Photoshop CS2's High Dynamic Range (HDR)

[JDArt]

Has anyone used the new High Dynamic Range (HDR) feature of PhotoShop CS2?

Photoshop HDR 32-bit Format: The Dawn of a New Era?

Adobe added a long list of new features to Photoshop when the released CS2. Of the lot, the one I consider to be the most enticing yet mysterious is the new 32-bit per channel HDR format. Short for "High Dynamic Range," HDR uses 32-bits per channel rather than the usual eight or sixteen bits. And it's how it uses them that makes HDR something truly new.

Just What is "High Dynamic Range?"

Standard 8-bit images use values from 0 through 255 to cover the range from black to white. 16-bit images up the ante by allowing you go from 0 all the way to 65,535. In both though, black is still black, and white is still white. All the extra values that 16-bit provides are slotted in between the standard 8-bit values so we really still have about the same dynamic range for each. We can just represent things more accurately in 16-bit mode.

The main limitation with all RGB systems is that they are geared to describing what color something is, not how bright it is. The CIE L*a*b color model improves things somewhat by separating the color components (the "a" and "b" channels) from the brightness or luminance (the "L" channel), but the range of available brightness values is still rather limited.

To represent the real world, we need a relatively open ended brightness scale, and that's exactly what HDR provides.

Rather than using regular integers (the numbers we count with) to record things, HDR uses floating point numbers. If you've used an ordinary pocket calculator, you are probably already familiar with floating point, but just in case, allow me to explain briefly. Sometimes referred to as exponential notation, floating point employs a fractional number (officially known as the mantissa) which is multiplied by some power of ten (known as the exponent). For instance, if you have a calculator with a nine-digit display that reads 999,999,999 and you add one to it, you get 1e+09, or 1 x 109. Multiply the same number by a million and we'd have 9.99999999e+14. This way, we can keep on counting for a long, long time. Also, no matter how high we get, the precision is retained since the mantissa still has the same number of significant digits. Negative exponents let us get ever closer to zero as well with no loss of precision. For all practical purposes, this gives us essentially limitless dynamic range.

Summary

If, like me, you have traditionally used graduated neutral density filters to compress the tonal range of your images so they can be recorded on film or digital, or if you have experimented with other digital blending techniques, you will probably want to start experimenting with HDR. It seems a foregone conclusion that Adobe will continue to enhance the 32-bit capabilities of Photoshop in future releases. There are also third party applications such as Photomatix, Photogenics HDR and HDR Shop that allow you to work with HDR images. This is the future of digital imaging. While we are only just beginning, the capabilities already are well worth exploring.

http://www.earthboundlight.com/photo...hdr-32bit.html

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I took some shots to try this feature out but haven't had time to process them. Sounds like a great way to enhance landscapes.

[dbphotos]

I'm not the expert, but don't you have to have a 32bit processor to take adavantage of this? How many 32bit processors are out there?

[Paul Shields]

I've been looking into HDR recently - anything that can get me closer to the range I get from a Velvia slide has to be a good thing. Not got round to really trying it out yet, but should be relatively simple using exposure bracketing on fairly static images - and for me an excuse to get a better tripod. As you say, landscapes would be a good candidate.

Edit: hmm, bracketing maybe isn't the best method after reading the link in more detail. Still quite simple to do via the apteture ring though.

[Paul Shields]

Originally Posted by Pavel

all the processors are 32 bit and the AMD64 and Mac G5's are 64 bit. On the topic of velvia slides ... I'm perplexed because slides are already narrower than straight processed digital files. Film has a bit more latitude. The HDR stuff is waaay on up there probably covering a full ten stops is you do it right. It has worked a few times for me ... and I've gotten really weird results as many times too. A few types lend themselves to this but not all - and I expect to see this feature overused ad nauseum as more photographers find out about it. Kinda like fisheye lenses in the early seventies.
I just fininshed rereading an ansel adams book that I first read when I was 15, the camera. It really struck me, with my digital sensibilities, how so many of his shots were exposed in a way we would criticise today. He kept the highlights but often sacrificed the shadows - and boy oh boy do the old shots often have high contrast and no range!
Film is soft too!

Yes - I'm more talking about the quality of light rather than latitude - dynamic range, if you like. Difficult to summise, but I would like to capture something that offers me that light density and the ability to change it at will in processing - maybe HDR can? Dunno, I'll have to try it and see.

Adams - he was the original dodge and burner - had a good eye though !

[deluco]

Must you be using a RAW file to get this HDR feature?

[dbphotos]

Originally Posted by Pavel

all the processors are 32 bit and the AMD64 and Mac G5's are 64 bit.*

OK, that's what I get for being up too late last night. I was getting 16bit vs. 32bit confused with 32bit vs 64bit.

:-[

[karbo]

Here is one I tried a few weeks back. Comprised of several images using PSCS2 HDR. Not the best example but the original file has a huge amount of DR. The biggest challenge was finding away to "spread" all that extra DR out and smoothly convert it to 16 or 8 bit.



Pros:

• Unreal amount of dynamic range and could be extremely useful in situations where movement is not an issue.

Cons:

• sensitive to movement between frames (trees in wind).
• does not seem to allow double conversion of the same raw file must be different true exposures. (would love a simple work around)

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Best regards-

Karbo

http://karywall.com

[paulhodson]

Originally Posted by karbo

does not seem to allow double conversion of the same raw file must be different true exposures. (would love a simple work around)

Even if it did I think the dynamic range they suggest is required in the images exceeds what you could do from a single RAW image. That's why they say bracketing is not adequate

[AlbertP]

This looks like a fantastic feature. I have to try it out.

Karbo, could you tell us how exactly you arrived at the final print? Did you start by underexposing and move up several stops to overexposure? How many frames are required to get what you need?

[Marius]

I think the example above is amazing!!!! You would have to work a LOT to get that kind of result with conventional photoshop techniques. It would be a huge time saver and the results are no doubet better than any film or digital can reproduce alone.

Thanks for the sample.

[paulhodson]

Mind you - it's amazing what a single click of Highlight/Shadow in PSCS2 can do:

[timjon]

I had a play around with this a couple of months ago after seeing a very interesting article on HDR at Luminous Landscape:

http://www.luminous-landscape.com/tutorials/hdr.shtml

Being lazy, and since I was just testing this, I (a) only used three images (-3, 0, +3 ev) and (b) just used JPEG images instead of RAW. I was still pretty impressed, though.

I've played around in the past with layering multiple images taken at different exposures by hand, but this makes it a lot easier and the blends look more natural.

[Paul Shields]

I had a play with the PS HDR feature today. Just took a range of shots of my garden at home from 1/4000 to 1/10. It does give you a heck of a lot of dynamic range to play with, though I found it slightly unreal looking (like a souped-up shadow/highlight tool). The slightest breeze also affected the trees from shot to shot. I'm sure this technique will pay dividends on landscape shots (so long as the mountains keep perfectly still).


1/4000sec at f/2.8


1/10sec at f/22


Final HDR image