Monday, March 3, 2008

Digiscoping: Post-processing - Workflow

Workflow Workflow is a very personal subject to photographers and it is constantly changing. My earlier workflow for processing images involved adjusting for brightness/contrast, color balance, cropping (if necessary), selective enhancement, selective cloning, sharpening and noise reduction.  I would process my subject and backgrounds differently to make the bird 'pop' more, but today's cameras are making this step more obsolete.  Here are some suggestions for improving image quality from your digiscoping camera(s):

Adjust brightness/contrast You can compensate for an underexposed image but you can’t compensate for an overexposed image. So always make sure that your images don’t contain too many blown highlights (or saturated whites). On my cameras I adjust EV to –1/3 to –1 depending upon how much white is in my bird. We can adjust brightness/contrast 2 ways: either by using the brightness/contrast sliding bars in our package, or by using ‘Curves’ adjustment. Curves is great because you can control tonal changes in brightness and contrast better than you can with just a linear adjustment. Be careful, however, to avoid blown highlights!  

Adjust color balance - 'lose the blues' By adjusting individual red, green and blue channels we can remove the overall blue cast to the image and give it a more natural color.

Crop to remove vignetting Crop that portion of the image where shadows are a problem or to place your subject using the rule of thirds. If your software doesn’t have a crop tool, highlight the portion of the image that isn’t shadowed and copy and paste into a new file.

Selective enhancement Let’s enhance those eyes a touch! When digiscoping always concentrate on the eyes. An eye in focus means your bird is in focus. In some cases, like this owl, a slight brightness/contrast adjustment to the eyes will really bring out their best feature. 

Selective cloning We’ve got a nice image to this point, but the black spots to the left of the owl and the twig to its right are a bit of distraction. We can remove those distractions with a bit of cloning. Now, before going on, let me assure you that I’m well aware of what image altering can do to the scientific validity of an image, and that its important to be aware of the science vs. art argument when it comes to things like cloning and image adjustment. As long as you let people know what you did with an image when you post it hopefully there’ll be less argument whether the image is considered real or not. Its another reason why the original digital file should never be altered… Cloning is a tool that allows the user to copy a portion of the background and paste-over or clone a bit of the foreground to remove distracting elements. You can select how big of an area you want to copy and where you want to copy it from and literally smear it over the offending twig or black spot. When used properly the final image shows no evidence of the cloning operation. Improperly used, however, the clone itself becomes a distraction.

Selective sharpening and noise reduction The CCD’s (charge-coupled devices) in compact digital cameras are quite small and prone to noise, especially under cloudy conditions and at higher ISO settings. Thus, noise reduction is an important part of every image package. There are several software packages available dedicated solely to noise reduction and have received favorable reviews by users: Imagenomic Noiseware 2.5 and Noise Ninja. If you don’t have software package available, you can apply selective smoothing or blurring to images to remove noise. In Photoshop this would be termed Gaussian Blur. My workflow for noise removal is the following: - highlight subject, apply light blur followed by sharpening - highlight background, apply more blur Photoshop has a ‘magnetic lasso’ tool that allows you to freehand draw a line that will snap to the nearest sharp edge (bird’s body). A line 1-pixel thick will allow you to highlight the bird or part of the image of interest. Then apply a Gaussian blur (or smoothing) to the highlighted subject (I use 0.5 pixel) to remove some of the pixel-effect before applying any sharpening. Otherwise, sharpening will only increase the amount of noise in the highlighted subject. Now apply a sharpening filter to bring a bit of snap to the subject (in Photoshop I use the Unsharpen Filter – Amount=75%, Radius=3.0 pixel, and Threshold=0) that allows a bit more control over the amount of sharpening to the image. Avoid too much sharpening – this leads to higher contrast that leads to loss of detail, more noise, and even a halo-effect that looks un-natural. To process the background, Photoshop has a Select\Inverse function that will now highlight everything ‘except’ the subject. Now we can apply a bit more Gaussian blur or smoothing to give more noise removal to the background. And that’s it! Here is our image before and after post-processing.


A note about color fringing We talked about chromatic aberration in scopes and in camera lenses. We can remove some of that purple halo around the bird by de-saturating the ‘blue’ color channel. In Photoshop select \Image\Adjust\Hue/Saturation and de-saturate the color blue until the halo disappears. This will also give the image a more natural color overall.

Add a copyright symbol? – [Alt][0169] = © A copyright symbol added to a web-posted image will not prevent others from stealing your images, but it will make it more difficult for someone to take credit for your work. Use the number keypad on the right side of the keyboard to make a copyright symbol. Hold down the [Alt] key and type 0169 on the right keypad and release the [Alt] key.


Dale Forbes said...

this is another great blog post - seems I missed it last year when you originally posted it. it certainly pays to come by here every now and again and wander about to see what I can see...

Nelson said...

Jerry- I understand your presentation- however, the more you digiscpoe, or even spend most of your time birding observing through binos, or a scope, the more you are setting limits on what is out there to be observed.
I am talking specifically of hawk watching. You will never understand that Northern goshawks are moving into cities and suburbs, and have been doing so for many years. This raptor is usually always observed in the sky, and very seldom perched, is one of the most exciting raptors to observe.I have 16 years of continuous observations of goshawks while living in Southern CA, Coastal Washington, many areas of East Texas, and many areas of Southern AZ. I will try and adapt my scope and camera to a shoulder stock and try and garner some verification photos of Northern goshawks. Nelson Briefer - Goshawk specialist- Tucson and Anacortes, WA.