Picnic on the Poudre (+ Photoshop Tip)

This is an image from Picnic Rock park on the Cache La Poudre River northwest of Fort Collins. I took it on a late afternoon in June (the water level was quite high back then). Since this is located near the bottom of the canyon, the rocks get their last light a little more than an hour earlier than actual sunset at this time of year. Previously, I hadn't seen many images of this cool spot on one of the nation's "Wild and Scenic Rivers" and now I know why. Getting a shot of both canyon and river is not as easy as it may seem.

This image was difficult for a variety of reasons. Obviously, the dynamic range (even after using GNDs and some weak fill flash on the foreground tree I still had to make some shadow/highlight adjustments) as well as the need for stitching to depict this entire sweeping scene. Wide angle lens + weirdly bending river + a very small, muddy place to stand while capturing the images + pano stitching = a lot of potential problems. See below.

In post processing, after stitching 7 images (that were taken with lots of overlap and weren't quite 100% level due to the muddy ground and a sinking tripod) together in Photoshop's photomerge I could tell the resulting distortion and funky horizon line was going to be a challenge to work with. Photoshop's popular "lens correction" filter was just not up to the task since the horizon was curved somewhere other than the center of the photo and it tended to stretch the pixels on the image corners too much in this case. After much trial and error I found a seldom-used (at least by me up to this point) PS filter that saved the day. My process is detailed below:

- Step 1, expand the canvas size (image-> canvas size) to give yourself a several inches of buffer space around the photo. The bigger the bend you want to correct, the bigger the extra frame you'll need so you may have to come back to this step if you find you don't have enough space in Step 3 below.
- Step 2, if the photo is horizontal you'll need to rotate it to a vertical. Image-> Image Rotation -> 90 CW or CCW.
- Step 3, go to filter -> distort -> shear... You'll see a grid with a black vertical line in the middle. (filter depicted in screenshot below). Click on the line on a place that roughly corresponds to the location of the top of the curve you want to correct in your photo. A black dot data point will appear similar to if you were using curves to change the brightness/contrast. Hold down the mouse on the point and pull in one direction or the other and watch in the preview window what happens to the horizon. The correction is pretty sensitive so you won't likely need to pull the line very far to equal a lot of movement. You can also move the point up and down the line or add more data points if you have other parts of the image to correct. You may have to play around with this for a while to get the desired effect. Also, you can use the rectangular marquee or other selection tool to only select a certain part of the image to correct before using this filter.
-- If in step 3 you see the image is wrapping around to the other side - perhaps the sky is appearing under the ground or vice versa - you're going to need more canvas space as mentioned above.--
- Step 4, rotate back to horizontal. (corrected image shown below) You can check using PS's rulers or guides how level the horizon appears and whether more correction is necessary.

Screenshot of the Sheer filter.

As you can see the river's horizon seems straighter and a bit more easy on the eyes. On this image I still had to do the process a couple more times for fine tuning the horizon line before the final crop but I think the time was worth it and really improved the final image. That is why I wanted to share this process with you, especially if you do a lot of pano stitches.

So far, I've only done this for straightening difficult off-center horizons, but I can see this filter has much untapped potential and can possibly be used for some tilt/shift and movements-types of applications too. It's not necessarily a perfect subsitute for a TS/PC lens or a large format setup, but it's a cool "digital tilt/shift" solution. The trick is not to go overboard, the adjustments are touchy and if taken too far can severely warp the image's pixels. Have fun experimenting on your own images and post your results!

Frankly, Josh, I wouldn't have even bothered to "fix" the shoreline. It's not obvious that it's unnaturally curved (if indeed it is), and the fix presents a new set of problems. But you've done an admirable job, and it's nice to know about that filter, which I'd never heard of before. It's a beauty of a shot that I would actually like a little better if the shadow/highlight and saturation in the final were somewhere between your finished photo and the more original look of the work-in-process versions.

Pretty cool Josh, thanks for sharing the tip!

Thanks guys. Above is a happy-medium of contrast, shadows, saturation and sharpening between the two versions of the photo. Good to know the shadow areas are sufficiently bright Todd, I was still wondering if they were too dark even on the version of the first post.

I feel the image after the correction is a better representation of what I actually saw from this view: the far side of the river as relatively straight while the nearer side was curved. The rocks also just seemed extremely skewed to me in the version immediately after the PS's auto merging. Normally, I wouldn't stretch a photo out of it's proportions (yes, that can lead to the other problems Todd hinted at above), but this technique ended up being far less damaging than the "lens correction" filter. Don't get me wrong, the lens correction filter is a great tool that should probably be attempted first (especially in CS5 where you can even make auto corrections on individual exposures based on lens brands & models - very cool!) but, in this case, it didn't work very well with the pano stitch. "Shear" was probably intended more as a special effects filter which is why I wouldn't recommend it yet for a wide variety of uses and when it is used it should be done in a slight manner.

My thinking on the brightness (or lack thereof) of things like this goes like this: We often think we need total shadow detail, or big, looming moons in the sky, or photos of animals that would feel right at home in a trophy case instead of in a frame and hanging on the living room wall. Usually all we really need is a hint of that magic, and people will find things on their own – slightly less shadow detail, an appropriately sized moon cresting the horizon, or an animal surrounded by its natural environment. That's not to say you can't have it both ways, it's just an observation.

Beautiful Image, love the gold.

Great image and also thanks for the tip.

Cool image and tip!

Very nicely presented tip. Well done on the image and the processing.

Thanks for your great description of the processing. And I've never seen Picnic Rock so scenic.

Josh, I have seen this area many times (used ot live in Ft Collins) and you did a great job with this IMO. Also, thanks for the steps in your processing of this. I still have a lot to learn and new tips are always great!

Theres a million ways to skin a cat in PS--whatever works is the best rule. The key is how large you can print it without it looking like its been mangled. Nice shot, Josh!