the pixels that were MOST DIFFERENT than their neighbors -- essentially a noise detector. If your image has lower noise, you can perform more sharpening or other steps. If it has higher noise, there are very few things that can be done to an image to make it better.

The kicker is that we did it in 8- (works, but not recommended), 16-, and 32-bit modes. Doesn't seem like a big deal.

Q: Why 32-bit mode? A: Because out-of-gamut colors don't clip. Because your highlights won't go away during processing.

A lot of people poo-poo 32-bit mode but it does have that tremendous capability of preserving your highlights, colors, and detail within those highlights so you can decide later how to adjust the image and bring everything into a more narrow dynamic range for printing.

HDR Align and Blend is scriptable and actionable -- you can record it for your own secret sauce. You don't have to use the whole thing. THAT is the point about breaking PercepTool into different pieces, because none of us like to be dictated to.

-----

The Equalizer tool.

This is a unique multi-scale contrast (tone-mapping) tool. You don't have to have an HDR image to use it. It does really nice things for normal photography, but can be especially useful for HDR Photography where you have to deliberately throw away parts of your image to see other parts. The whole point of dynamic range reduction is to make an image that shows the important (to you and the viewer) parts of the image while eliminating or reducing the parts that don't matter. The kicker is doing it in a visually believable way.

Remember, we have two different parts to the human visual system and they don't work the same way:
1) The peripheral visual system basically makes a gross luminance (and some color -- not much) map of the whole image, and the resolution drops as you get farther from the center of your field of view
2) The central visual system (also called the Foveal visual system) is about the size of a thumbnail at arm's length and is the high-resolution part of your visual system. Basically people look at different things and "hang" those high resolution bits on the overall gross luminance map. Our brains make these pieces seem seamless, and we're quite good at assuming details that we never actually looked at because we recognize familiar objects and move on. (This is one reason that JPEG compression works.)

Any tone mapping (or contrast) tool is going to need to work well with both systems. Sadly, tools that work well with the peripheral system tend to leave lots of halos. Tools that work well with the central system don't deal well with gross brightness changes across the field. In my experience, halos and the 'grunge effect' aren't acceptable if you're trying to make a believable image.

The era of 'grunge' HDR photography is coming to a close, and tools that leave nasty halos behind are going to have to go with it.

The Equalizer is designed to affect seven different size ranges, two with radii over 2000 pixels -- something you cannot do in Photoshop or any other tone mapping tool. Something that is essential if you have a high resolution image and don't want to see a halo. For those interested, there is a book called "Vision" by David Marr that might be interesting.

It is also completely scriptable and actionable and you can record settings to put into your own secret sauce for processing images.

-----

Finally, there is the PercepTool.

PercepTool uses the primary image's display, not a proxy view, and is designed to bring back the "punch" in images. Very literally, What You See Is What You Get. Not only does it do a halo-free sharpening as part of the PercepTool Effect, but it also uses a very non-linear method of finding local shadows to bring "presence" back to the image -- to make it more like the scene seemed when you took the picture in the first place.

There certainly isn't a requirement that the image be from an HDR source, but it can work quite well on those images. And, if you are working in 32-bit mode, you can get a histogram of your image, something that Photoshop will not let you do.

-----

There is a lot of stuff here. Some or all of the pieces might fit into your workflow into a number of places, whether you shoot HDR or not, whether you find 32-bit mode useful or not, whether you have CS4/5 Extended or Normal.

This wasn't written in a vacuum and the functions are not so simple that someone can come along and say "Oh, it's just _blah_blah_blah."

That being said, with a 30-day demo period, you can find out for yourself if there is any "there" there.

(Sorry to go on for so long, but I couldn't leave things the way they were upthread.)
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Old 12-12-2010, 08:32 PM
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Re: PercepTool 2

