i'm a snapshot photographer and know just enough to know i don't know. i know that when you switch film size, all your dof instincts are out the window. i'm using 4x5.
Remember that your lens FP distance (the mm size) is what governs your ability to use a LF camera.
Ergo: A 90mm lens will only allow 90,mm from the FP of the lens tot he ground glass of the back. This will severely limit your ability to tilt, shift, and control dof and brightness because of the limited movement distance and moreover the image circle.
i wanna mimic sally mann's bathroom mirror self portrait and don't have a loop (today; i live in the city without a car and i don't wanna go downtown for one thing). is that a no go?
Not necessarily. But you need to understand that the image she is using what looks like an 8x10. Prob. and older Schneider lens and a few other aspects that you would need to do an exact copy. As a result I would say mimic what she is doing but make the image your own. Use a diff. setup.
it looks like she has less light than me and she did it on 8x10 or something old and huge. so i'm trying to move further away so i get enough dof to shoot at an aperture i can hold still long enough at. cause i think i need to do this at at least f22?
Actually I am willing to bet she prob. shot an f11 on that picture.
but then i realized my camera zooms in and out when i move the back? am i altering the focal length of the lens. well obviously not, but what am i doing?
Actually yes you are moving the focal distance of the lens (see above) and you can only set the focus for that range. The same exact principle is exercised on 35mm cameras. Except the distance is fixed on box cameras, whereas the LF has a moving bellows.
That lens looks like a 135-200mm given the distance seen in the image.
if i move further away and then zoom in i must be reducing the dof i gained by moving further away, right? like switching lenses even though the lens stays the same? wtf is happening?
Not exactly. You have the right idea, but again go back to lens size. if a 90mm lens, then from the focal point of the lens (usually about double the thickness of the lens behind it.
Ergo: the 90mm lens the front of the lens is actually 180mm from the front element to the film plane.
(This is NOT a hard and fast rule. ) Just a general guide. But if you have a 250mm lens, the distance from the front of the lens to the film plane should equal around 500 mm total. This will give you a great deal of movement and decent DoF to work with.
But remember that the aperture size is going to control the actual DoF.
NOT the focal distance.
it looks like i can push hp5 to 3200 with ilfosol 3 and still get a clean-ish image at laptop screen sizes?
The LF size wont only cover a laptop sized image, but will be solid to about 80x100 inches. Image resolution will only degrade on a LF when you reach a huge level of enlargement. But that is if your shooting an actual 4x5. If your shooting a small format camera or such, the image is only as good as the poss. resolution capable based on the format size itself.