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12-06-2010, 10:09 AM   #1
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Lens reversal tips

Wanted to get some opinions on a configuration for lens reversal...not wanting to spend any money, other than for the adapter ring. Just want to have some fun with an area of photography that I never thought I'd be interested in.

Here is what I have...I'd like to get some thoughts about what lens should be on the camera body, and what lens I should reverse.

Camera
K20D

Autofocus
Pentax 18-55 3.5-5.6 kit lens
Sigma 28-80 3.5-5.6 Macro

Manual Focus
Pentax-M 50mm 1.7
Sigma 70-210 4-5.6 UCII

I also have an off-brand magnifier that I can screw onto the front of a lens. Although I couldn't secure it, I was able to slide the magnifier over top of the outside of the M50 for a snug enough fit that I could focus. Would it be better to just get a step up adapter instead?

Looking forward to your replies...

12-06-2010, 10:20 AM   #2
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QuoteOriginally posted by gcoello Quote
Wanted to get some opinions on a configuration for lens reversal...not wanting to spend any money, other than for the adapter ring. Just want to have some fun with an area of photography that I never thought I'd be interested in.

Here is what I have...I'd like to get some thoughts about what lens should be on the camera body, and what lens I should reverse.

Camera
K20D

Autofocus
Pentax 18-55 3.5-5.6 kit lens
Sigma 28-80 3.5-5.6 Macro

Manual Focus
Pentax-M 50mm 1.7
Sigma 70-210 4-5.6 UCII

I also have an off-brand magnifier that I can screw onto the front of a lens. Although I couldn't secure it, I was able to slide the magnifier over top of the outside of the M50 for a snug enough fit that I could focus. Would it be better to just get a step up adapter instead?

Looking forward to your replies...
I would think you should try the 18-55 on the body with the 50 kissing it. It may not matter much what you set the aperture of the 50 to but you may as well use it open to send in as much light as you can. With the 18-55 on the body, at least your light metering will be much easier and can be controlled via the camera body.
You are not going to use any automatic focus with the lens or body so forget about that in the equation.
12-06-2010, 10:32 AM   #3
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I played with this concept to understand it some months ago. The best combo I found was with an older prime lens (I used a FA 50mm lens) that I could adjust the f-stop. It gave me plenty of magnification and a reasonable working distance from my subject. I did try the kit lens but no manual f-stop adjustment and the zoom get's in the way. I'd stick with your M-50mm.
12-06-2010, 12:56 PM   #4
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Reverse the 18-55. You don't have to attach any other lens. Fix the aperture lever using a match.

12-06-2010, 08:44 PM   #5
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If you want to reverse one lens to mount to the body only, then the 28-90 would be good. It has an adjustable aperture ring, does it not? I reverse mount a Pentax 28-90 often but find matching lens front to lens front less practical.
But your original post leads me to believe you are mounting lenses face to face. In which case I stand by my original suggestion of mounting one of the auto aperture lenses in proper mount to the body and then the front of the 50 to the front of the mounted lens.
There are many topics around the forum on both reversal rings and reverse adaptors.
12-06-2010, 09:37 PM   #6
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Before I fall asleep, here are the basics of lens reversal. There are two different ways: mount reversal, and stacking. With mount reversal, you use a ring with a PK mount on one side and threads to match your lens on the other. You just flip the lens around. But unless the objective has a deep inset, you won't get much magnification, just a very sharp and close image. MAGNIFICATION COMES FROM EXTENSION, NOT FROM REVERSAL. For more magnification, put some macro tubes behind the mount-reversal ring.

Stacking uses a thread reversal ring, or you can just tape two lenses together head-to-head. You can get extreme magnification this way. The lens mounted on your camera is called the primary; the lens reverse-stacked against it is called the secondary. The amount of magnification is their focal-length ratio. With a 105mm primary and a 35mm secondary, MAG= 105/35= 3x. With a 150mm primary and a 25mm secondary, MAG= 150/25= 6x. Remember that magnification eats light. Light loss is MAG+1 f-stops. At 1x, you lose 2 stops. At 6x, you lose 7 stops.

With either type of reversal, your working distance is REAL CLOSE -- it's the lens register (flange focal distance). With a Pentax compatible lens, that's ~45mm or a little under two inches. If you reverse a Leica screwmount lens, working distance is ~28mm or a little over one inch. And with either type of reversal, the reversed lens needs a manually controlled diaphragm. No FAJ's need apply. When stacking, adjust the secondary's aperture and leave the primary wide-open, else you'll get a vignetted circular image.

IMHO lens reversal is mostly for studio use, unless you've stacked a medium- or large-format lens as the secondary, for longer working distance. Many wee tiny subjects get very nervous about a big lens hanging an inch or two from their antennae. Of COURSE they get nervous -- wouldn't you? G'night now.
12-07-2010, 05:03 AM   #7
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QuoteOriginally posted by elho_cid Quote
Reverse the 18-55. You don't have to attach any other lens. Fix the aperture lever using a match.


The pvc tube shown allows one to adjust the aperture. Photos of lcd screen.
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