How To: Single-Image HDR
- This topic has 22 replies, 8 voices, and was last updated Apr 10, 2008 at 11:17 pm by
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Hey guys –
We’ve spent some time bad-mouthing HDR on this board, and to some extent that is fair. When HDR is over done, it can result in a jacked up, unnatural image.
However, the fact remains that the human eye can see a lot broader dynamic range (meaning brights and darks) at the same time than a camera can. This is because the human eye can vary its “ISO” or exposure sensitivity locally in just one area rather than only across the whole image. This is what allows you to see the inside of a darkened room as well as the brightly lit world out the window at the same time. A camera could only see one or the other.
We have a number of situations in streamside photography where we need a broader dynamic range than the equipment allows. The classic situation is one of side light, where light from beside the subject is lighting it (usually a person casting) beautifully, but the background is dark. At times, this can look unnatural.
Let’s take an example image:
Notice how, while the angler is brightly lit, the darks are all unnaturally dark? I could see into the water just fine as I took this image, of course, but the camera was forced to underexpose the dark areas to avoid blowing out the highlights.
What do we do?
Open the image in Photoshop (CS3 here, but most versions can handle this) and immediately grab the highlighted areas using Select Color Range. In this image, I maxed out the Select Color Range slider to 200 to get a broad array of bright pixels (just use the eyedropper to grab the brightest spot you can). I was careful to set my selection tool to 20px of feathering so I didn’t get hard lines.
Once I had all the bright areas, I copied them (use Ctrl-C or on a Mac Command-C to copy), then I pasted them right back down as a new layer (Ctrl-V/Command-V).
Here’s what the new layer looks like with just a white background:
Weird, huh? What you may notice, though, is that the new layer naturally has a lightened opacity. That means when you overlay it over the old image, you have a nice even transition instead of hard lines.
Ok, so what if we did lay the new layer over the old? Nothing would be different yet; we haven’t DONE anything to the old layer.
BUT! What if we brightened up the old layer using the Exposure tool? The underlayer here has been brightened by two full stops! Look at the blown out areas!
Not so good, huh? But, that’s really about how bright the water looked to my eyes.
So, what do we do now? Easy, because we have only brightened the BOTTOM layer using the exposure tool, the top layer has remained the exact same exposure the camera wanted to begin with: the brights aren’t brightened by what we did to the lowlights!
Here’s what the two layers look like combined:
Now all that is left is to merge the two layers by going to Layer/Flatten Image. Once we have a single JPEG image again, you can do your normal Leveling or Curving to color-correct and sharpen, etc.
Thus, here’s the original image and the final image together:
Or, if you prefer a bigger view, the final image:
See how the process works? Here’s another before/after:
Thus, as you can see, there is certainly a place for High Dynamic Range techniques in ordinary photography.
Pretty nice Zach. You can really see the impact in the second image.
As maddening as PS is to learn, theres no disputing its value. With similiar problem shots I’ve been trying a more basic appoach of selecting the darks using the magic wand on the blacks and then an adjustment layer to lighten them with either the curves slider or with the shadows/highlights slider. When Im more comforatable with selections and layers I’m going to have to try this approach as well.
COOL. I love seeing how different people do the same ideas differently in photoshop. It just opens up another direction or option on how to do things.
The program is so deep. there is usually 3 ways to skin the same cat.
I would have opened up the details in Camera RAW then went from there. I do that color correction by eye because I’ve been doing it daily for so long – (I do not recommend doing it by eye – I also know MY computer better than most), then i would correct the curves mathematically with the dark, mid and white point.
This gives me a different direction to turn. And helps as a great training tool. Thanks
The Camera Raw way is really quick but it can screw up color if you do to much. That was why I thought this was a great Idea to have your way as a backup and for training my folks here.
