Will Extreme Stretching of Bellows Effect Sharpness?

[bakerbang]

Hello,

I am using a Sinar P for Macro work. The Bellows extension is just over 1000 mm using two bellows and 3 Standards.

One of the bellows is slightly older than the other and is incredibly stretched to reach the required distance. Focusing is extremely difficult even with several extra redheads on the subject just for focusing.

My question is because of the bellows being over stretched is it possible it's making focusing difficult and effecting overall sharpness on the final image? I appreciate there are a number of possibilities that could make an image soft but let's imagine I have spent weeks eliminating them!

Thank you
www.jon-baker.co.uk

[David A. Goldfarb]

At max extension I'd just be concerned that the front standard might be flexed out of parallel, even on a Sinar P, but you can look at the bubble levels to confirm that.

[Ken Lee]

I shoot macro with a Sinar P. Keep in mind that the focusing mechanisms don't have locks. They are very sturdy but I have noticed that if I point the camera straight down with a heavy lens on the front standard, some focus shift is possible. It happens slowly, while you are loading the film and making the shot.

One recommendation would be to use a shorter lens. At macro distances, even a modest decrease in focal length translates to a large savings of bellows draw.

For example at 1:1 a 250mm lens requires 500mm bellows draw. A 200mm lens requires only 400mm of draw, a savings of 100mm or 4 inches: enough to make the difference between comfort and... agony

Another suggestion is to shoot in horizontal orientation.

[Bob Salomon]

,

I shoot macro with a Sinar P. Keep in mind that the focusing mechanisms don't have locks. They are very sturdy but I have noticed that if I point the camera straight down with a heavy lens on the front standard, some focus shift is possible. It happens slowly, while you are loading the film and making the shot.

One recommendation would be to use a shorter lens. At macro distances, even a modest decrease in focal length translates to a large savings of bellows draw.

For example at 1:1 a 250mm lens requires 500mm bellows draw. A 200mm lens requires only 400mm of draw, a savings of 100mm or 4 inches: enough to make the difference between comfort and... agony

Another suggestion is to shoot in horizontal orientation.

Or add an aux. standard and another bellows, and maybe rail.

[Ken Lee]

If you need to shoot downwards onto a table, you can use a mirror at a 45 degree angle: this will keep the camera level.

Another option - from the old days - is to use a reversing prism. See this old Goerz catalog on cameraeccentric.org, page 26.

[DKirk]

What is it you're photographing? As a while back we were using a Sinar (part Norma, Part F) set up for photomicrography (Top floor of the Glasgow College of Building and Printing) - one factor that affected sharpness was the trains on the Queen Street low-level line. . .

[Jim Noel]

If a bellows is extended to the point of smoothing out the pleats it defeats one of the purposes of a bellows - elimination of most internal reflections. This may make focusing difficult, and it will result in no-image forming light, or fog, and less contrast in the negative.

[Doremus Scudder]

... and, if your bellows is stretched too tight it can pull the standards out of alignment and even pull the focus back shorter (reverse focus creep) in the time it takes to insert the filmholder, pull the slide and make the exposure. I second the idea of using a shorter lens. You'll likely get better results that way anyway.

Doremus

[bakerbang]

Wow thank you everyone for your advice it's been very helpful. I have taken apart the camera and had a good look at everything, there is slight movement in the bellows if the camera is pointed down, something I haven't noticed before. I think investment in another standard and another bellows will be helpful as when they are maxed out focusing is almost impossible.

Another lens is also a possibility, at the moment I am using a schneider 150mm any advice as to what would be a good replacement lens in this situation
maybe a dedicated Macro?

Thank you
Jon

[bakerbang]

What is it you're photographing? As a while back we were using a Sinar (part Norma, Part F) set up for photomicrography (Top floor of the Glasgow College of Building and Printing) - one factor that affected sharpness was the trains on the Queen Street low-level line. . .

Hi DKirk I am photographing succulents and other plants then cross processing the film. I am making the images on a poured concrete floor in a basement with a very large tripod.

I would be very interested to see the images from your photomicrography experiments,

best

Jon