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- Beach shot 1
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- Beach shot 2
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- Beach shot 3
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- Beach shot 4
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- Beach shot 5
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- Beach shot 6
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- Beach shot “combined solution” using Photoshop
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- Beach shot “combined solution” using Photomatix
So, you’ve heard some folks talk about “high-dynamic range imagery” or HDR, and you think you sort of understand it, or not really? Well then, I hope to de-mystify it for you in a series of blogs.
In my previous blog, I talked (or more like bitched) about why cameras suck; and one of my reasons was that they lacked sufficient dynamic range in capturing light.
“…, let’s talk about dynamic range. This is the whole problem of the images above. We’re only stuck with 0-255 per RGB channels. This means that we need to describe the brightness of what we see — from dark shadows to sunlight — within the integer range of 0 to 255. Even RAWs don’t cover it since the dynamic range needed to describe what we see could be 0-1,000,000. Yes, cameras suck. There are high-dynamic range imagery, and I will talk more about that soon.”
As shown above, there are series of photos that describe this problem. In the beach shot 1, you see that the exposure was very long, so most pixels are washed out, but you can still see some contrast in the dark parts of the palm trees as well as the dark shadows on the sand ridges.
As the series of images get darker, e.g. beach shot 2 and beach shot 3, you can see the scenery much better, but the bright area around the sun is still too washed out. By beach shot 6, we can see some outline of the sun better but everything else is now too dark.
Somewhere in this series of variously-exposed images lies the “right” answer for the composite image — this is the dynamic range problem. Our eyes can see much better contrast than any of these camera shots (also because we can dynamically adapt better too, but that’s some other blog). You can imagine manually photoshopping these images to get the solution image you want. A more automated way is to create a single high-dynamic range image from this series of images, then tone map it.
Putting aside the technical lingo bullsh!t, I hope I’ve convinced you that there is a way to combine these images somehow to get the final image you want. (And I won’t bore you with the tech details either — if you must know, let me know pls.)
There are nice software products to do just this: Photoshop, Photomatix, and Enfuse. There are more, but these are the ones I like. (If you have your favorite, please comment and share!)
Beach shot "combined solution" using Photoshop
Beach shot "combined solution" using Photomatix
I’m not showing Enfuse just yet since it really isn’t HDR. But I’m gonna stop right here for now, since the blog is getting too long. I will talk more about Enfuse and more of HDRI-related issues in part 2 of this series.
July 22nd, 2009 at 10:37 am
Nice writeup. Is it just me, or do all Photomatix results look way overdone? The results clearly preserve the detail from all the exposures, but they don’t look at all like how my eyes would respond to the actual scene.
Yes, I know that photography isn’t always about perfectly capturing reality. But usually there’s a delicate balance between capturing reality and improving aesthetics. In my opinion, the Photomatix algorithm achieves neither.
Case in point: http://www.flickr.com/photos/msc72/423277477/
Barf. The only thing is missing is Photoshop lens flare.
July 22nd, 2009 at 10:53 am
Yes, I agree! I’m still a proponent of using Photomatix in a combined solution, but it only works as a SUBLE overlay of the Photoshop tone mapping. Otherwise, things start to look scary.
July 22nd, 2009 at 9:30 pm
“Barf.”
love it.
July 22nd, 2009 at 10:46 am
I agree with Mok, single-exposure images still need quite a bit of post-processing to look their best. Having worked extensively over the past 4 years with HDRI, I have learned that the best solution (to date) lies in the combination of exposures and other techniques.
If you tone map an HDRI file well in Photoshop, you will get a wonderful and realistic starting point for your image. Overlay that with a transparent tone mapping from Photomatix, and you will get a beautiful range of colors and tonality. You can see a hint of this in the Yellows of the sky and the crystal blue water of the Photomatix image above. Occasionally, you will need to manually mask in a window that is over-exposed, or a distant room that is just too dark. Also, you may find yourself running into situations where there are multiple light sources, requiring an HDRI file with both multiple exposures and multiple white balances.
Phew.
I haven’t even mentioned RAW format yet! If you have not used the proper exposures or white balances when taking the photos, even HDRI has issues. This is where RAW format can be helpful. Photoshop has a wonderful dialogue where you can adjust all of the original camera settings very effectively.
The only thing that I haven’t seen yet is a way to correct focus.
So, this can get quite technical. Going back to one of Mok’s older posts, cameras still have a long way to go!
July 22nd, 2009 at 9:32 pm
Thanks, Robyn! Do you have examples that I can post up? Would be great for the readers, if you have any.
Tx for sharing!
July 22nd, 2009 at 5:04 pm
I think one of the fundamental issues concerning fidelity of dynamic range and static panoramas is the focal point. A panorama strives to have “omnifocus” <– made up word. A surveying human eye always has a specific focal point, constantly adapting, such as "re-scaling" dynamic range depending on focal point (like trying to make out the details of an underexposed area of the panorama). For high fidelity immersion, we need to get into focal point tracking with visuals that adapt to that. The other option is to bring the entire static visual to a point where it maxes out perceived dynamic range, which I guess is one of the impetus behind HDR imaging. The problem with the latter approach is that realism is compromised because it appears surreal. I personally find HDR to be an acceptable compromise though.
July 22nd, 2009 at 8:52 pm
I’ve tried several times, but tone mapping is too difficult for me. The images I made was not good.
I am looking forward to next post.
July 23rd, 2009 at 7:28 pm
Sure thing! I will share what I think is a good solution. Thanks for sharing.
July 23rd, 2009 at 10:08 am
Nice article on HDR. I’ve been wanting to try to create some HDR images, but lack the tools and the time.
What criteria do you use to find “..the “right” answer for the composite image..”? Is this more of an artistic answer or a technical one?
July 23rd, 2009 at 7:32 pm
Good question. For me, it’s more artistic than technical, but can be argued either way.
One way to define what’s “good” could be trying to replicate what we see. But even that depends on people’s eyes, shapes, acuity, age, etc.
But there are folks like Ansel Adams who used hard-core dodging/burning (manually without photoshop! yikes!) who created surreal and awesome sh!t. Pure visual genius. Almost impossible to quantify this..
July 23rd, 2009 at 7:33 pm
BTW, good to connect again, DDay!
July 23rd, 2009 at 9:46 pm
[...] This blog is the second part of the previous blog on high dynamic range imagery. [...]
March 20th, 2010 at 1:17 pm
I think photo number three is the most pleasing,,, the photomatix one is barfy