4x5 lens won't focus
I set up my camera (Sinar P2 with a Fujinon SWD f/5.6 65mm) in the garage and tried to focus on the TV in the living room about 10m (30ft) away. I move both standards as close together as they'd go, then moved them out gradually, and it would not bring the TV into focus at all (confirmed by looking through an 8x loupe). However, with both standards as close as they'd go, I could focus fine on stuff next to me, just a metre or two (3-6 feet) away.
So, I'm ready for a reality hit: am I just an idiot and doing something wrong? Surely it should focus somewhere between having the standards very close together or as far away as I can get them. Could it be something with the lens? I know it's a wide angle, but even with a small TV image on the ground glass, it should be clear enough to see what's on the TV and not just a coloured square of light. I did mount the lens and shutter myself after buying from KEH... could I have screwed something up?
Thanks a million :-)
It sounds like there is just too much distance between the standards for that lens. A 65 is a really short lens for most 4x5's, and you may need a recessed board to focus at reasonable distances. Does the camera have a standard bellows or a bag bellows on it? If it's a standard bellows it probably cannot collapse enough for infinity focus for that lens.
Keep in mind that to go from your current focus distance of 1 M, to something farther away, the lens needs to move toward the film plane.
Unless it's a retro-focus design, at infinity, the lens will be sharp when its nodal point (more or less where the iris is) is 65mm from the film plane. How far away is it now, with the standards as close together as possible?
if you just hold the lens infront of a wall,
does it focus ? like barry said, it's going to be a tiny distance ( 65mm ) ...
if you can get an image on the wall, you are all set ( as long as your camera can manage )
if it doesn't focus at all ... you may have messed up when you mounted the cells ...
good luck !
There's the problem. To focus on something further away, you need to move the lens closer to the film.
Originally Posted by LFman
"People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.
Few monorails will focus a 65mm lens without a recessed lens board, I'm assuming you've got the lens on a flat board.
Sponsored Ad. (Subscribers to APUG have the option to remove this ad.)
Had the same problem with a 90mm lens. I was able to move both standards on the same side of the tripod block and it just barely worked, but with a 65mm you will more than likely need a recessed lens board.
If you compress the bellows completely and measure from the GG to about the middle of the lens you will find that the distance is greater than the focal length of the lens. Solution, recessed lensboard or longer lens. The focal length of the lens is measured at infinity, anything closer than that is focusable because you extend the bellows.
Originally Posted by LFman
Except that you can move the Sinar P standards together so they touch, giving you around 35 or 40mm between the lensboard and film plane, if I remember right. The OP needs to use a bag bellows with a 65mm lens, a recessed lensboard really makes movements, and especially transfering the movements from front to back on a P, a reall PITA. In my experience, when using a recessed board on a P, there is a lot of reframing and iterative movement calculations due to the offset position of the lens.
Originally Posted by Rick A
The smallest focallenght my Sinar Norma will focus (on a recessed lensboard) is the 75mm and that just barely.
Send from my Electronic Data Management Device using TWOFingerTexting
Technology distinquishable from magic is insufficiently developed
If you are using the standard bellows, there's no way you can focus a 65mm lens at infinity on a Sinar P, and I suspect not even with a recessed lensboard. You need a bag bellows or the ultrawide double bag bellows, and it wouldn't hurt to have a recessed board, and you should probably have both standards in front of the tripod mount. I don't have a recessed lensboard for my 65mm, and I think I've done it with the ultrawide bellows, but it's not a combination I use often.