View Full Version : Regarding Wide Angle Rectilinears

Neil Purling
29-Jun-2008, 06:48
I have amassed a small collection of these and intend to use some, or all of them on my 4x5 Graphic.
I do not know precisely how far down one ought to stop down for best definition, but at some point definition is compromised by diffraction anyway.
Lge format lenses seem to reach their best definition about four stops down from whatever is wide-open. I may be completely wrong but what are your findings?
The only one I have mounted at the moment is a no-name 4". I have shot at f16, which is wide open of course and at f32. I was a going to have the negs scanned and printed.

Ole Tjugen
29-Jun-2008, 07:40
The central definition will be limited by diffraction, but the peripheral definition continues to improve as you stop down. F:32 seems like a good starting point for a 4" WA Rectilinear on 4x5".

This is where I see a clear difference between Rectilinears and Aplanats: The field flatness of wide angle Aplanats is far superior to what I have seen from Rectilinears, so you can generally get away with larger stops. I have used a 150mm WA Aplanat at f:32 on 24x30cm, and the corner definition there seems to me to be significantly better than with a 3 1/4" WA Rectilinear on 4x5" at f:45.

Neil Purling
29-Jun-2008, 07:49
W.A. Rectilinear or W.A.Aplanat, surely they are the same optical design?
Maybe the ones you have are by better makers?
I have just had a look at ten sheets I shot yesterday at a steam & vintage rally on a farm near me. I took my latest acquisition, the 4" WAR
Behind a nice Burrell traction engine belted up to a Ransomes threshing drum I found a decaying railway van body. I shot the van at f16 and f32.
The film was Maco print film. At 3ASA this meant 8s @ f32 or 2s @ f16.
These negatives look tasty.

Ole Tjugen
29-Jun-2008, 08:53
"Common knowledge" is that Rectilinears and Aplanats are the same design. I'm not so convinced any longer, and especially not at the wide end. The WA Aplanats tend to be closer spaced, and have thicker glasses than the WA Rectilinears.

Glenn Thoreson
30-Jun-2008, 11:46
I would stop down any RR to improve the corner definition. Stop it down good. I don't think I'd worry about diffraction on the center portion. These things are scary sharp in the center anyway.

Neil Purling
30-Jun-2008, 12:14
These are the only two W.A.R. lenses that I have mounted, and the one in the silver panel sits in a Copal #0 hole which is far too large.
The lens in the silver panel is a no-name 100mm that I have shot with. The black panel lens is marked "IXL Extreme Wide Angle 6 1/2 X 8 1/2". It came back from SKG this morning so I haven't shot with it yet.

Neil Purling
30-Jun-2008, 12:46
This is one of the 'scrap' negatives. I took the scissors to it and scanned a slice.
I don't have a film scanner capable of dealing with the whole 4x5 negative.
This was taken on Saturday with the little 100mm. Exposure was 8s @ f32, so the drive belt to the threshing drum has disappeared because it was flapping about.

Glenn Thoreson
1-Jul-2008, 15:57
Not bad. I would really like to see the whole thing. How did the corners turn out?

Neil Purling
1-Jul-2008, 23:16
In my book Photographic Lenses by Conrad Beck they do not print a astigmatism diagram for a Wide-Angle Rectilinear, nor do they suggest what aperture is the best to use for the best results across the frame.
My lens is anonymous, of unknown quality so I am playing with it at present till I can find the best aperture. I look along a imaginary line drawn across the frame, through the very centre and play with apertures to get the edge as good as possible. The very corners of the frame are probably going to be less impressive.

In the scan of the traction engine it is a 35mm frame sized piece.
If I had printed up the whole 4x5 negative what sort of size would the print be?