Jan. 2002
President's
Message
Photo FAQs
Photo FAQs
Eric Kissa
Q.:Can
the image size in close-up photography be increased by reversing the lens?
A.:A
lens is sometimes reversed in close-up photography (the front of the lens
towards the camera) for two reasons: (a) to get a larger image and working
distance, and (b) to improve the optical performance. The lenses, other
than true macro lenses, are designed for making images much smaller than
the real size of the subject. In macrophotography the image on film is
larger than the real size of the subject and the lens should be turned
around. Reversing the lens requires two accessories: (a) a reversing ring
which screws into the threads on the front of the lens and has a bayonet
mount on the other end for attaching the lens to the camera, and (b) a
ring for operating the automatic diaphragm of the lens with a double cable
release. The second ring can be omitted by manually opening the diaphragm
for composing and closing the diaphragm for the exposure.
Reversing the lens changes the distance between optical center of the
lens and the film. Firstly, the reversing ring increases this distance.
Secondly, with short focal length lenses the distance between the front
glass surface and the end of filter threads becomes a significant additional
extension and the magnification increases accordingly. With some short
focal length lenses (20-24mm) an image larger than life size can be achieved.
However, with some long focal length lenses the reversal of the optics
may actually decrease the extension and lower the magnification. Another
reason for reversing only short focal length lenses is the mechanical
stress on the lens. Because the front of the lens has to carry the weight
of the lens, the lens reversal technique is suitable mainly for short
focal length lenses with a non-rotating front element.
Q.:I am interested in the Nikkor 35mm f/2.0 D AF, but I have seen a lot of reports about problems where the iris blades hung up or simply quit operating. Is this a real issue, and if so, was it ever resolved by Nikon?
A.:Unfortunately,
the issue seems to be real. The 35mm f/2.0 D autofocus lens I have used
for less than two years has a sticking diaphragm. I mailed it to Nikon.
The repair will take one month and cost $ 159, about half of the amount
I paid for the new lens. The repaired lens will have only a 6 month warranty.
As far as the second part of your question is concerned, Nikon has told
me that this lens has no unusual problems and is well liked by the customers.
The manual focus 35mm f/2.0 Nikkor was a reliable lens popular with photojournalists
for its focal length and optical performance.
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Send questions concerning photographic
equipment (cameras, lenses, accessories, filters), photographic techniques
(other than digital), and film, as well as information on international
photographic exhibitions, to: ekissa @aol.com.