After scouring the internet, I've read mostly for macro work the focal length is of little consequence anyway.
After scouring the internet, I've read mostly for macro work the focal length is of little consequence anyway.
The one third front DOF, tiw thirds back DOF works only at one distance the hyperfocal distance divided by three. It may work approximately for moderately short distances, but it works neither for close-ups nor for distant subjects. In the former case, close-ups, the near DOF and the far DOF are approximately the same. If you focus at the hyperfocal distance, the far DOF is infinite, which is much larger than twice the near DOF.Originally Posted by Lachlan 717
Before you spend any more money on gear. . .
My understanding is that dof is based on focal length, f-stop, and focus distance. And that for the same film format, the dof is the same if the object magnification is the same, I.e. If you compose the exact same scene with a 150 or a 300, at the same f-stop, the dof will be the same. This of course does not apply across format, so the same scene with a 50mm on a 35mm camera will have greater dof than the equivalent scene on a 150mm on a 4x5. So, if you are shooting the same area with your 150 as you are with a 300, you will get the same dof at the same f-stop, since you have to get closer with the 150 to get the same magnification. Optics experts, feel free to correct me on this. All this to say, why don't you try your 150 closer to your object, since you most likely will have the bellows capacity, and see if you like the results before being new lens and rails.
From the softness standpoint I agree with the film flatness comment above, but also am concerned about the scanning. If you are only scanning at 300 dpi on 4x5, you're printing 24x30 at 50 ppi, which would make a soft print. I don't know the flextight scanners enough to comment other than they are capable of much more than 300 dpi scanning.
Good luck, and the first teaserr shot looks like this will be an interesting project.
Cheers!
Bill
Lots of good advice here, but consider this:
From what I can see, you are close to the "macro range" here. That means that focal length won't affect DoF, since the reproduction scale is what you frame for - and at the same reproduction scale, DoF is independent of focal length.
Most LF lenses are optimised for :10 or 1:20; macro lenses are optimised for 1:1. It looks to me as if you're somewhere between those, and as far as I know there is only one lens (or set of lenses) optimised for 1:3 : The old convertible Schneider Symmar.
They are surprisingly good, and with the exception of the 150mm the cells can easily be swapped for very close macro, at 3:1.
Also, don't worry about diffraction: In your setup the DoF is the limiting factor even at f:32.
This is a classic case of misstatements concerning DOF. I would have expected better from our team of LF experts.
DOF is not determined by the focal length at all, but by the magnification and Fstop period.
So at 1:1, and f45, any lens you use will give you the same distance of focus in front of and behind the subject. The only exception to this rule is when wide angles reach infinity sooner then longer lenses, but this is for landscape work.
That said, to maximize DOF for landscape work you need to incorporate hyperfocal focusing.
I suggest the Nikkor 210mm AM lens which is optimized for what you are trying to accomplish. It is overkill as to coverage but the images at 1:1 are stunning.
I've used lenses from my enlarger for that with a temporary cardboard lensboard. Those lenses are designed for magnification. Think of the ground as film in an enlarger. If you're outdoors, the problem will be to find something to use as a shutter. In a studio you'd just use the lights themselves. Good luck.
I've been practicing while my lens is in the mail and I've run into some issues about exposure.
I'm aware that the effective f stop = (f-stop) (1+ magnification) So I have to compensate my exposure, but my question is, do I still have to compensate for bellows extension as well? Or does that fix the exposure already? Thanks for your patience guys! I appreciate it.
So if I've at 1:1 and I'm stopped down to f22, my effective f-stop would be 44? My bellows would extension would be about 18 inches at 1:1 because I'm using a 210mm lens.
Carlos
Last edited by carlosmh1910; 13-Mar-2012 at 09:06. Reason: Forgot calculations
If I saw some screen shots of your settings in FlexColor for your X1 scans, I may be able to decipher the problem with resolution capping out at 300dpi. You should definitely be getting more out of that scanner (it has a max optical resolution of 2040dpi for 4x5" films). Screen shots of the Setup window (File>Setup>General Tab) and of the main window of FlexColor (with all the options on the left) might help.
Effective f stop as you calculated is based on extension so it is the same as bellows extension. Using both would be double counting.
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