Satish Kumar wrote:
> Hi PUG�s,
>
> 1. What magnification is obtained when
>
> A. I use a reversing ring on a Normal Lens, Zoom Lens, Tele Lens & Wide Angle?
> B. I mate either of the two above lenses Back to Face in all possible
>combinations?
> C. I mate either of the two above lenses Face to Face in all possible
>combinations?
>
> 2. What are the merits & demerits?
>
Lens reversal is only appropriate when the magnification exceeds 1:1
(life size on the film).
Current AF macro lenses will reach 1:1 and the older ones gethalf way
there at 1:2 and you have to use extension tubes to get the rest of the way.
If you use thru the lens metering exposure compensation will take
care of itself unless you use a flash. If you have a flash system and camera
capable of TTL flash support it will still take care of itself. Prior to the auto
focus family
of pentax cameras only the LX and the Super program were able
to handle flash via TTL.
If you want a full run down on the tables, magnification, exposure compensation
etc. for a variety of lenses--- jump on ebay and buy a Carl Shipman book
on how to select and use Pentax SLR cameras. --- you can usually buy one
for under $15.00 and it contains all the information you ask.
Watch the age of the books--- as the books were published from 1977 to1990
in annual editions so it would be helpful to get one matching the age of your
equipment.
the basic problem is that lens reversal doesn't get you where you want to go
if macro photography is what you have in mind.
You first have to get extension--- via extension tubes, bellows, or
a special macro lens --- which have extra long helicoids in them for extension.--
as well as optical features to improve flatness of field which becomes very critical
in macro work because the depth of field disappears.
When you start 'magnification' of the image -beyond life size the exposure
compensation issues get clear out of hand and getting enough light becomes
a real problem. The object is also so close to the lense that a regular flash
doesn't do the trick---unless you have the ability to remove it from the camera
etc. Also the depth of field is so skinny at wide apertures as to be frustrating.
For example in photographing a bug you wind up having to decide which part
of the bug you want in focus.
A ring light is the solution for this.--- a special flash that screws into the lense
filter holder and has a range of a few inches. with heavy extension etc.
My favorite 'bug phtotoghphy' combination is a Super Program, with a 100 MM
SMC-A Macro lense plus extension tubes and a pentax ringlight. With fast film
I can stop down to f16 for improved depth of field (still not much). this works
well up to 1:1 (life sized on the negative).
Beyond that a fairly hard to find on the used market 'bellows A' has all the features
needed for additional extension and lens reversal. However it relies on a double
cable release
for lens automation which implies it works best on a camera that
will accept manual cable releases. Since flash is almost mandatory unless
you have studio lighting, and exposure compensation is difficult to calculate
the practical choices of cameras for the task is narrowed to the Super Program
and the LX as they are the models that have TTL flash support and will work with
a classic manual cable release.
>
> 3. How to calculate the aperture & shutter readings?
>
> 4. Is it possible to shoot without a Tripod, by using a faster film (>400ASA) &
>reduce shake?
>
> 5. What is the formula for calculating the magnification?
Magnification = Extension / focal length.
>
>
> Thanks a ton
>
> Satish Kumar
> Madras/India
>
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