How can I accurately photograph an empty picture frame?

Question

I'm doing an art project that requires me to shoot an object behind an empty wooden frame suspended from the ceiling. I wear glasses and when I look through the viewer it looks straight however in my computer it's clear that the perspectives are off; left side is wider than right side, or the top is wider than bottom.

I know there is an easy answer. I just can't figure what is and what I'm doing wrong. I can see the perspective change in my viewer as I move my camera up and down or side to side. But, once I think I've got it dialed in, I look at the image in my computer and I can see it's not.

Answer 1

Do note that what you see in the viewfinder isn't exactly what shows up on the picture. Many viewfinders don't show all of the field of view in the viewfinder, so if you are trying to frame a specific shot, you will most likely need to capture a slightly wider image, then distort, rotate, and crop the photo in post. You can do this by taking the shot from farther away, but keeping the zoom in the same place. This can be much quicker than spending lots of time moving your shooting position and angle fractions of an inch to achieve a more desirable photo.

But, to get the best end product, you should start with the best setup. Use a tripod with a quality head to allow for smooth, small adjustments. This will get you into the ballpark.

Too short of a focal length (lower number) can give distortion around the perimeter and amplify the perspective error you are seeing, and make your rectangular frame appear to bulge out (more pronounced with shorter focal lengths closer to fisheye lenses) However, your specific shot may require a specific perspective and may limit your options.

Answer 2

Normally, I'm in the get it right in camera camp, but in this case, I might try doing it as two separate images and combining them in Photoshop/GIMP/Editor of choice.

Then you would have the artistic freedom to place the object where ever in the frame looks best (think rule of thirds), also I can imagine that depending upon the lighting setup, the frame may cast a shadow upon the object, and doing it as a composite shot eliminates this. You probably will want to keep the lighting similar in the two shots to eliminate having shadows on the frame going a different direction than the shadows on the object..

Answer 3

There's a concept called "viewfinder coverage" and it is normally specified as a percentage. It refers to the fact that a DSLR's viewfinder does not show you everything that will be projected onto the sensor once you take the photo. This is normal.

Presumably, SLR manufacturers make the viewfinder's field of view smaller than the sensor's so that they can guarantee that everything you compose in the frame will be in the final image without having to precisely align the viewfinder. This saves them money.

Of course, what's not in the final image is important too, and for such knowledge there is a price. The Nikon D7000 is the cheapest DSLR I know of that features a perfectly aligned "100%" viewfinder. Last time I checked, Canon had no crop sensor DSLR with 100% coverage.

You can either get to know your particular camera's viewfinder coverage (i.e. exactly how much extra coverage there will be in the final image on all four sides, and whether or not the viewfinder is rotationally out of alignment), compose using the camera's LCD, or edit your photos after the fact.