Kevin M Bourque
3-Mar-2001, 23:17
I have recently started using an 8x10, and have only one lens for it (a 12" Comm ercial Ektar). It's great for general use, and since my camera has 31" of bello ws draw, I can use it at 1:1 and a little beyond.
The tulips have been popping up here in Charleston these past weeks, and I wante d to do some close-ups. I nicked one out of the yard and got ready to shoot. P roblem: you need to go well past 1:1 to fill an 8x10 negative with a 4" tulip. Not enough bellows. So what to do?
Turns out that I already had the lens I needed, in the form of my trusty 150mm C altar, a lens that covers 4x5 at infinity. If you're smarter than me (and I pra y that you are), you already see where I'm going.
The coverage of any lens INCREASES as you move it farther from the film plane. The circle of light coming out of the lens is really a cone. Move the film fart her from the lens and you slice through a fatter part of the cone.
Turns out that the 150mm easily covers 8x10 at the magnification I was using. E xactly how much extension you need to make any given lens cover a given format w ill have to be determined by experiment. We could do it with trigonometry, but how much fun would that be?
Most lenses are optimized for use when the distance to the film is less than the distance to the subject. Anyone tried turning their lens around backward when going past 1:1? I guess you have to drill a hole in your lensboard so you can t rip the shutter.
All of this is blindingly obvious to some of you, so just chuckle and move on. Everyone else, give it a try sometime!
I'm a little smarter today that I was yesterday, so now I get to take Sunday off . Next week's point to ponder: why do I keep my eyes tightly closed when I'm lo ading film holders in the darkroom? Hmmm.
The tulips have been popping up here in Charleston these past weeks, and I wante d to do some close-ups. I nicked one out of the yard and got ready to shoot. P roblem: you need to go well past 1:1 to fill an 8x10 negative with a 4" tulip. Not enough bellows. So what to do?
Turns out that I already had the lens I needed, in the form of my trusty 150mm C altar, a lens that covers 4x5 at infinity. If you're smarter than me (and I pra y that you are), you already see where I'm going.
The coverage of any lens INCREASES as you move it farther from the film plane. The circle of light coming out of the lens is really a cone. Move the film fart her from the lens and you slice through a fatter part of the cone.
Turns out that the 150mm easily covers 8x10 at the magnification I was using. E xactly how much extension you need to make any given lens cover a given format w ill have to be determined by experiment. We could do it with trigonometry, but how much fun would that be?
Most lenses are optimized for use when the distance to the film is less than the distance to the subject. Anyone tried turning their lens around backward when going past 1:1? I guess you have to drill a hole in your lensboard so you can t rip the shutter.
All of this is blindingly obvious to some of you, so just chuckle and move on. Everyone else, give it a try sometime!
I'm a little smarter today that I was yesterday, so now I get to take Sunday off . Next week's point to ponder: why do I keep my eyes tightly closed when I'm lo ading film holders in the darkroom? Hmmm.