Focusing a TLR
I took some pictures last roll of film of some manikins, two of them, very close to the camera (Rollie 3.5T) I moved as close as the camera would focus (about a meter), then back a bit so that I could move the focus back away from the closest point. I used f/5.6 to minimize DOF, but not wide open. I took 3 shots - first focused on the closest manikin, second focused on the far manikin (two feet further away), then stopped way down for the third shot, and used the distance scale to set the focus to include both manikins with the greater DOF. I was very careful in focusing to be sure the pop up viewing magnifier was well positioned.
Both negs from the first 2 shots indicated focus was further out than I thought I saw on the ground glass (the first shot was actually closer to the farther manikin, and the second looked just beyond the farther manikin) the stopped down one is ok, too hard to tell where the center point is.
I just had my 3.T serviced (Krimar), and one of the things he did was calibrate the focusing. Is it possible that the focusing lens could be in focus, and the taking lens out of focus to that extent? I'm not concerned that the distance scale is accurate, just agreement between the lenses. I have never had this problem, although I don't normally focus this close.
I'm going to run another more controlled test with wide aperture, with gradually distant subjects marked, etc, like those old DOF examples you used to see in books, and record everything, and might call Krimar if it repeats itself, but I just wanted to toss this out to see if anyone has any advice.
If you were hand-held did you maybe tilt or lift a little to compensate for parallax and lose critical focus?
As you already know a controlled test will determine whether a problem exists or not. If you have a screen you can use on the film rails you don't need to use film.
You should definetely use a tripod for further testing. Moving a camera with waist level finder out of focus happens easily.
Best regards, Benjamin
You may want to test using a test target or a newspaper. Keep it straight on, no angles, camera on tripod, and test using ground glass focus with a magnifier, then follow with a ruler/distance scale shot. All wide open, starting at 3 foot or what ever the close focus is, then 4 foot, then 5 foot, then compare.
Maybe the repair guy did not get it right.
I suggest opening the back and placing some frosted celo tape across the film rails. Then view something like a light bulb. You can use a magnifier if you want. The tape acts as a ground glass at the film plane to confirm focus of the viewfinder.It is a little awkward with a TLR, but you can figure out a way of keeping the same distance from camera to subject when first focusing by viewfinder, and then by frosted tape.
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Thanks, guys, for the responses. I failed to mention that it was on a heavy duty Bogen that I normally use for the 4x5, with cable release. I didn't think to mention it, because I hardly ever shoot hand held any more, except occasional 35mm.
Better yet, is to cut a piece of flat clear plastic, like the lid on a CD case, to fit the film chamber. Then put matte Scotch Magic tape strips on one side, and you will have a cheap, fine grained and usable viewing screen.
Originally Posted by Jon Shiu
Both negs from the first 2 shots indicated focus was further out than I thought I saw on the ground glass
The major problem with 120 film: it won't hold flat all the time. The film cannot bulge back behind the pressure plate, it can only come forward. Therefore, the focus shift is always behind the subject.
Unless you have a vacuum back, the effects can be random. For critical work I bracket the focus. Also, pay attention to the time between shots. If the film sits for 2 years straddling a roller, when it is pulled into the gate it likely will bulge.
I have heard of 'advice' from seasoned professionals that seems to correct the problem, without exactly knowing the problem. One set of advice involves doing landscape work at the hyperfocal distance. In this case when the film bulges, it puts the image right at infinity (where you want to be).
The second is to focus a portrait just in front of the subject. Again, when the film bulges, it will bring the subject into focus.
Did you use a center-spot focusing aid, then
move the camera to compose for the shot?
This is a common mistake newcomers to
Rolleiflexes make -- if you are shooting close
to your subject, with a wide aperture, you
will end up with the focus off in the way you
have observed. The fix is to ignore the
center spot and teach yourself to focus on
the glass, without moving the camera to
recompose after you focus.
It is not "film bulge" -- not a Rolleiflex issue.
Last edited by Rolleiflexible; 03-27-2010 at 09:33 PM. Click to view previous post history.
You don't need a tripod just to focus with a Rollei TLR. That's ridiculous. There is a focus distance scale in plain site, on your focusing knob. It'll tell you everything that's going on, with how you've set your critical focus. Just read it, and trust it.
Tripods are insane with a simple TLR. They're fast/hand-held beauties. I've been shooting with Rollei TLRs for decades, and believe me, they're just about as perfect as it gets.
If the lens doesn't read "ZEISS", then it just isn't.