ND filter on long lenses for lowering shutter speed

[Paul Schilliger]

I am looking for a way to avoid using the difficult low speeds 1/8-1/4-1/2 with long lenses (these speeds produce unsharp images). I thought of using a +3 ? ND grey filter. However, I am not sure a filter won't alter image quality when used on a 300-450 or 600mm lens. I have once had a 360 shot blurred on one side beca use I inserted a color correction filter aslant in the Cokin holder, so I am not using them any more. I think using the Cokin +3? ND that I have may not be the best idea, for the risk of reflexions on the filter too, but what about a good t reated screw in filter? Should it preserve the long lens quality?

[Doremus Scudder]

Paul,

You should have no problem using good-quality optical glass ND filters on any lens. Scew-on filters are best to insure parallelism. I am, however, a little confused as to what you are trying to accomplish. In my experience, 1/8-1/4-1/2 second exposures are just as sharp as any other speed as long as subject/camera movement and film shift aren't degrading the image. Just what unsharpness are you experiencing that is shutter-speed related? I'm curious. Maybe there's something I missed here. Regards, ;^D)

[Paul Schilliger]

Thanks so far. Doremus I might have started another controversial discussion her e, but I found that these low speeds produce vibrations that are affecting image sharpness. Albeit not a probl em on short lenses or large stable cameras, this is a concern on extended 4x5 cameras where the lack of stif fness of the lensboard mount is prone to be affected. Making exposures 1/30 and shorter or one second and lon ger helps solve the problem.

[Bill Glickman]

Paul, consider trying a Bogen 3252 / LONG LENS CAMERA SUPPORT This will provide you with two points to stable the long rails. If you are using newer lenses, I don't think the unsharpness is caused by the shutter, but rather the tiny vibrations in the camera or tripod. Have you tested this to see if longer exposures would solve the problem? I shoot at these ss all the time and have not experienced this. However, I have experienced unsharpness when not shooting at the f stopd designed for that specific lenses. I always uses dual support when I go past 360 on 4x5. Some of my 1200 Nikor shots are super sharp on the VX.... But if you run this test and find your hunch to be correct, I would be very intersted in knowing this. I often suspected this, but never experienced it...

[Doremus Scudder]

Paul,

Greetings from Vienna! I understand the possibility of vibrations adversely affecting the image, but assumed this was a problem with focal-plane shutters and reflex cameras with mirrors that flop around during exposure. I would be interested in hearing in more detail exactly what problems you seem to be having and if you have done any tests to determine exactly which speeds are suspect, as well as shutter size, bellows extension, type of camera and tripod mount, etc. etc. I draw the bellows on my little field camera pretty long sometimes and am now going to test and see if such shutter speeds do cause image-degrading vibration. This may be yet another hidden source of image degradation to deal with. Thanks in advance, ;^D)

[Paul Schilliger]

Well, yes I have used a third arm, like the Bogen but self made and a bit lighter (the Bogen clamps are a bit heavy outside the studio). It is not giving me good results in light breeze, because all the tripod moves, but should be enough to damper the shutter shake. But now that I have a second clamp and extension on the VX, I would use a second tripod and that's excellent, even it's harder to setup.

I have made a simple test that a contributor to this forum suggested to me a whi le ago that you can do also to check for shutter shake. Take a bit of electrical cord, cut 10-15 inches and strip the wire, then pull out one thread and fix it on the lens or camera with some tape or by twisting it around something or pinching it with the lens cap (careful with the glass!). Make it come forward by about 8 inches. Then operate your shutter and watch for any movement in the end of the w ire. I'd be surprised if it stays steady at all speeds, unless the camera is very stiff. You can easily guess what the vibration, even small, can do to a long lens shot. The vibration lasts only for a fraction of a second, so when you have long exposure times, it does not affect image sharpness so much. I have seen from a longtime that shots lasting a second and more are sharper than shots taken at slow speeds. This was obvious when I used a Technika overly extended with Wista Macro tube and only one tripod. Probably not a problem on heavier, more rigid cameras.

[fw]

I'm going to try that test with my Fuji 400T ; getting a loupe noticeably improved the results with this lense, and maybe there is something more to do with the camera stability. However I really do not want to add any more items to my backpack - there's enough heavy stuff in there already.

[Paul Schilliger]

Dan, I thought of a -3 stops (or 8 x) grey filter, to make it worth it. Should m ake focussing pretty dark on a f12 lens ;-)

David, I know what you mean. These packs are crazy!