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01/17/2006 07:02:32 PM · #1 |
In reference to this thread, I would like to explore this topic a little more.
Originally posted by nshapiro:
Before you decide to send that on, you might consider that you could reverse that lens in front of your lenses on the EOS-20D, using a reversing ring coupler, and make it into a closeup lens. |
That's interesting Neil. Hadn't considered that. I'm just beginning to learn about how to do that. However, I'm a woman of my word, and I've already promised that camera to someone.
I am curious as to the practicality of reverse mounting old screw mount lenses onto my 20D, as well as my current lenses. And are other brands of lenses compatible for this?
Surely, this has been discussed, but I don't recall having seen it recently. |
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01/17/2006 07:19:38 PM · #2 |
| This is something I'm interetsed in too, anyone? |
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01/17/2006 07:26:55 PM · #3 |
This is what you can possibly do with a reverse ring. Notice that a Canon Powershot A70 was used with an attached reversed Yashica ML50mm f/1.9 SLR Lens.
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01/17/2006 07:29:33 PM · #4 |
The best lenses to use for reversing are the fast 50mm lenses. They give good results and have a physical aperture large enough to work on many lenses without vignetting, at least too much. Best part is, they're usually cheap. There's no limit on which brand of lens is usable, as long as it can be reverse mounted, but as with any optical system, a better lens will give better results. Old manual-focus 50mm lenses can be less than $50, but a "fast" lens is required, because you need the large aperture. The lens you mount onto should not have too large a front element, and the focal length should be 50mm or greater, 100mm works wonderfully. a 100/2.8 lens and a 50/1.4 lens (reversed) are a great pair.
You need a reversing ring of the proper size, but you can experiment by just holding things together if you're careful not to bump against the front element of your main lens.
Try a 50mm lens reversed on a lens of about 100mm focal length, the increase in magnification will be amazing. Finding the focus point is the biggest issue. It's only an inch or so from the lens, and you can't do much to change it. That's the limiting aspect of this technique.
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01/17/2006 07:33:51 PM · #5 |
Found you an article on the web. Maybe not the best, but pretty good for a quick search:
Macro Photography
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01/17/2006 07:45:23 PM · #6 |
Originally posted by kirbic:
You need a reversing ring of the proper size, but you can experiment by just holding things together if you're careful not to bump against the front element of your main lens.
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Hi kirbic
I think that technique is referred to as coupling, (or stacking), whereas reversing is more often just attaching a reversed lens directly to the body.
A different adapter ring is required for each technique.
Reversing a 50mm prime will give a useful 1:1 magnification for macros whereas coupling can give much higher magnifications.
Th magnification can be calculated for coupled lenses with the formula :
Magnification = Focal length of primary lens/ focal length of coupled lens.
bazz. |
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01/17/2006 07:51:09 PM · #7 |
| This is all fascinating. My question is: Would I be able to do this with my current lenses? |
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01/17/2006 07:55:56 PM · #8 |
Originally posted by greatandsmall:
This is all fascinating. My question is: Would I be able to do this with my current lenses? |
If you had a fast 50mm lens, you could potentially reverse it onto the 75-300.
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01/17/2006 08:04:57 PM · #9 |
Originally posted by sir_bazz:
Originally posted by kirbic:
You need a reversing ring of the proper size, but you can experiment by just holding things together if you're careful not to bump against the front element of your main lens.
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Hi kirbic
I think that technique is referred to as coupling, (or stacking), whereas reversing is more often just attaching a reversed lens directly to the body.
A different adapter ring is required for each technique.
Reversing a 50mm prime will give a useful 1:1 magnification for macros whereas coupling can give much higher magnifications.
Th magnification can be calculated for coupled lenses with the formula :
Magnification = Focal length of primary lens/ focal length of coupled lens.
bazz. |
Yes, actually I meant to say "coupling ring." A reversing setup is different, and not something many folks use, since it's as expensive as a macro lens.
The available magnification for a 50mm reversed onto a Canon 100mm macro is about 2.8:1. The formula often given for the final magnification ignores the "starting magnification" of the main lens. In the case of this example, the magnification is M+Y/X where M is the magnification of the camera lens (1 in the case of the 100 macro), Y is the focal length of the normally mounted lens, and X is the focal length of the reverse-coupled lens. This should give 1+(100/50)=3, and we see a bit less because the Canon 100 macro has a somewhat shorter focal length at full magnification.
So, if we put a 50mm reversed on a 200mm lens, where the 200mm lens has a maximum magnification of 0.3x, the total magnification will be 0.3+(200/50) = 4.3x
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01/17/2006 08:12:34 PM · #10 |
Originally posted by kirbic:
In the case of this example, the magnification is M+Y/X where M is the magnification of the camera lens (1 in the case of the 100 macro), Y is the focal length of the normally mounted lens, and X is the focal length of the reverse-coupled lens. This should give 1+(100/50)=3, and we see a bit less because the Canon 100 macro has a somewhat shorter focal length at full magnification.
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Thanks for that.
Now I understand how to calculate it for my macro lens as well. :)
cheers,
bazz. |
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01/18/2006 06:20:04 AM · #11 |
How does one focus with such a system ?
thanks,
P |
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01/18/2006 07:03:02 AM · #12 |
With difficulty, I found it easier to move the subject than the camera when doing some extreme reversed lens macro for my photo-a-day
50mm F1.8 reversed on 75-300 IS USM @ 300mm
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