out of focus image to one side

[andy_4218]

any ideas on this problem. Using a sinarx with a zoom2 roll film holder 6x12 outdoors using 47/72 lenses ..it quite often tends to go out of focus just on the extreme right of the resultant image. No horizontal shifting has taken place and centre filters are being used. If it was wind or vibration then surely it would be random or affect the whole image. Im taking pictures of landscapes and everything is pretty much at infinity...the wind doesnt seem to be very strong at all..barely a slight breeze. This problem seems to occur with long exposures at f22 over say 20 secs on the evening shots. I use cable release. I have a feeling that the problem must be vibration based but if anyone has had as similar experience i would be interested to hear it. Thanks...andy

[Bill_1856]

Most probably a lack of film flatness. Do you have the problem using cut film in a regular holder?

[andy_4218]

well i did consider this but then i would have the problem all the time ..even during short exposures.

[Ken Lee]

Could it be that when you insert the back, after focusing, that the camera moves slightly, or that the rear standard comes out of alignment ? You might find it helpful to shoot an image of a brick wall, from straight on, and check the focus with a loupe "before and after" inserting and removing the holder or back.

[andy_4218]

once again i would see this problem occur at short exposures but all my daytime stuff is tack sharp?

[Diane Maher]

I'm not familiar with that roll film holder, so I'll ask a few questions. Does it affect every image on the roll? Perhaps when you are advancing the film, that action is enough to loosen something? As you have said, your short exposures are fine. Are you shooting roll film during the day (I'm assuming you are)? Are your standards level?

[Sam Crater]

Is it colder when you are making your evening long exposures?

[Leonard Evens]

It could be a problem with film flatness. But first you should check that your standards are really parallel. For wide angle images, a very slight swing would produce just what you observe. Sometimes the detent positions or zero positions are slightly off because of play or other reasons.

The easiest way to check if the standards are parallel is to rotate the tripod head 90 degrees so the rail or bed is plumb. Adjust using a bubble level on the gg so that it is level. Then, check if the front standard is also level. You should use a surface which you've previously checked is consistent with the front housing of the lens.

You can also focus on a flat surface and make sure the lens axis is perpendicular to it by making careful measurements from the lens to the subject points correpsonding to the corners of the image. Using a high power loupe should show you if the exact subject plane is not consistent with the nominal focus surface. However, if your lens has some field curvature, it may happen that the focus is different at the center than at the corners. It should be essentially the same in all four corners, though.

[Andy Eads]

It is possible that the film has taken a set while wrapped around the rollers. If the film was left partially exposed for a length of time, the the area with the set would not lie flat. Since it happens only at one end of the frame, I would suspect this is the problem. I envy you for that holder!

[andy_4218]

...thanks for the response guys and i appreciate it. Most of the questions would be valid if the problem occured at short exposures as well as long. I was wondering how much a slight deviation in the setting of the standards would matter at wide angle if you are shooting at infinity and stopped down to f22? The roll film holder seems flat enough...ive put dead rolls through it to inspect by eye with the darkslide removed. The temperature is a pretty constant 18-25 even at night (hong kong). I have noticed this problem with different lenses and 4x5 holder too....i think my technique may be to blame. I plan to concentrate on using umbrellas more ..tightening everything more..firing the shutter and then pulling away the darkslide from the lens to start the exposure...but why this problem should occur just to one side confuses me.