FIND A PHOTOGRAPHERForum and Galleries SUPPLIERS Forum and Galleries COURSES / HOLIDAYSForum and Galleries FEATURES Forum and Galleries JOBS Forum and Galleries SOCIALForum and Galleries ADVERTISING OPTIONS
Photographers.co.uk

Testing lenses the quick n' easy way

Okay testing lenses takes two routes, we can go down the mtf lines per millimetre direction using a proper test pattern ultra fine film or we can get a copy of the Venerable Sunday Times and several of those sticky notes and use them.

Find a double page spread in the times that doesn't have huge ads all over it especially at the edges, and pin the paper to a convenient wall at about waist high. Make sure its smooth and level. Now, put the camera on a tripod and get your adjustable flash ready. Make sure the film/sensor plane is parallel to newspaper on wall. We are going to take pictures of aforementioned newspaper of repute.

Put your lens on you want testing and moving the camera, don't use the zoom, ensure that the newspaper fills the frame. Then move in a bit cos' your viewfinder is going to clip the actual edges of the image and we don't want that. Now, focus really carefully, set the aperture to the widest you can, write the aperture and focal length on the sticky note and pin that on the newspaper, not in the centre or edges we need to see those bits later.

Now take your first shot, now refocus and take the second shot. Helps to eliminate focussing errors. I use a flash to light the paper cos at 1/5000 sec it eliminates all camera movement. Self timers or remotes are also handy.

Now, stop the lens down one stop, adjust your flash output and take another two shots remembering to refocus on the second shot. Continue until you run out of f-stops.

Now, for the fun part, the game is to be able to read the fine print of the newspaper at the edges of the image and compare them with the centre, then do the same with the ones taken stopped down. You should be able to see a marked improvement at the edges, as you stop the lens down a few stops from wide open.

It's best to use a Lupe if using negatives, that way you eliminate the effects of the resolution of the printing lens too.

So find the best f-stop that has the best edge and centre resolution. If you are using a zoom, set it at the widest setting first and do one run through, then at logical steps ie, 28mm, 35mm, 50mm, 70mm, 100mm etc.

This technique works best with slow film which has billions of grains to record fine detail.

This article was provided by David Butcher. David runs a number of photography courses at School of Photography.com. Please take a minute to take a look at what they have to offer.

This article is Copyright © School of Photography.com.



Return to the Help Centre

Testing photographic lenses