Thursday, March 6, 2008

Digiscoping: Cameras - Settings

Settings Camera settings can make or break a day out in the field digiscoping. First thing to stress, is "know your camera" before you get out into the field. I learned this the hard way during our 2005 CBC in Monroe, MI. It was -25ºF w/ windchills to -40ºF on Lake Erie and we had just spotted a Willet on the shore of Lake Erie on December 17th. This was a state record CBC bird and we needed to document it. I had a brand new Canon A620 Powershot that I was using for the first time, and thought I could get away with using the same settings that I had used w/ my Coolpix 990. Wrong. I had set the camera to shutter priority (1/250 sec.) and thought that the camera would adjust aperture to compensate. Unfortunately I didn't know that that the aperture limit on the camera was f/8, so in the bright, freezing sunlight all but one picture came out badly overexposed. We were lucky to get enough shots to record the Willet, but I learned my lesson the hard way! Trying to figure out why images were overexposed w/ frozen fingers while kneeling in ice-cold water is not a good time. There's been much discussion of what the best settings are, and opinions vary. So, I'm suggesting the following settings for first-time digiscopers based on my experiences and logic: -

Aperture priority - Today's cameras can be aperture limited (f/2.8 - f/8), so set the camera for 'A'perture-priority and let the camera select shutter speed. Rule of thumb for any camera for digiscoping is "Set the Aperture to its largest aperture possible".  For example, if you have a lens that allow f/2.8, then shoot at f/2.8.  This will give you the fastest shutter speeds possible and the most correct exposures.  Stopping down to smaller apertures (f/5.6 - f/16) will not improve depth of field, and will generally cause the camera to overexpose, because the scope itself has a fixed aperture of approximately f/8.  If you have to shoot less than 1/125 sec. then know where your ISO select button is and bump up the ISO. Otherwise, set the self-timer and pray your subject remains still long enough to get a decent exposure. Shoot at the lowest ISO possible (100) as higher ISO settings on small compact sensors will produce sharper, but noisier images.

White balance – Auto Compact cameras do a pretty good job at adjusting white balance for specific lighting: sunlight, shade, clouds, or if indoors - fluorescent or incandescent lights. Use 'Auto' - its one less detail to worry about, and white balance can be adjusted w/ post-processing by adjusting color balance. If you shoot RAW you'll be able to adjust WB during post-processing.

Metering – Center-weighted vs. Spot. Always a tough decision, but I use Center-weighting because it allows the camera to adjust exposure based on my subject's lighting (and sometimes part of the surroundings). A perfect example is digiscoping the moon - the bright globe will be horribly overexposed using the camera by itself, but because the scope magnifies the moon to almost full screen the camera will expose on the moon itself and not on the black background.

Exposure Compensation [+/-] = -0.3 to -0.7 If my subject is white, I may then need to underexpose an additional -1 to -2 stops, so know where the [+/-] Exposure Compensation button is at all times. On sunny days I shoot at -0.7 and as much as -1.0. This will help avoid blown highlights and give up to a full stop faster shutter speed. If set too low then images will be severely underexposed and noisy! On overcast days expect to use 0.0 to +1.0 so that your subject is not a dark silhouette against a bright sky background.

AF Mode - Single vs. Continuous.  I've learned that Single AF is the best option to use, especially for the Nikon V1.  With the EVF I can fine-tune focus after the camera finds initial focus w/ AF/S.  With the camera on AF/C the camera is constantly trying to refocus, especially when I've adjusted focus w/ the scope. Sometimes you'll need to fine-tune focus using the scope even when the focus-box on the camera is locked-in.

Single vs Continuous exposure. I shoot Continuous always! Birds are always moving and shooting two or more frames in a burst will increase my chances of getting a sharp image, or capture that special moment or pose. The Canon A620 was great in that it allowed continuous shooting as long as there was space on the memory card. The F30 only allowed first-3 or final-3 shooting so I was limited to 3-frame bursts. The Coolpix P5000 only allows 0.8 fps, and is much maligned as a result. I, however, like the focusing and color balance so much its worth it. The Nikon V1 shoots 10 fps, and up to 60 fps, so the keeper rate has gone way up!

Image stabilization – may work for hand-held The newest cameras have image stabilization and it seems to work for digiscopers. I can't comment on its merits for digiscoping, so try it out.

Image adjustment – Normal All cameras allow for in-camera sharpening, color saturation, etc. While very good, cameras that high sensor noise tend to overcompensate by applying too much smoothing to images. Best to leave Image Adjustment on Normal and correct for sharpening/noise/etc. using photo-editing software.

Saturation – Normal  My F30 had a Saturation setting that allowed for Chrome or saturated colors in my images. For most applications, leave on Normal and adjust for color using photo-editing software.

Sharpening – Normal Same with sharpening. Cameras can oversharpen an image and add more noise than can be corrected afterward with software. Leave on normal and sharpen afterward with software. Some recommend sharpening images as the last step in image-processing. I do it before I downsize an image so that the subject appears more normal. Sharpening after downsizing an image file increases the chances of a pixel-effect (blotchy squares along the edges of the bird).

RAW vs. TIFF vs. JPG – FINE Always shoot at the highest resolution possible! That said, there is a trade-off between resolution and the number of images that can be stored on a memory card. It also takes longer for the camera to write big files. RAW and TIFF will give the highest resolution images, but at a cost of memory and camera lag between shots. I  used to shoot at JPG FINE since the files had the least amount of compression applied to them and it reduced camera lag. None of my cameras had RAW or TIFF capabilities, however, so I recommend comparing your image quality before deciding. With RAW you have the ability to adjust exposure after the fact, and this can help save images w/ blown highlights.  But you might see slower write speeds w/ your camera.  Shoot the same subject using the various image types: RAW, TIFF, JPG-FINE and compare quality after blowing the images up to 200-300%.

Size – largest possible See previous discussion. -

Focus Confirmation – valuable! The A620 shows a green box around the subject when its in focus, and a yellow box when its not. I've come to trust this focus confirmation to the point that I won't shoot unless the green box is showing. I get more keepers this way. If your camera has focus confirmation, trust it over your eyes, at least until you're convinced otherwise. Especially when its too sunny to see the camera viewfinder you can at least rely on the focus confirmation. With the Nikon V1 the shutter won't fire unless the focus box is green!

Focus – Macro vs. Infinity vs. Autofocus This is tough one. Up front I'll say that I use Autofocus all the time. Macro focus is great in that the focusing range is shortened, and thus quicker for locking in on a bird. However, unless the bird is the closest subject to your scope, the camera will focus on the twig or leaf in front of the subject and the bird will be out of focus. Infinity focus works well in that you can use your scope to focus the bird 'manually', but camera viewfinders aren't always bright/clear/sharp enough to see whether the bird is truly in focus. I always make sure that the bird is in focus with the eyepiece, then I'll attach the camera and let it autofocus on the subject.

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