Beef
Hi,
When I’ve been printing my film, I’ve sometimes noticed that some things I’d actually focused on weren’t quite as sharp as I’d set them to be when taking the shot.
There were two possible reasons: 1. The development process wasn’t correct. 2. Faults in the camera optics
. With SLR cameras, there are effectively two optical paths:
1. Through the lens -> via the mirror onto the focusing screen -> into the eye
2. Through the lens and directly onto the film (with the mirror raised)
. If you focus using the split-image indicator, it doesn’t necessarily mean that the image will hit the film in exactly the same way. Worn mechanics or tolerances in the finish (e.g. on the rail on which the film rests) can cause deviations (especially in 35mm format). I have often heard of these problems with SLR cameras and wanted to put my camera to the test.
I set up the following experiment for this purpose:
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I stretched a long, fine, black sewing thread across the floor (secured with sticky tape). Halfway along the length, I then stretched another thread at a right angle to it.
(At first I wanted to use a guitar cable, but that turned out to be too thick... please ignore that. I was just too lazy to take it down again :lol: )
You should use a lens with the longest possible focal length (here a 205mm telephoto) and zoom in as far as possible, as even the slightest deviations will affect the sharpness here.
I placed the camera on a tripod and set it as low as possible (for greater measurement accuracy).
Now, aim at the short thread lying across the frame in portrait orientation and use the cross-hairs to focus on it with as much sharpness as possible.
When taking the shot, the smallest aperture (i.e. the aperture fully open) must be used to achieve the shallowest possible depth of field.
I also used a cable release to prevent camera shake.
The result was this:
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You can clearly see (especially in the second image) that the intersection (i.e. the cross) is the most sharp point in the whole image.
From this, we can conclude: The camera is perfectly calibrated and the problem lay with the development or enlargement process.
As I realised afterwards, it was actually down to the developer, as it had simply run out :rolleyes: You can see that straight away from these dreadful pictures :lol:
Well, I’ve just posted this here in case anyone else here is questioning their camera :( After all, these discrepancies do actually exist.
Regards
Andi
KlausWehner
Hello everyone!
This is an important test that I would particularly recommend to all rangefinder camera photographers!
My setup looks like this:
Camera height on the tripod: 2m. From the base of the setup, a tape measure is laid out on the ground (length: 3m).
A mark is placed at the 2m mark – this makes it easier to focus using the rangefinder.
On the negatives developed later, you can read off the deviation from ideal sharpness very precisely using the scale.
But be careful! I know of a case where, following this test and a few complaints in Solms, the photographer is now ready to
sell his entire camera kit (including fast lenses) again.
No joke! Not for the faint-hearted!
The setup described above takes just a few minutes. Tests like this provide reassurance – one way or another. It’s
well worth it. I’m very keen to hear about further testing experiences...
Regards
Klaus