In CS3, When you open a RGB Jpeg or Tif, select camera RAW instead of the usual
I went to an advanced photoshop class a couple of months ago and we went around the room and talked about our skill level within the program. We had to choose from advanced, intermediate and beginner. I chose intermediate when the guy came to me, then he asked how long I had been using the program. I said about 18 years. He replied “18 years and think of yourself as an intermediate user?”
I told him I learn something new about the program daily. When that learning curve changes from daily to weekly – The I would be an advanced intermediate user. Learning something new Monthly almost puts me in the advanced category. Yearly would almost be a Zen State.
Forums like this keep me in that intermediate state. I like that.
Just a note on ACR and further to what Kevin mentioned.
If you hold the ALT (pc) key down, while you click on any of “Exposure/Recovery/Blacks” sliders you see a screen thats similiar to a layer mask. For example, an image that had no clipping (clipped blacks or blown highlights) would be entirely white (if checking blacks) and black (if checking exposure or recovery). As you move any of those sliders, the moment a single pixel is lost it appears on screen or the moment a single pixel containing data is “recovered” it dissapears off screen.
Meaning if you load an image in ACR (preferably raw) you have 3 methods of both correcting and seeing lost data.
1) The Histogram
2) The triangles located above the 0 and 255 points on the Histogram
3) Holding “ALT” while clicking on any of the exposure controls.The “recovery” slider corrects blown highlights and the fill slider corrects shadows.
You have to play around with it but if you had an image that could use a bit more exposure or some fill.
You can hold the alt key while sliding the exposure to the right a bit pushing the histgram to the right. The moment some pixels get “lost” they appear at which point you back off a bit. Or assuming you prefer the added the exposure, you can then hold alt/click recovery and move the slider a hair to the right and the blown pixels due to the added exposure “dissapear”.Conversely if your trying to recover some detail in the shadows hold the alt key while
1) increasing exposure ( lost pixels which show start dissapearing)
2) decrease the “blacks” ( blown pixels start dissapearing)
3) Add some fill
If you go too far on any adjustment and start clipping some they start appearing.And so on. Its a great way to see pixels that are lost/being recovered and when to stop thats a bit more powerful than the histogram or triangles which only alert you to the presence of blown pixels on one side or the other…Not where, how much, nor as fine in seeing the adjustments.
Cool!!! More control – Alt or Option Key on the MAC.
This is why I mentioned the something new everyday. This program… Man. I dream in Illustrator and InDesign but I dream “about” Photoshop
The recovery features in Aperture are good at recovering data in the shadows and highlights of a RAW file. The new 2.0 Beta of lightroom is out and I believe it has similar features as well. The fix in either would be faster than Photoshop.
Great stuff guys.
Love the final image Zach, it would be great to see more and more images like this in fly fishing. Like Kevin said, there are many ways to skin a cat and your process is actually more along the lines of what is called “Exposure Blending”. As you know, HDR requires multiple pics and is most often fully automated. The the process, that you did, is done in layers with just the one original pic, great method of correcting the camera to what your eye saw. I love this process myself as it really does put more reality back into an image that a camera simply cannot process in a sensor.
Kevin, are you a member of NAPP? It really is a great org for both Graphic Designers and Professional Photographers. They also have weekly training video’s that teach some of the newer developing techniques using CS3. I have been a member for a little over a year and have learned so much from there as well as made many contacts around the globe.
Ben,
NAPP is a great organization but I am not presently not a member but I was up to last year. My boss doesnt see the need for the “trainer to be trained” and he will not pay for my membership. I know that I should want to grow and learn but I dropped my membership to prove a point to him – he should invest a little staff training (plus I was a little preoccupied this past year)
I have also been thinking about changing my career, but that is another story altogether. (unless you know someone in North Atlanta hiring)
I do believe that ALL Photoshop Professionals should be a member or have a member of NAPP on their team – It is some of the best money spent. If no NAPP – I can justify spending time on the IA board at work because of threads like this one. Thanks Everyone… Keep the good threads coming.
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