I was curious to know the coverage of Kodak Wide Field Ektar, for the 250mm f6.3 lens. I know it is listed as covering 85 degrees, and other threads on this site indicate it will cover 11x14 and even 14x17. I wanted to know if someone might know the exact coverage in millimeters, so I would know how much room to spare I would have with my 11x14. Thanks.
I have it listed as a 422 IC
The list compiled by Michael Gudzinowicz and linked from the home page here lists the coverage circle at 422mm.
http://www.largeformatphotography.info/lenseslist.html
One person says 422 mm and others repeat that value and it becomes the gospel truth. I wonder where that value came from? Does anyone have a citation to a Kodak publication? Or a measurement? Are you sure that the value isn't 421 or 423 mm?
80 degrees and 250 mm focal length would give 420 mm.
The Kodak publication "Camera Technique for Professional Photographers" has a datasheet for the Wide Field Ektars. All that it says about coverage is that the maximum recommended negative size is 11x14 in. without camera swings and 8x10 in. using camera swings.
John,
You can find EKC's specs at: http://www.cameraeccentric.com/html/info/kodakektar/ektar59.html
The data is for lenses focused at infinity or 6 feet, wide open or at f/16. The numbers I used are for f/22. I don't recall the exact source - either a magazine review of specs or a lens design text or both - but they are consistent.
For DOF calculations, EKC uses 2 min arc for the COC which they indicate is approximately 1/1720 of the focal length. For a 250 mm lens, that would be 0.145 mm or approx. 7 lpmm. They indicate there's some flexibility for enlargement. I'd assume they use the same criteria for the coverage circle specs.
Coverage of 14x17 might be possible, however, I'd advise you to contact anyone posting the info to ask for details - distance focused upon, printing process and paper, corner sharpness criteria, and f/stop.
I looked at the specs and was very encouraged in this regard when I acquired my 250mm Wide Field Ektar. However, I find that I run out of coverage pretty quickly with 8x10 even at f32 so I find myself being exceptionally careful in this regard. I have not even attempted to use it on 11x14 since I have a 240mm Computar that fits the billing quite admirably and with less concern on my part. Would be interested in hearing if you can in fact produce an 11x14 photograph with this lens.
Some lens manufacturers like Nikon maintain a highly conservative published circle of illumination. Others appear to take it right out to the edge as I feel may be the case here.
Cheers!
I'm still looking for someone who can tell me the coverage of a 21 1/4" Ektanon before I put it into a shutter. I was hoping to use it on an 8x20. I can't seem to find much literature on this Kodak lens either.
Robert:
I was thinking about one of those devices that hold barrel lenses of various diameters in place so you could put this lens on a board and physically get it on your camera to verify that it will in fact cover 8x20 and then by how much? That is the only condition that I would consider allocating a shutter and the investment in custom machining to accomplish said objective.
Actually, I made a mistake on my original post; I stated a previous thread indicated the lens had coverage up to 14x17; that should have been 7x17. Thanks.
I personally have used a 250mm WFEktar on 7x17. I stopped down to f/32 or f/45. The effect in the corners was the same. The images I took were sharp enough for contact print work. If I deployed a little rise, the corner image would "pull" a little and elongate the scene. But it was still acceptably sharp (again, for contact print work).
I hope this helps.
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