Hazed But Not Fazed
e6filmuser
Registered Users Posts: 3,378 Major grins
Having invested in a Schneider HM 40mm enlarger lens, which is supposed to give very high performance, I have been extremely frustrated by an ill-defined, but image-ruining, whitish haze just off-centre. Associated with this, I have noticed a similar effect through the viewfinder. This was all (at least) with a FOV of 11mm down to 5mm.
This reminded me of the well-know problem with the film macro lens Tamron SP 90mm f2.5 when used on digital cameras. That gives a dark aperture-shaped area in the middle of the image. This was due to light bouncing between the flat surface of the sensor and the flat surface of the rear element of the lens. (Look up lasers!).
This was overcome by attaching a matching TC with its curved rear surface eliminating the effect.
The problem I was getting, with flash and the lens set at f11 or f16 is illustrated by the first two images.
I solved this by putting a high quality TC (Kiron Matchmate x 1.5) in the setup but wanted to keep the Schneider as the only glass in the setup. I seemed that a small change in the plane of the rear of the lens and that of the sensor should work. So I put a tilt adapter (OM to m4/3) in the setup and gave it a small angle of tilt (for this purpose it doesn't matter, for most subjects, in which direction) and obtained an instant improvement (third image). This is a problem of the reversed lens. The surface the rear element of the lens is very convex but the front is unusually flat.
There is a limited choice of tilt adapters. Mine tilts nicely but is difficult to remove from the camera flange. It works perfectly with my cheap m4/3 tubes, which work fairly well with the camera flange. So I have glued it into a 15mm one so that I cannot, in haste, get it stuck in the camera.
I hope this helps someone.
Harold
This reminded me of the well-know problem with the film macro lens Tamron SP 90mm f2.5 when used on digital cameras. That gives a dark aperture-shaped area in the middle of the image. This was due to light bouncing between the flat surface of the sensor and the flat surface of the rear element of the lens. (Look up lasers!).
This was overcome by attaching a matching TC with its curved rear surface eliminating the effect.
The problem I was getting, with flash and the lens set at f11 or f16 is illustrated by the first two images.
I solved this by putting a high quality TC (Kiron Matchmate x 1.5) in the setup but wanted to keep the Schneider as the only glass in the setup. I seemed that a small change in the plane of the rear of the lens and that of the sensor should work. So I put a tilt adapter (OM to m4/3) in the setup and gave it a small angle of tilt (for this purpose it doesn't matter, for most subjects, in which direction) and obtained an instant improvement (third image). This is a problem of the reversed lens. The surface the rear element of the lens is very convex but the front is unusually flat.
There is a limited choice of tilt adapters. Mine tilts nicely but is difficult to remove from the camera flange. It works perfectly with my cheap m4/3 tubes, which work fairly well with the camera flange. So I have glued it into a 15mm one so that I cannot, in haste, get it stuck in the camera.
I hope this helps someone.
Harold
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Brian V.
http://www.flickr.com/photos/lordv/
http://www.lordv.smugmug.com/
Thanks, Brian. Not affordable with my film cameras but the problem only arises with digital sensors. Another day, another problem solved. I am now wondering whether IS is causing problems with high magnification flash images.
Harold