cut corners on negative

[12pmc]

Hello. I use a Technika IV and Toyo film holders. On viewing the negative the corners , all four are cut off slightly, just a few millimetres. When I load the firm, seems easy and goes ok, as when I unload, the sheet comes out fine.

Any suggestions please

Thanks
Peter

[Teodor Oprean]

I think you have noticed the phenomenon of mechanical vignetting in the far corners of the negative due to the design of the rotating back.

[Bob Salomon]

And you may be seeing this with 210mm lenses and longer.

[12pmc]

That answers that - looking at my record book it occurs with a 240mm lines not a 150mm. Is this something one lives with or is there any way to avoid it?

Thank you for both for your comments, as you may guess I have only recently started using an LF camera.

Peter

[J.Koger]

Did you use a lens hood? This may cause vignetting at small aperture. What is the 240 mm make lens? google the lens name +image circle and that may give you a link to see the tech specs of the lens, if not too obscure. Are you using a 4x5 format? Read this for some background: http://www.bhphotovideo.com/FrameWork/Product_Resources/SourceBookProPhoto/Section04LgFormatLenses.pdf. The minimum image circle for 4x5 is 154mm. You need a lens which gives a larger image circle than your film size requires. Movements require even larger circle. I always use the specs of the Nikon SW series lenses as a guide for specs to look for.

[AJ Edmondson]

Essentially you learn to live with it as it isn't (in this case) a result of lens coverage! As Teodor noted, it is the result of the design of the rotating back. The Wista metal field cameras with rotating back exhibit the same problem... perhaps the one "mitigating" factor is that with many of the 4x5 metal-frame negative carriers this occurs outside the useable area of the film.

Joel

[12pmc]

Joel and J. Lodger - thanks for your comments, I did not think is was vignetting, but will look at the BHP pdf for interest.
Thanks
Peter

[Bob Salomon]

That answers that - looking at my record book it occurs with a 240mm lines not a 150mm. Is this something one lives with or is there any way to avoid it?

Thank you for both for your comments, as you may guess I have only recently started using an LF camera.

Peter

Yes, it can be eliminated by having a machinist cut off the parts of the casting that are in the corners but then you can't rotate the frame. If you take your negative with the cut corners and place a straight edge acroos the long and short sides (pieces of paper placed under the negative on a light box) will let you see exactly how much of the corner is cut off. Since this effect has been on all Technikas since before the start of WW II it really isn't much of a problem.

[12pmc]

Bob - thanks, compose accordingly is the answer.

[Teodor Oprean]

I checked just now. The Meridian 45B has the exact same design flaw.

[karl french]

Use 9x12cm film.

[Cor]

..or use a Durst L1200 laborator to print your negatives, the standard negative holder is actually designed for 9*12, and you will not be able to print these cut off corners..I have a Tech IV (well it's a Color) and a L1200..:)

Best,

Cor