Press lens coverage and depth of fieldgreenspun.com : LUSENET : Large format photography : One Thread
As a new person to large format, I've purchased a relatively inexpensive camera lens combination to test the waters. The lens is an Ektar 127 (also have a 203). I do mostly landscape pictures and would like to produce the classic scene of a unique object(s) (flower, rock formation, etc.) in the foreground with a scenic backdrop (mountains, mesas, etc). As I would understand it, the ideal way to do this would be with a forward lens tilt to maximize DOF and small aperature. The problem would appear by my reading that the wider angle lens won't have good coverage. Is there a way around this without buying another lens? For example, does stopping down the aperature increase the coverage to any significant degree. And if so or not, how much tilt can I squeeze out of my lens. Is cropping a good option? I suppose I could do this through trial and error, but at the cost of film any help would be appreciated. Thanks.
-- Roger Rouch (email@example.com), June 02, 1999
You dont need to shoot any film to get an idea of the coverage of your lens. Just watch the ground glass as you swing and tilt. When you see the curved edge and darkening of the image you have found the limits for that lens. Check it at various apertures to see what it does.
-- tony brent (firstname.lastname@example.org), June 02, 1999.
Roger, you're getting ahead of yourself. Take the camera out, play with the focus, stop all the way down, develop the negative and see what you think. Your Ektar is a great lens but it isn't going to have the coverage for big movements; however you are going to need to get familiar with the new format before you play around too much with tilt anyway, particularly outside with changing light, wind, mosquitoes, spectators, etc. Keep things simple to start with. You will be able to get very nice - stunning, in fact - landscapes with no tilt on your 4x5 inch negative. If you are happy with your results and want to play around with tilts, you can spend the large pile of dough necessary to get a big image circle in that focal length.
Your 203 will have plenty of room for rise and tilts, by the way, and will make a nice landscape lens, too.
-- Erik Ryberg (email@example.com), June 03, 1999.
You can get the ground plane entirely in focus, from a flower a metre away all the way to infinity, even with a lens that has very limited coverage, by tilting the film plane. True, tilting the film plane rather than the lens will introduce false perspective, but that doesn't usually matter for landscapes.
As the others have pointed out, you can try this without burning film. Just use a dark cloth and loupe on the ground glass screen.
-- Alan Gibson (Alan.Gibson@technologist.com), June 03, 1999.
Imagine for a minute a sheet of film completely within an image circle of a lens, an Ektar 127mm for example. If the film is entirely within the image circle, tilting the lens will have NO adverse effect on coverage, that is to say that the film will still be entirely within the image circle.
-- Chad Jarvis (firstname.lastname@example.org), June 03, 1999.
This isnt quite true, Chad. As you tilt the lens, the optical axis shifts, as well, and you can run it off the film. You also need to drop (or raise) the lens to keep the optical axis centered on the film. But Chad is correct in the fact that if the lens covers the film with no movements, you should still get coverage with modest movements if you keep everything aligned. Also, keep in mind that the stated coverage circles are at infinity focus, which is worst case. Most shots are taken with the actual focal point closer than infinity, and the closer you focus, the larger your circle of coverage gets. I think you made a good decision in your modest start in large format. Even this combination will spoil you compared to medium or 35mm image quality.
-- Ron Shaw (email@example.com), June 03, 1999.
Just a bit of a follow up to my reply above. I used these same lenses on my Graphic View for many years for all kinds of photographs and never ran out of coverage for anything I needed to do -- from table top product pictures to "near and far" landscapes. They were both good sharp lenses with no bad habits that I was ever able to find. In fact I used the 203 on my 8 x 10 camera frequently to do lifesized or larger. As one gentleman mentioned, the longer you extend the lens, the bigger the coverage gets.
-- tony brent (firstname.lastname@example.org), June 03, 1999.
I wanted to say thanks for all of the suggestions. Sometimes the simplicity of the answers escapes me, and there were several simple ideas mentioned I can work with. One of which would be paying attention to the ground glass to tell the story. So far I have worked in rather low light, and the ground glass is a bit hard to see for good focus and dim edges. This I can work on as well. I can see that working with LF will be a little more challenging than my 35. I guess that's what makes it fun.
-- Roger Rouch (email@example.com), June 03, 1999.