My hobby is photo logging old cemeteries, but I am no longer able to squat down to align directly with the upright stones. How can this be done? I see "selfie sticks," but I wonder if such an extension is available for my use. I do not use a phone, but a regular digital camera. How would I focus if the camera is mounted on a stick several feet from me?
You can do perspective correction in post. This emulates the effect of tilt-shift lenses. Not all photo manipulation programs have this capability. I often even prefer perspective correction over changing the camera's position, because it allows me to make straight lines parallel while still keeping the angle of the photo that I want. For instance, you can take a picture from above, like this:
And you can correct the perspective to make the lines parallel:
This is a pretty sloppy job... you'll notice how it's a bit squashed, but it should give you an idea of what you can do.
The picture is still from above, so you have additional freedom to frame the picture (choose what goes in the background, for example).
You're not forced to use one-point perspective in the final result.
You have additional freedom to move the camera to account for things like reflections if you're taking pictures of something shiny.
You'll want to take a few extra pictures framed differently if you do it this way, at least until you get the hang of it. You may often need more space between the subject and the edge of the photo than you realize.
As for focus... without a tilt-shift lens or a large format camera, you're just going to have to use a smaller aperture.
Mount your camera on a low tripod and tether your camera to a laptop. You would then preview on the laptop before remotely triggering the shutter and capture the image through software like Aperture or Lightroom.
It's more stuff to lug around but you won't need to squat long to compose and capture.
You mention that you use "a regular digital camera", which a few Google searches suggest means point-and-shoot.
I hope I will not sound offensive, but maybe a flip screen camera could get the job done?
Of course the focus/etc will not be as great as with a DSLR, but if you use a regular digital camera in the first place, then it should be OK.
Lower your arms, take a picture while looking at the screen, then have a look and take again with different settings if the details can be improved. It will be as low as if crouching, and far less tiring.
UPDATE: As Raphael pointed out in the comments, there are also DSLRs with such a screen.
The Canon 70d has built-in WiFi that you can use to control the camera from a smartphone or tablet, via an app. You can mount the camera on a low tripod (or a taller tripod with an inverted centre column), see what it's pointing at in real time on your phone/tablet and control the shutter from it, too.
You'd still have to bend down to position the camera, of course, but I guess that would be easier on your legs than squatting.
I mention the 70d because it's the camera I have (though I've not used this feature of it); other recent cameras probably have similar features.
You can improve the perspective by simply standing back and zooming in. The further back you can go the closer to the correct perspective you'll get. You can then correct it further in software if need be.
You can also further improve the perspective by positioning the subject off-centre in the frame. You want it below the centre of the frame if you're above it. This will almost certainly mean you need to focus and recompose. That is you point the camera at the subject, half press the shutter so it locks focus, reframe the shot with the shutter still half pressed, and then push the shutter all the way down. You can then crop the image to remove the empty space above the subject. Of course the downside is that you end up with a somewhat lower resolution image.
How about using something like a Walkstool and a short tripod? http://www.walkstool.com/comfort
Does your digital camera have an articulating screen? You could use it like a waist-level finder.
Another option is to use a tilt-shift lens. Canon makes good ones, the Nikon ones aren't so great (I'm a Nikon user). This will enable you to take a photograph with the camera at eye height standing up with no converging vertical lines.
You didn't mention whether your camera is a DSLR or a compact camera, but if it's a DSLR with live view and a flip-out or articulating LCD panel, then there's an easy way, which I use all the time these days as my knees are too challenged to get down low very often.
Mount the camera on a tripod or monopod set to the height you need, turn on live view and flip out your screen (if it is an articulating one, so much the better), then simply lean over so that you can see the screen and work with it rather than the viewfinder. Use live view to focus if you're doing so manually (my camera allows for 5x and 10x zoom in live view - I usually find 5x is enough, using manual focus), and keep it in live view when you press the shutter (because using live view engages mirror lockup, which means no stray light will find its way through your viewfinder). Live view is battery hungry but I'd rather carry an extra battery than stress my knees all the time.
Some hiking sticks have a removable head. (Check at REI) Unscrewing the head reveals a tripod-socket-compatible 1/4 inch stud. I attach my camera to my stick to take a photo from a higher or lower perspective. When holding the camera lower, the camera and photo will be upside down. But, that's a one-button fix in most photo editing software.
To release the shutter, you can use the self-timer, or, if your camera has them, infrared or smart-phone remote controls.
I wouldn't worry too much about whether you can frame the shot on the screen or the viewfinder. Tombstones are easy targets. You can just look at the photo and take another one if it isn't composed exactly right.
Using the stick is faster than setting up a tripod for each photo. Often there is limited space in graveyards for a tripod, anyway. The stick is lighter than using a collapsed tripod for the same purpose.