There are optical properties which are inherent to the physical dimensions of a camera's sensor, because the lens focal length that is needed to give a particular field of view will depend upon the size of that sensor. Today, I'm not going to delve into the details (there are discussions and examples on my web site), but one property that was a factor in photos I made today (and the reason I used the equipment I did) is that a long focal length lens can blur a background more than a short focal length. A very small camera might be advertised to "zoom to an equivalent focal length of 400mm", but that is actually a fiction. The angle of view (what is included in your picture) may be exactly the same as what would be included had the photo been shot with a 400mm lens on a "big" camera (a full-frame DSLR, e.g.), but the actual focal length will be much shorter, and even with compensation in the form of changing lens apertures, there will be no way to equalize the look of the backgrounds in many distance/perspective situations.
So, to photograph these berries and turn the grass and weeds right behind them into diffuse areas of color, I used a 100-400mm, at the long end, on a full-frame camera, with the addition of a 1.4X extender to increase the focal length to 560mm. Computer monitors vary greatly in their pixel density, so the displayed size of an image is not fixed, but if you're seeing this first image as about 4x5 inches, then you're seeing the berries a bit more than twice life size.
Even at f/11, the depth of field is so shallow that only one berry in this cluster is in focus.
Here's an iPhone snap showing the camera setup for that second photo. From this vantage you can't even really see the berries, but they are there, right where the lens is pointed. The black rings attached to the front of the camera body are extension tubes, to allow the whole rig to focus closer. Next is the 1.4X multiplier, or tele-converter (or "extender" in Canon speak), which looks like part of the lens unless you know what to look for. Yes, the tripod is purposely skewed, with the downhill leg longer than the others, and the center column tilted to get the head a little closer to the ground.
Here is the image just recorded, with the camera still in position. Notice how the plants in the background, although out of focus because I focused the iPhone on the Canon's back, are still distinct, especially compared to the berry photo.
Permalink: http://jilcp.blogspot.com/2014/12/camera-size-matters.html
So, size matters, huh? *smiles*
ReplyDeleteI loved seeing the "behind-the-scenes" pictures of you taking pictures! All that technical stuff went in one eye and out the other, though. I'm content to take the basic photos that I take and to admire that magnificent work that you do! And these photos were very meta. Metaphotography, another line on your list of many talents!
ReplyDeleteMost important ... who is getting to eat the berries?!
ReplyDeleteAnon - Yes, I was aware of the implication of my title...maybe it will bring in one or two more readers, right? ;<)
ReplyDeleteJacquelyn - Thank you! I like Metamagical Themas (another book by Douglas Hofstadter).
Anon - I think birds will get the small, unidentified berries, which is good. I don't mind paying for organic blueberries from the market, though if there were tasty ones growing wild here I would be picking them!