PDA

View Full Version : Educate me on tilting lenses



buzzardkid
20-Oct-2015, 08:55
Question: when I tilt the lens on my Graflex Speed Graphic 4x5, will it influence sharpness, or just shift focus? Or neither of those two?

I gave it a try with a Kodak Aero-Ektar 2.5/178mm (stopped down to f5.6), but results looked less sharp on the negative than they appeared on the ground glass. Not completely ruling out the ground glass being misaligned either, I gotta admit.


But since I gotta start somewhere when it comes to identifying the issue, thought I'd tap into the vast knowledge here and ask what tilting a lens actually does to sharpness or focus.

Thanks for educating me!

Bob Salomon
20-Oct-2015, 09:02
Neither.
When you tilt the lens so that a line drawn between the lens the image and the film will intersect on a common plane (some say point) then you have changed the plane of sharp focus from a point near the lens to almost infinity, even wide open. In other words you tilt the lens and you change the plane of sharp focus.

IanG
20-Oct-2015, 09:05
Lens tilt will shift the plane of focus, used correctly that can increase sharpness.

You need to check the focus with no tilt first. If your back is missing a fresnel then the glass will be out of register, however not all Pacemaker Graphics came with a fresnel that includes the Graflok backs. The actual focus screen frames look almost identical and have the same casting number but the one for a fresnel is machined to allow the fresnel to be fitted without affecting the register.

Ian

Doremus Scudder
20-Oct-2015, 09:32
Question: when I tilt the lens on my Graflex Speed Graphic 4x5, will it influence sharpness, or just shift focus? Or neither of those two?

I gave it a try with a Kodak Aero-Ektar 2.5/178mm (stopped down to f5.6), but results looked less sharp on the negative than they appeared on the ground glass. Not completely ruling out the ground glass being misaligned either, I gotta admit.


But since I gotta start somewhere when it comes to identifying the issue, thought I'd tap into the vast knowledge here and ask what tilting a lens actually does to sharpness or focus.

Thanks for educating me!


An education is what it is too :)

The answers you've got are right, tilting (or swinging) the lens moves the plane of sharp focus around in front of the camera (that's kind of "shifting focus..."). That will allow you to position it to get what you want in that plane. Stopping down will give you a depth-of-field that extends on either side of that plane. These two things together, in experienced hands, allow the photographer to control what is in and out of focus in the final print.

(FWIW, the plane of sharp focus moves around in a mathematically predictable way when applying tilts and swings (swings being tilts 90 transposed). If you're the mathematical type, search for "Scheimpflug" and for web pages on view camera technique by "Merklinger.")

Learning how to manipulate camera movements to your best advantage, and to the fullest, requires a bit of study. Fortunately, the basics (and the most common movements) can be mastered fairly easily.

A Google search on "view camera movements" will yield tons of info. For ground-glass alignment issues, search and/or ask here (Ian Grant is your man here and Graflex.org will help a lot too).

You've begun an exciting journey. I wish you much fun.

Best,

Doremus

buzzardkid
20-Oct-2015, 16:18
Thanks all for your answers! Ian, Doremus, I'll get back to both of you on the possible focus issue and on the inspiring photographs!

IanG
20-Oct-2015, 16:35
I have a few Speed & Crown Graphics, the ones I use most have fresnel screens. I have two Graflok focus screen frames one with a Fresnel the other without and I should actually measure the differences in screen position (both give perfect focus), Dan Fromm has described the differences but I've never seen the actual measurements or an easy way to tell which frame you have. Both the spring back and Graflok came in the two versions.

It's useful to know that if a fresnel has been added to a focus frame designed for just a GG screen the Pacemaker focus hood won't lock in place unless you shim the clips holding the glass in place, and you have to add the fresnel to the back of the GG (not the lens side), I did this and greatly increased brightness.

Ian

Jim Noel
20-Oct-2015, 18:40
Neither.
When you tilt the lens so that a line drawn between the lens the image and the film will intersect on a common plane (some say point) then you have changed the plane of sharp focus from a point near the lens to almost infinity, even wide open. In other words you tilt the lens and you change the plane of sharp focus.

To be accurate - the planes meet along a line. Lines meet at a point.