View Full Version : Caltar 165mm 'limited movements' but how limited?

Tobias Key
15-Sep-2010, 03:49
Hello everyone!

I recently purchased a Toyo monorail kit with a Calumet-Ilex 165mm lens. After doing a bit of research I've found out that the image circle is 206mm, thanks to Michael Gudzinowicz's excellent reference page. What I'd like to know is how much lens tilt would this give me before vignetting occurs or if there is an equation that will let me work this out for myself?

Many thanks in advance


Brian Stein
15-Sep-2010, 04:38
hop across to http://www.largeformatphotography.info/lenses/ and download the 4x5 lenses excel spreadsheet. You can then examine the formulae used to calculate tilt etc, or just find a lens with around 206mm coverage and note that you will get around 25 degrees tilt in landscape orientation, and a bit less in portrait.
I am not sure how this helps apart from deciding its quite a bit, which you might have guessed based on the image circle being quite a bit larger than the diagonal if the negative (4x5 being about 150 mm).

Tobias Key
15-Sep-2010, 05:27
Thank you Brian

I'm just really looking for a rule of thumb really as I'm new to LF and have no clue as to what I can get away with. I haven't been able to find a huge amount on the lens but did find a PDF of a 1970 Calumet catalogue, which described the lens as having 'limited movements' whether this means the outer limits of the image circle are ropey and not usable I don't know. But as 4x5" isn't the cheapest thing in the world I don't want to do any testing that's unnecessary.

Brian Stein
15-Sep-2010, 06:26
Ok two issues here.
1. mechanical vignetting. most modern lenses (say 1950 onwards) were made to mechanically vignette before running out of circle of illumination at a point the manufacturer decided on. Older lenses vignette by just running out of area they will throw light on.
2. acceptable sharpness. To some extent this depends on what *you* call acceptable, which in turn depends on whether you are enlarging and by how much. For example Schneider tend to have a fairly conservative idea of what sharp is so many of us find their lenses cover "more". If you are contact printing 10 lpm at the edge is plenty, but not if you want 5x enlargement and so on.
Older lenses seem to cover more because there is not the manufacturer induced mechanical vingetting, but you will find the extra may be smoosh....

At the end of the day all of us have to make the call about what we think is "ropey and unusable". In general with a modern lens like your caltar you should have good results until you start stretching the bellows. As a vague milestone for landscape often 5 or 10 degrees tilt is plenty, 20 mm rise and fall will do a lot too: so your lens should do fine.