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Tone mapping a single image: RAW or TIFF? A comparison.

Friday, September 11th, 2009

In hindsight this seems like a no-brainer, but since its come up in a few threads recently (e.g. http://www.naturescapes.net/phpBB3/viewtopic.php?f=2&t=162031 ), I thought I would address the question of whether its better to feed a TIFF or RAW file into Photomatix for HDR generation. For this comparison, I chose to tone map only one image, not several. Although you probably already know the outcome, the end images are only subtly different, but getting there was quite different.

I started with a base image, shot in Zion National Park last weekend:

This is the RAW image; all I did before feeding it into Photomatix was adjust the white balance to “shady” in DPP. The TIFF image looked identical; all I did was save it as an uncompressed TIFF with no other change. As soon as I opened the RAW image in Photomatix, it underwent a process of demosaicing and decompressing. I could already tell that it would be taking advantage of the “extra” info in the RAW image. It opened the image as a “pseudo-HDR” image, and I was able to obtain some stats on it:

The TIFF image opened simply as the TIFF image, and there was no more information associated with it than with a regular image. I first tonemapped the images using the Details Enhancer algorithm, and saved them as TIFF files for use in PS. There wasn’t much difference between the two:

Here’s the RAW file tone mapped with DE:

And the TIFF file tone mapped with DE:

Then I did the same thing using the Tone Compressor algorithm:

The RAW file:

And the TIFF file:

Whoa! I can only assume this funky-looking image is the result of the loss of information during conversion from RAW to TIFF early in my workflow. So, now I have 2 tone mapped images obtained from the original RAW file, and 2 from the original TIFF file. My workflow for each of the 2 final images was slightly different although not much:

For the RAW-derived images I used the DE tone mapped image as the base image in PS, and pasted the TC image over it. I used the Overlay blending mode at ~30% opacity, and the image looked pretty good. I did levels and curves adjustments (and also a desaturation of about -15), noise reduction with Imagenomic Noiseware, then some sharpening and I called it good:

For the TIFF-derived images, I again used the DE tone mapped image as the base image, and pasted the TC image over it. This time, because of the extreme nature of the TC image, I used a “Linear Burn” blending mode at about 25% opacity, and the image looked pretty natural. After normal processing (including noise reduction), here is what I got:

In the end the differences between the images are subtle, and I like them both for different reasons. The RAW-derived image looks more “natural”, but I sort of like the reddish “glow” that’s present in the TIFF derived image. The no-brainer here is that you certainly lose a lot of valuable information by using TIFF instead of RAW for this sort of application.

I doubt anyone cares as much as I do (haha), but this was an instructive exercise to go through.

Posted in General, hdr, national park, technical, technique, utah | 1 Response »
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Shooting wildlife: some tips revisited

Wednesday, August 12th, 2009

Last week, Juan Pons gave some great wildlife photography tips on the Outdoor Photo Gear blog.  If you’re just getting started in wildlife photography, these tips will be invaluable to you.

However, as I was reminded the other night, even if you’ve been doing this a while, these tips will be invaluable to you!

As I last blogged about, there are some fantastic nighttime wildlife photography opportunities out there, if you know where to look.  However, because you’re fumbling around in the dark, its important to keep tabs on your gear.  When we were shooting kangaroo rats the other night, I found that I could use a little more light:

While this image is pretty good, I wanted a little more light on the scene.  So, I set my flash to give just a little more “oomph”.  Despite my adjustments, my next shot looked like this:

DPP07D9080A0D1915

Wait…what?!?  I set my flash to give 2/3 stop MORE light–not less!  What happened?  Well, after I made my adjustment, I was futzing with the spotlight and other things, and I accidentally twisted my thumb wheel, inadvertently changing my aperture from f/8 to f/16!!

While my mistake wasn’t disastrous to the whole evening, something tiny like this could easily ruin a once-in-a-lifetime shot.  So, Juan’s advice is sound: check your camera’s settings often.  It just might make the difference between an awesome shot, and one you will eternally kick yourself for.

After resetting my aperture to f/8, my adjustments seem to have worked:

Sweet!  Much better.  Thanks for the gentle reminder, Juan.

I would also add a 6th point to Juan’s list: try new things.  If you have the opportunity, try shooting your subject at more than one aperture or exposure–you might be glad to have the options back home at your computer!

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Seeking the creatures of the night

Monday, August 10th, 2009

If you’ve done much photography/camping/hiking/being outside at all, you’ve surely heard all of the nocturnal critters starting their nightly rounds shortly after the sun goes down.  Have you ever wondered who is out there?  Seeing them isn’t all that hard, but photographing them can be a little challenging, and often downright hilarious!

Last night, a friend and I went to the University of California’s Motte-Rimrock Reserve, near where we live.  The Motte is prime habitat for Stephen’s kangaroo rats, Dipodomys stephensi.  However, life for kangaroo rats is hard: they have to contend with rattlesnakes, owls (both great-horned and barn) as well as photographers with big cameras trying to take their picture!

Our method was pretty simple.  We scattered a little bird seed near the rats’ burrows and waited for them to find it once the sun went down.  It didn’t take long; within about 20 minutes after dark, “k-rats” were bombing the bird seed from the safety of their burrow.  Seated about 20 feet away, my friend and I waited with a bright flashlight and our cameras.  

Once a rat was comfortable with our presence, one of us would spotlight it, and the other one used the light to autofocus on the rat, and fired:

Stephen’s kangaroo rat, 2009

Its not too bad of a system to take turns doing this, and doesn’t take a lot of extra equipment.  I shot my frames at f/8, ~1/60 of a second–it doesn’t really matter though because the flash will freeze the action.  

