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Old Feb 23, 2004, 6:16 PM   #1
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Default Reversing a lens Powershot A40

I want to reverse a olympus zuiko 50mm f/1,8 on a Powershot a40 to take super-macro foto's. Need advice. Do I need a bigger zoom to minimize vignetting?
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Old Mar 7, 2004, 9:59 PM   #2
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Is this the lens that you are talking about?
http://www.pbase.com/image/26713754
If it is, here are sample shots of this lens on an a40. These were shot quick just to show magnification (I uploaded them a long time ago) so I didn't put a lot of effort into geting good focus, lighting etc. I am using a 49mm-49mm macro ring and a 52mm to 49mm step ring. You could of course use a 49mm-52mm macro ring. You have to adjust you camera to full zoom to use it. Anything less than full zoom will vinyette with this lens. One shot is just the camera and the other is with the lens.
http://www.pbase.com/richardh/a40slrmacro
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Old Mar 8, 2004, 9:54 PM   #3
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Default Re: Reversing a lens Powershot A40

Quote:
Originally Posted by Bloodstrike
I want to reverse a olympus zuiko 50mm f/1,8 on a Powershot a40 to take super-macro foto's. Need advice. Do I need a bigger zoom to minimize vignetting?
Bigger zoom does help because it will reduce the chance of getting vignetting and increase magnification. However, consumer digicams usually have lower quality at the long zoom end unless you get a good camera with large zoom. As long as you can find an adapter of your A40 with a filter thread, you should be able to use your Zuiko 50mm F/1.8 See the following thread for more discussion and examples:
http://www.stevesforums.com/phpBB2/v...ic.php?t=15584

CK
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Old Mar 22, 2004, 12:48 PM   #4
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Thanx for the replies guys. I finally got my Zuiko. But I still don't have a lensadapter. So I must hold the lens in front of the A40. Only a piece of toilet-roll is preventing the lens from touching the Powershot A40.
No problem with vignetting. 3x zoom is enough. But I'm selling my A40 and my next digicam will be the G3. So I'll be using the Zuiko with the G3.

I have already experimented with the A40 and Zuiko. This is an example of my eye. Don't with tv and av-cable.

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Old Mar 22, 2004, 1:39 PM   #5
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Old Mar 22, 2004, 5:53 PM   #6
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I had thought of trying an eye picture but I never got around to it. This is the reversed lens? Any idea why the one photo makes it appear that there is a dry area on your eye surface?
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Old Mar 23, 2004, 4:35 AM   #7
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I finally got around to experimenting with a reversed lens. Not
the best lens, just a C-mount video camera wide-zoom lens. I
compared it to a Nikon 4T macro lens and to the native Oly C750 supermacro mode.

First difference -- the rather small diameter (49mm filter
thread) video camera lens had vignetting even at 10x.

One big difference was the working distance. The reversed lens
needed to be very close to the subject. Probably an inch or
less. The 4T was many inches away.

The next big difference was the magnification factor. The
reversed lens produced more magnification, and I discovered
that the shorter the focal length the greater the
magnification. Thus as I adjusted the lens from 75mm to 12.5mm
the magnification increased significantly.

But along with increased magnification the DOF became smaller
and more troublesome. It was very difficult to hold the camera
in focus. Now would stacking macro lenses produce the same
result as the reversed lens?

I'll try to have some images posted sometime tomorrow.
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Old Mar 23, 2004, 1:41 PM   #8
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Quote:
Originally Posted by Pooperdog
I had thought of trying an eye picture but I never got around to it. This is the reversed lens? Any idea why the one photo makes it appear that there is a dry area on your eye surface?
Which photo and area of my eye are referring to. The depht of field is very small, so in one photo the reflection in my eye is sharp and everything is blury. On the other photo the eyelashes. I think because those parts that are out of focus look dry.

The working distance of my lens is 2 inches. Digicam with bigger zoom gives
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Old Mar 23, 2004, 3:21 PM   #9
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I would like to think of a target subject that would work well to show both DOF and the magnification factor and be continuous so that unsteady camera holding is not an issue. Maybe that isn't possible.
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Old Mar 26, 2004, 8:11 AM   #10
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Ok, I finally have some test images up, but they don't really look too good. Hand holding the lens didn't help matters and it is a c-mount video camera lens rather than a 35mm SLR lens. I thought the lens had a 52mm filter thread but it was smaller than that so I didn't have a ring for it.

The set of images is from an Oly C750...

http://galt_57.home.att.net/macro.html
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