32-bit HDR in Photoshop CS2

hi all,

 

i was wondering how many people have played with the merge

feature/HDR (high dynamic range) in Photoshop CS2. apparently you

just bracket a series of images, use the merge tool, and it takes

the best parts of the bracketed images and makes a really great pic.

does anyone have any examples they can post?

 

thanks!

nick

I've played with it. Looks like a feature in search of a problem. 95% of the time the results are pretty blah. I'm sure it will be useful in some circumstances, but I'm equally sure it's one of those things that's more likely to be abused, yielding some pretty awful "digital" landscapes.

 

It's a nice tool to have, but limited in application. You need a static scene and you have to realize that a dynamic range of 15 stops often doesn't look natural. It's not automatic either. You have to do signifcant tweaking to get a printable or viewable 8-bit image out of it.

I haven't seen CS2 yet, so I can't comment on their HDR merge feature, but I have merged HDRs with HDR Shop and used them quite a bit in video compositing and 3D rendering. A visual effects house where I recently worked is probably typical in forming their entire workflow around floating point, high dynamic range image formats, and one essential application that didn't support them was Adobe Photoshop. I don't know if adding HDR capability in Photoshop was largely catering to the needs of visual effects artists, but it is immediately useful to them, probably more so than to your average fine art photographer/print maker. A little more contrast control can help make a nice print, but the extra dynamic range is essential for things like preserving highlight detail reflected in 3D objects.

I believe Mike is correct. This is a feature catering more towards the CG community. Their forums are full of praise for this feature since so far they needed either specialized equipment or buy expensive HDR probes to create HDR lighting effects. The extra bit depth really comes into play in 3D lighting.

 

For photographers, three stop ND is quite the limit for practical situations. For digital layering, merging two shots with 2 or 3-stop exposure difference should take care of most situations.

Agree with Bob. I have played with it a bit, and the results I got looked very "plastic" compared to taking images and combining by different exposure values and masking. Maybe I have just not got the hang of HDR yet!

I've used it several times at this point. I'm pretty certain it does not discard image data; its effect on noise suggests that some sort of scalar combination algorithm is used. Maybe "HDR" refers to a standard algorithm, but if so I don't know what it is.

 

There is also nothing automatic about the feature in Photoshop. After you do the stack, you end up with an image with a huge dynamic range, otherwise normal except expressed in 32 bits. (Nice to finally see 32 bits in Photoshop after working with 32 bit FITs for a decade....) So you can expect to spend time processing to get the output right. I suspect unskilled processing accounts/will account for most of the poor results that Bob mentions and that I fully expect to see as well.

 

I have nothing but test images at this point, and my experiences with them suggest that I need to modify my capture practices if I plan to use HDR. I don't presently have any decent-looking results but I can see the occasional utility of the feature.

 

The following shot is an early test. In the original, when the sky is averaged to gray, the trees are silhouettes, all those pixels are under 15 counts and all detail is lost in the noise. I've overdone it as you can see, bringing everything up much too far, but the fact that you can see the leaves tells me the feature works fine, it is my wetware that isn't up to snuff just yet.<div></div>

I would not base my decisions on whether or not to use it on other people's experiences at this point. It is a new feature and people still need to get the hang of it. Experiment for yourself. I think it is a fantastic technology. The landscape crowd, especially, likely will grow to love it. Combined with the Shadow/Highlight tool, the sky is the limit.

 

If cameras could bracket shots quickly enough, HDR could be used in dynamic scenes too. If you want to use HDR but do not have CS2, try Photomatix: http://www.hdrsoft.com/

There was something about this the other day bu the post was deleted.

 

Anyways, i have found that in colour it can look a bit funny. I have done a little experiment of my own. I apologize for the awful picture but it shows the advantages of this technique

 

6 images over 5Ev stops. At iso 800 on D70 f8.

 

Detail is retained well in the shadows (the screen, bulb, window) but shadows are detailed (under the sink, bed, behind the wardrobe)<div></div>

However, when converted to black and white (the lightness channel in LAB mode) the image is not so bad (IMO). To me it looks like a well exposed negative that has the potential for easier print making (in the darkroom)

 

Just my views<div></div>

just like to point out these images do not look like what i saw on my PS window but you get the point

<p>One aspect of the HDR feature I was disappointed with was the fact that I couldn't find a way to hand-align the images to be merged; Photoshop insists on aligning the images automatically.

