No I don't have a 16X20, but mine could be expanded to that with a DIY extension back.
Like this, a wedge shaped box. https://www.largeformatphotography.i...l=1#post953322
What is the question you want answered?
Originally Posted by maxi0909
Unbelievable to throw such a beauty away
Do you have a 16x20 one?
Maybe you can answer my last question from above?
Tin Can
You don’t need a camera to determine the coverage. All you need is a widow, a dark room and a white surface. Hold the lens pointing out the widow at a distant object and see how large a circle it throws onto the white surface. If possible, draw a 20” circle on the surface to make visualizing coverage better.Unbelievable to throw such a beauty away
Do you have a 16x20 one?
Maybe you can answer my last question from above?
I wanna know why i should get a lens with an aperture of for example 4.5 instead of my lens, which has f10
Because i think it will be impossible to photograph someones face with 4.5 at a 16x20 camera
Or is it just for focussing, so the focussing plate is bright enough - and the i will bring down the aperture?
Am I right?
But there are some dudes out there which photograph which projection lenses who have a fixed f stop like 4.5
http://www.dofmaster.com/dofjs.html
Calculate using 8x10 film (0.2 CoC), 24" lens at 1:1 magnification, f/10, the DOF is approximately 9mm.
DOF is complicated but this is a rough estimate. If you want the whole face in focus you are going to have problems, even at f/64 (50mm DOF).
There's no free lunch unfortunately.
You need to study a bit.
f 4.5 is not the deciding factor in image circle.
Click below.
Depth of Field (DoF), Angle of View, and Equivalent Lens Calculator
Tin Can
maxi, aperture affects image circle in two ways.
First, with some lenses the mechanical design is such that with the lens wide open the rear of the barrel blocks the outer part of the cone of rays that the lens projects. Stopping down makes the exit pupil smaller and reduces this problem. What's affected here is the circle illuminated, not the circle of good definition. Once the exit pupil is small enough to eliminate mechanical vignetting stopping down farther doesn't increase the size of the circle illuminated.
Second, some off-axis aberrations are sensitive to aperture. See https://web.archive.org/web/20141229...rg/optics.html for a list. They are better controlled when the lens is stopped down; this improves definition. But and however, stopping down increases diffraction's effects, reducing definition. The effects of residual aberrations and diffraction have a minimum and the circle of good definition has a maximum at some aperture. Which aperture depends on the lens. At all other apertures the circle of good definition is smaller.
Please understand that resolution needed on film depends on how much the negative is to be enlarged. Negs to be contact printed don't have to be as sharp as negs to be enlarged, and the more a neg is to be enlarged the sharper it has to be.
Point taken Dan.
Let’s see if OP returns.
Tin Can
But I don´t talk about image circle anymore, I just wanna talk about DOF
I wrote to Kurt Moser, who´s a german too and he told me that he takes portraits with projection lenses that have apertures like f4
unbelievable, but he says it works well
DOF is variable, you need to plug numbers into the calculatores we linked to.
Tell us more about you, the project and why you are doing this.
A good story always helps.
Tin Can
Just test it like everyone is saying. Use a cardboard box, and a translucent bag as a DIY focus screen. Find a friend to sit at the distance you think you will likely shoot from. You can see exactly what the lens will do instead of guessing. It's really simple and in 5 minutes you will have definitive proof of if it works for your application or not.
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