JCR6, thanks for the additional information on PercepTool. As mentioned above your noise performance is very good and in most your ability to retain highlight detail is better than any product I have looked at except Photomatix. I agree with your comments about the grunge look soon becoming a fading fancy, and I don't think that is what HDR is all about. My biggest concern has been and continues to be blown highlights upon merge to HDR. I have attached a sample below of PercepTool and Photomatix. To be fair, no adjustments were made to the RAW files, no sharpening, no denoise, no Chromatic Aberation mitigation, etc. No post adjustment were made to either file after merge. The images were converted to sRGB for browser view and are low res but the areas of concern can be readily seen.
You will see a clear difference in the bright highlights which have been almost 100% preserved by Photomatix. PercepTool has pushed them pretty high and where they are not blown, the detail is reduced. There are no control options prior to or during merge and I am finding it very difficult or impossible to make correct for it after merge using Equalizer or PS. I could modify the RAW files or I could exclude the overexposed ones but that would not be an effective way to work. I would welcome any thoghts you might have in this regard.
I did not attach any samples of the shadows. They are definitely darker than Photomatix but the shadow detail can still be recovered so I am not too concerned.
Regards, Murray
Attached Images
File Type: jpg PercepTool Highlights MM1.jpg (147.9 KB, 40 views)
File Type: jpg Photomatix Highlights MM1.jpg (169.7 KB, 39 views)
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Old 12-12-2010, 09:51 PM
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Re: PercepTool 2

How do you feel about the color rendition in the Photomatix output?

--------

It is difficult to be fair to you and your aesthetic, while at the same time trying to point out where I consider the PercepTool result superior.

Personally, I consider pumping up the saturation a late processing step, largely because colors can easily go out-of-gamut. (We should talk about 32-bit images sometime.) I also see some colors rendered in the Photomatix image (magenta in a blue-white highlight) that don't appear to be real. Not having the original images, it's hard to comment, but to me color fidelity is an issue. Photomatix problems with color showed up in our testing.

You did say something upthread that seems to summarize the difference between your approach and mine: You want a one-stop "do-it" kind of tool. There is absolutely nothing wrong with that.

Me, I'm a Photoshop junkie that likes control. I record my own actions or scripts with the steps that I like and with PercepTool 2 I tried to provide a bunch of tools for people that like that level of control. Some of my users spend a lot of time on each image, per George's workflow.

The PercepTool suite is intended to add to a Photoshop user's tool set. It's not just for HDR, but does a good job of HDR when you want to.

HDR isn't the whole story -- the Equalizer draws from Edward Land, David Marr, Jean Babtiste Joseph Fourier and others.
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Old 12-12-2010, 10:37 PM
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Re: PercepTool 2

Quote:
Originally Posted by jcr6 View Post
How do you feel about the color rendition in the Photomatix output?

--------

It is difficult to be fair to you and your aesthetic, while at the same time trying to point out where I consider the PercepTool result superior.

Personally, I consider pumping up the saturation a late processing step, largely because colors can easily go out-of-gamut. (We should talk about 32-bit images sometime.) I also see some colors rendered in the Photomatix image (magenta in a blue-white highlight) that don't appear to be real. Not having the original images, it's hard to comment, but to me color fidelity is an issue. Photomatix problems with color showed up in our testing. I agree with your comment on saturation. The saturation control is makes it easy to dial it up or down. There is a strong Chromatic Aberation in the originals and the building is surrounded by water, colored roofs, and other buildings with colored glass. I will take a look at the color pollution but I can also believe that Photomatix may be inducing some of it. BTW, I forgot to mention above that PercepTool was the only product aside from Photomatix that did not induce strong color casts in many merged images. Some of the competitive products strongly shift saturation when exposure or other sliders were tweaked.



You did say something upthread that seems to summarize the difference between your approach and mine: You want a one-stop "do-it" kind of tool. There is absolutely nothing wrong with that.

I am not looking for a one - click tool. I spend a fair amount of time making additional adjustments to get the image right. What I do not want to do is spend a lot of time compensating for blown highlights unless there is no other solution. I used to do a number of things including copying blown pieces from one of the source files and masking them into the merged image or preprocessing the RAW files before merging to ensure the highlights would not get blown. However, if I can achieve a merged file without having to go through that hassle, that is preferable.

Me, I'm a Photoshop junkie that likes control. I record my own actions or scripts with the steps that I like and with PercepTool 2 I tried to provide a bunch of tools for people that like that level of control. Some of my users spend a lot of time on each image, per George's workflow.

The PercepTool suite is intended to add to a Photoshop user's tool set. It's not just for HDR, but does a good job of HDR when you want to.

HDR isn't the whole story -- the Equalizer draws from Edward Land, David Marr, Jean Babtiste Joseph Fourier and others.
The PercepTools are definitely impressive and I can see their value as part of the PS tools set. I think if your algorithm were refined to preserve the highlights a little better you would have a more successful product

Regards, Murray
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