Lens testing.

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Mike Kennedy

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I want to thank the members who gave me tips on the best lenses for my new/old Pentax K1000.
At present I have 7, 42mm screw mount lenses and a "freebee" adaptor.Can anyone suggest a simple,inexpensive lens test I can do outdoors to select which of these lenses is the best?
I am not a scientist,I only play one on T.V.
Thanks All,
Mike
 
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One of the simplest ways is to make a lens test chart by finding a suitable flat vertical surface (wall, etc.) and taping 5 newspaper pages to it in an X pattern so that you have one in the center and one at each corner of your picture as viewed through your camera at a distance of 12 feet or so (the distance is arbitrary, 12 feet is just a compromise between close-up and distant). Photograph this on ISO 100 film or slower and then examine the results at a reasonable magnification (magnifying glass, loupe, slide projector, enlarger). You will immediately see whether the newspaper type is sharp or not. Expect reasonable sharpness at full aperture in the center, getting better at small apertures, and less good sharpness at the edge at full aperture, improving to almost or fully match the center at 3 to 4 stops smaller than maximum.
 

Bruce Appel

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What David said, just make sure you use a good solid tripod. Try and find a spot in open shade so that contrasty lighting doesn't confue things. I use a wall on the north side of my house. Shoot a series through each lens from wide open on down. You will find out which lenses perform best with your setup, and you will know at what apertures are best. Good stuff to know.
 

Ara Ghajanian

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Can you use a film scanner for viewing of the about test? I have a Nikon Coolscan dedicated film scanner.
 

rbarker

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I think it's helpful to start such exercises by defining what you want the test to accomplish, Mike. For example, do you want to find out which of your lenses provides the highest optical resolution? Or, alternatively, do you want to simply explore the characteristics of each lens at different apertures?

The choice of the "best" lens depends on the objectives for a specific image, and the conditions under which the image is being shot - not necessarily the optical resolution of the lens.
 

Eric Mac

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lens test

Another good one is the picket fence test. Focus on a marked fence post along the length of the fence (not straight at it) and shot it at various apertures. This will test depth of field, accuracy of focusing and as a bonus may give you an idea of the bokeh. Sometimes the lense may appear unsharp because the focusing is off.

Enjoy
Eric
 

Bruce Appel

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You can use a scanner. You may reach the limits of the scanner before you reach the limits of the lens and film though. Still should give you some useful information I would think.
The comment about focusing error is a good one. You need to be sure that the viewing screen is focusing to the same point as the film plane. Chances are it is, but if you have trouble getting sharp images it would be a good place to start looking.
 

Tom Duffy

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The standard target is the 1951 Air Force lens test chart. It's available from Edmund Scientific in Barrington, NJ. It's reasonably priced. I think there's more info in the APUG archive somewhere, but I'm too lazy to look...
 
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