 

<p>This is a problem when you don't have a tripod available. I've successfully merged multiple hand-held exposures of the same scene in the past by using layers and hand-painting the layer masks. In fact, I sometimes take grossly misaligned shots from the same scene if I know the areas I will be merging are simple textures, like the sky or rock, where precise alignment won't be a problem anyway.

 

<p>There doesn't seem to be a way of using HDR in this way; the images have to be perfectly aligned from a tripod, or they're useless. This makes the feature significantly less useful for me.

 

If I am missing something about the HDR feature, I would love to be pointed in the right direction!

 

I believe this image was put together from just two exposures from a tripod using HDR. It's nothing you couldn't do by hand, but getting the initial image in PS was pretty snappy.

 

<p align="center"><a href="http://www.photo.net/photo/3396843"><img src="http://d6d2h4gfvy8t8.cloudfront.net/3396843-sm.jpg"></a></p>

You want <a href="http://www.gregdowning.com/HDRI/stitched/">HDRI stitching</a>.

I also posted in the other, now deleted thread.

<p>

I think the key is restraint; it's very tempting to create images that have such wide dynamic range that, when rendered to include all the

shadow and highlight detail, are flat and lifeless or that just look freakishly wrong.

<p>

I've tried the feature exactly once so far, on a cliche sunset near Big Sur, CA. I'm no nature landscape photographer, and this sort of photo

really isn't my thing, but sunsets seem like an obvious choice for playing with this feature. Anyway, I measured 12 stops, and tried to

get all of them (using a D2x, an 85mm/1.4 lens, and a tripod).

<p>

After much fumbling around with curves at the 32 bit conversion stage

and in the 16 bit photo, the result I like best so far (and that

captures detail across 12 stops is at <a href="http://www.crypto.com/private/hdr-sunset-cliche.jpg">http://www.crypto.com/private/hdr-sunset-cliche.jpg [link]</a>.

<p>

One thing I noticed was that it is very hard to avoid moving the camera when changing the settings; auto bracketing is really a better way to do this.

<p>

Anyway, this image, for all its cliched dullness and uninteresting composition, is considerably more detailed in the shadows and highlights than I was able to get with any of the single captures that I merged into it, and probably better than I could get with an ND-grad. But I've still got a long learning curve to climb with this feature before I can tell whether I'll be using it routinely.

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

<i>One aspect of the HDR feature I was disappointed with was the fact that I couldn't find a way to hand-align the images to be merged; Photoshop insists on aligning the images automatically.</i><p>

 

Then do the RAW conversion, align the images as layers in a single file using difference mode, crop it, save the layers to individual files, and then use Merge to HDR. i.e., it will let you, but it will only let you do it yourself it will not do it for you. And alignment is best done with two layers (or more) using difference mode and 400% zoom IMO. Using difference mode you minimize the difference (make it darker) which is much simpler than trying to measure the difference with your eyes. <p>

 

Beyond that, in regards to algorithms for HDR, there are <a href="http://citeseer.ist.psu.edu/cis?q=hdr&submit=Search+Documents&cs=1">many</a>

out there and Adobe does not appear to be talking about what they are using (albeit, I have not looked hard either).<p>

 

In practice, the only effective use for it I have found so far is to reduce noise (especially in the shadows). The scene need not have a high dynamic range as simply bracketing by 5 stops (-2.5 to +2.5 EV) will shift your shadows into the midtones and highlights where the signal to noise ratio is higher yielding less noise and better color in the shadow details. Hopefully I will get a chance to grab some bracket sets of a stream on a sunny day soon to try it out in a situation where both shadow and highlight detail matter. But that is a low priority.<p>

 

some thoughts, <p>

 

Sean

HDR images do typically look flat and boring. We humans take a real life HDR scene and "burn and dodge" it as we scan over it, by opening up and stopping down our eyes, adjusting visual sensitivity, etc. all subconciously.

 

To do that in an HDR image on a computer, you need to either burn and dodge manually, or apply a local "tone mapping" algorithm such as PhotoShop's own "highlights and shadows" feature, or ASF's "Digital DEE". Either of these requires a bit of practice to get used to, but can restore the "snap" to a HDR image.

 

Have fun

 

Joe

I would particularly draw your attention to <a href="http://www.luminous-landscape.com/tutorials/hdr.shtml">this</a> and this: