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Sarah
4-Sep-2004, 16:52
I'm trying to focus my 4x5 Cambo (with 150mm lens) on infinity, but can't for the life of me. I found another posting that was similar to this one - but the solution there was to reverse the front standard. ?? I tried that but it did not help. Any other ideas?

Thanks, Sarah

Doug Dolde
4-Sep-2004, 16:54
Weird. That should be pretty easy. Are you using a lupe and darkcloth? Maybe it's in focus and you can't tell. Also be sure to focus with the lens wide open.

Sarah
4-Sep-2004, 17:00
Yup - using all the normal equip. It's not even close to being in focus. I can only focus on objects that are within about 5ft of me.

This is a new camera for me (just got it off ebay) - all the ones I used before I could pretty much focus on infinity (approx) without even looking at the groundglass as long as I knew the focal length of my lens. But with this one, with the bellows at 150mm, nothing is in focus.

phil sweeney
4-Sep-2004, 17:03
I bought a lens from KEH a few years ago and eventually returned it. As you describe it just would not focus.

Jorge Gasteazoro
4-Sep-2004, 18:09
Have you check that the cells are screwed all the way in? It is the only thing I can think of that would do this.

Paul Butzi
4-Sep-2004, 18:10
It's a strange situation. For virtually any 150mm lens intended for 4x5, the flange focal distance with the lens focused at infinity should be very close to 150mm.

It's tough to imagine a 4x5 camera where there's some constraint that will let you get the standards far enough apart to focus at 5 feet with a 150mm lens (it should be about 166mm) but not get them another 16mm closer together to focus at infinity.

Are both the lens and the camera new to you, or is it just the camera that's new to you and the lens is a lens you've been using before?

Because if you can get the standards into position so that the flange to filmplane distance is 150mm, and you can't get the lens in focus, then I would suspect there's some problem with the lens.

How far apart are the standards when you have the lens focused on something at 5 feet? You can use the lens rule, the distance between the film plane and the flange of the lens, and the distance from the lens to the object in focus to calculate the focal length.

The lens rule is 1/f = 1/v + 1/u, where f is the focal distance, and u and v are the distance from the film to the flange, and from the flange to the object in focus.

Michael Kadillak
4-Sep-2004, 20:34
Here is a wild suggestion in the "I don't have a clue as to what to do from here category?"

Take the front standard off of the camera. Take the bellows off of the back standard and set them aside leaving the ground glass and the rear standard all by itself. Hold your lens on the lensboard in your hand and put your darkcloth on the edge of the lensboard and over the ground glass and try to manually move the lens forward and backward to see if you can get anything to happen that appears to be a focus at about the 6 inch mark.

If the elements are screwed into the shutter correctly and the lens focuses at less than infinity, something is just not right. All I am attempting to do with this suggestion is eliminate a few variables and see what happens.

If for some reason this does not bring about an improvement of the situation, something is awry and the lens needs to go back for another or a refund.

Good Luck!

Robert Brown
4-Sep-2004, 21:25
Hi Sarah--

Two possibilities come to mind-I have had both happen:

1)You have a lens with mis-matched lens cells. Is your 150 of modern design and of a major make (Scchneider, Nikon, etc) Check to see if there are serial #'s on both front and rear cells (although many do not have numbers on the rear cell). A front cell of a 150 with a whack-o rear cell of some sort wont focus for beans.

2)You have a lens with an interior element that has come loose and has stuck in the wrong position. Remove the cells from the shutter and GENTLY rap them in your hand to see if something inside moves. It would most likely be in the front cell.

Hope this helps--

Bob

CP Goerz
4-Sep-2004, 22:18
Take off the lenscap.

CP Goerz.

Leonard Evens
5-Sep-2004, 09:03
You can make a quick estimate of the actual focal length by holding the lens up---not mounted on the camera----in front of a wall and focusing a distant image on the wall by moving the lens back and forth. Then measure the distance from the lens to the wall. That should be the focal length.

If you can focus at 5 feet (1524 mm), you should be able to focus at infinity by moving the lens closer to the ground glass. Perhaps the problem is that for some reason the effective focal length is very short and you can't bring the standards that close together. That is the only explanation which comes close to making sense. If the closest you can bring the standards is about 75 mm and the effective focal length comparable, that would explain what you are seeing.

Sarah
5-Sep-2004, 19:09
Thanks for all of your suggestions! (Except for that lenscap one :P)

I'm trying them out now...hoping to have a solution soon.

Cheers, Sarah