After you get bored with the k-rats, its nice to look for other critters.  While owls were flying around, they weren’t being conducive to being photographed.  But, like I said, there are other creatures who seek k-rats.  Locally we have a fairly large population of red diamond rattlesnakes (Crotalus ruber).  

We found this fellow curled up alongside the dirt road, about 20 feet from us.  It was clearly waiting for a meal:

Red diamond rattlesnake, 2008

The snake was very compliant, and gave us about 15 minutes to photograph it before it had had enough, and slithered back into the bushes.

After appreciating the creatures of the night, we headed home, allowing them to resume their nightly routine.  Its always nice to experience new wildlife, it is important to make your impact as little as possible.  No photograph is worth endangering an animal.

So, get out there and look at your favorite wilderness area in a whole new “light”!

 

Posted in california, locations, technical | 2 Responses »
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High Dynamic Range photography, part II: fixing the halo

Tuesday, August 4th, 2009

Yesterday, I outlined one of the biggest problems with HDR photography I’ve encountered since venturing down that road a couple of months ago: the dreaded halo.  The “fix” of getting around it is surprisingly simple, and I’ll walk you through it with an image I recently edited:

Sunrise, Joshua Tree National Park, California, January 2009

This is a 3-shot HDR that I processed just last week, after getting the courage to try HDR.  You might be asking why I’m not following through on the image I showed you yesterday.  Well, in the interest of full disclosure, I still haven’t processed it.  However, I will follow the same workflow on that image as for this one. 

I won’t post the source images, but I will post the tone mapped images.  For my workflow, I generally follow Royce Howland’s suggested settings  for both the DE and TC methods of tone mapping.  With that said, here is the image tone mapped using the DE algorithm:

jtree_DEtonemapped

There is some lens flare that I’ll later clone out, but do you see the halo around the joshua tree?  That light purple line all the way around the whole thing?  That’s what we want to get rid of.  Other than that, this image doesn’t look too bad; its lacking some midtone contrast, which is also characteristic of the DE tone mapping algorithm in Photomatix.

Now let’s look at the other tone mapped image, the one done using the TC algorithm:

jtree_TCtonemapped

What do you see?  First you see that its very contrasty–almost too contrasty–especially compared to the other tone mapped image.  However, what you don’t see is the halo!  The TC tone mapping algorithm does not give you a halo.  Good.  Now, we can open these two images in Photoshop and pick apart the best of both tone mapping methods.

I like to use the DE tone mapped image as my base image, and I copy and paste the TC image over the top of it.  The next step–the crux of this workflow–is to choose a blending mode for the TC layer that–at least mostly–eliminated the halo in the DC image.  I’ve had pretty good luck with Overlay, Color Burn, and Linear Burn, but probably the most success in Overlay.  Overlay multiplies the dark areas and screens the light areas, and logically would be good for eliminating the halo.  

Once you’ve settled upon a blending mode that looks more or less “natural”, you will need to adjust the opacity slider to make it look even better.  On this image, I settled for 35% opacity.  

I hate to be anticlimactic, but once you’re done blending these two layers, you’re pretty much done and can edit the image like normal.  There was a little halo still left at the top of the joshua tree, so I selected the inverse of the tree and just closed the sky to look less halo-ish.   In addition, I cloned out some lens flare, and applied noise reduction (I use Imagenomic’s Noiseware).  Other than sharpening and levels/curves I didn’t do much to it.  One thing I’ve found is that I don’t have to apply much saturation to HDR images–they look pretty good as is.

I hope that this has been helpful, and that you find it useful.  I’d love to hear feedback as you try this method with your own images!

Posted in california, hdr, national park, technical | No Responses »
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High Dynamic Range photography, part I

Monday, August 3rd, 2009

Although its been popular for a while, I’ve recently begun working with multiple images to produce high dynamic range (HDR) photographs.  What is HDR?  HDR is a series of methods developed to produce a high dynamic range image from a set of photographs taken with a range of exposures.  There are multiple methods for producing an HDR image, from blending multiple shots in Photoshop to processing a single RAW image multiple times and blending those in Photoshop to using HDR software like Photomatix.

My goal here isn’t to tell you how to make an HDR photograph, because there are already fantastic tutorials out there, written by people much more talented than I am.  Probably the most complete tutorial was written by Royce Howland over at Naturescapes.net.

Because you can probably already produce an HDR image on your own, I want to share some nuances of the process I’ve learned to make your images look more realistic.  These aren’t new techniques, and I didn’t come up with all of them myself–to give credit where credit is due, Royce Howland, E.J. Peiker and Paul Stoczylas are the masters.  I’m but a student.

Part I: Getting rid of the halo

Photomatix is a powerful program and has a very user-friendly interface that pretty much does the work of producing an HDR image for you.  Because there are no monitors that can visualize that kind of dynamic range in an image, you must first tone map the image before being able to display it.  You have two options: Details Enhancer (DE) and Tone Compressor (TC).  DE is the default, and although it lacks some mid-tone contrast, it looks a lot better than a straight TC image which is way over-saturated.

The problem with tone mapping with only one algorithm is that you’re limited by each one’s constraints.  For instance, halos are a big constraint of the DE algorithm:

Towers of the Virgin 2Towers of the Virgin, Zion National Park, Utah, June 2009

This shot looks pretty good, but you notice at the junction between the sky and the cliffs that the sky turns noticeably light blue–that’s because I only tone mapped with the DE algorithm.

This halo can be especially problematic in images where you have trees against the sky.  In this series of posts, I’ll cover a couple of methods I’ve learned to make the HDR image look a little more  realistic and squelch that halo!

Stay tuned…

Posted in hdr, Photoshop, technical | 2 Responses »
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