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PostPosted: Sat Oct 18, 2008 1:10 pm 
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Posts: 8022
Location: UK
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Long lens is long. In my package today I got a reversing ring. This has filter threads on both sides, and allows you to join two lenses together.

Going from left to right are the following:
Sony A350
Tamron 28-300mm lens at 300mm
72-62 step down ring
62-67 step up ring
67-58 reversing ring
Olympus Zuiko 70-300mm lens at 70mm

The theory goes along that magnification of the two lenses is equal to the focal length of the normally connected lens, divided by the focal length of the reversed lens. In this case that is approximately 300/70 = 4.3x.

I wanted to use other lenses, but I can't currently use any Sony mount lenses reversed as the aperture is sprung loaded to smallest size. The other Oly lens is wide but again the physical aperture is too small. So the 70-300 is the only one I have to use at the moment in reversed mode. But with that even at minimum, it means the normal lens needs to be over 70mm to have any magnification, so I went with my longest lens.

So I tested it as I usually do for macro by photographing a ruler. Following pic is full image resized.

Image

Each bigger division is 1mm, with additional marks at 0.5mm. So we have a minimum visible width of just over 5.5mm. Compared to the sensor width, this gives an actual magnification of around 4x. Close enough to theory.

Image

What about the quality? Above is a 100% crop from the middle of the ruler test. Note there is slight blurring and faint CA. It gets worse at the edges. I did take multiple photos to check this.

Image

For something a little more interesting, I grabbed a pin I had nearby. According to the package it came in, the pin is 0.6mm in diameter.

Image

And again a 100% crop showing softness.

To me this was just a quick proof of concept. Next is to look at a lens combination that might give better results. I've read elsewhere that zoom lenses don't work well as the reversed lens. My next step will be to find a way to get the Sony lenses to lock in wide aperture position and try them.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Sat Oct 18, 2008 8:31 pm 
Interesting.

I have been wondering whether it would be possible/doable to use two zoom lenses this way and not use any primes. I'm particularly interested in the result when using the two Olympus kit lenses. If you would put the 14-42 at 14mm reversed on a 40-150 at 150mm the magnification should be 150/14=10,7x :shock:.

I don't see the 40-150 in your signature so you may not have it. I also don't know whether you can fit them reversed with the ring(s) you have but if you do and it can be mounted this way I'd be interested in hearing/seeing the results.

Could you elaborate a bit on the aperture issue you mentioned? What is exactly the reason you didn't/couldn't use the other Olympus lens here?

I'd also like to see more photos you have taken/will take with the setup shown here. Something a bit more photogenic than a ruler or a pin. ;)

Ben
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When in doubt..... Press the shutter.


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PostPosted: Sat Oct 18, 2008 8:59 pm 
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You don't get something for nothing. Might be 10x magnification, but I wouldn't be surprised if it's 10x less light too. Also the quality may suffer... if this was easy, why do we not see everyone make greater than 1x magnification macro zooms? As far as I'm aware only Canon does and they're certainly not cheap.

I wasn't happy with the quality as it currently stands so I didn't try any more images. Also, the standard macro problems are ever present, only more so. I wonder if the physics work like a teleconverter. That is, does the effective aperture drop with increasing focal length? If so, then that combo might have been equivalent to 1200mm f/22 or f/32 as I was setting the 300mm between f/5.6 to f/8 and even higher. I don't think the reversed lens affects it as long as it's wide enough not to vignette. The light going through certainly didn't seem that high and I had to use relatively long exposures. Not to mention the DoF... more like what DoF? The practical DoF must have been a fraction of a mm.

The aperture issue is simply the circle of light the reversed lens let through. I did start with the 14-42, but that let through a tiny circle even when wide open. That's why I switched to the 70-300 as its aperture was bigger. Note in this sense, I'm talking absolute diameter. Look through the lens. I think the best (relatively cheap) lens for the reversed end might be one of the 50mm f/1.x types, providing you have a long enough one normally to get the magnification up.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Sat Oct 18, 2008 11:17 pm 
Although it will be interesting/fun to experiment with such extreme magnifications it is indeed likely to be very limited in many ways and I would be happy with anything close to 1:1 or better. The 14-42 lens gives 1:4,1 at 20cm min. focus distance so that would be a significant improvement. Both lenses at the 40/42mm focal length should generate such a near 1:1 magnification.

Have you tried both lenses at 70mm? With the Tamron even shorter you should get even lower magnifications but probably gain light.

And what happens if you mount them the other way around on the E-510? Both at their widest focal length you would get 70/28=2.5x But they would both be able to use their widest aperture. Or do the Tamron lenses also have a spring on the aperture? Is it part of how Sony cameras control the aperture and not just on Sony's own lenses?

Ben
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When in doubt..... Press the shutter.


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PostPosted: Sat Oct 18, 2008 11:42 pm 
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I think the sprung aperture is a quirk/feature of alpha mount. All my Tamrons do it too.

Didn't try for 1:1 as I have a dedicated lens for that already. The only reason for me to try the reversing ring is to go beyond that.

Will try the two Olys assuming I have a converter ring set to match, but I don't think I can go to 58mm twice with what I have. I standardised on 62mm as that is the size on my main lens on the Sony.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Sat Apr 18, 2009 11:26 pm 
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Joined: Thu Apr 02, 2009 9:03 am
Posts: 854
Location: Paris, London
A good read, thanks for posting it. Think I will avoid this way of getting more magnification.


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PostPosted: Fri Nov 22, 2013 6:06 am 
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Joined: Fri Nov 22, 2013 5:34 am
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I smashed my 18/55 canon lens when I dropped my camera so I bought a reversing ring to try it and see. It does work well but not outdoors in a controlled environment its not bad but outside it takes to long to get all set up and by the time you do the bug is gone. I like my macro tubes and my 18/270 tamron I know its not a macro lens but it works pretty dam good. kelly


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