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06-23-2011, 08:56 PM   #1
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Do step up rings affect focal length of Raynox on DFA100mmWR?

Im still looking into ways of increasing the magnification for Macro photography, I currently have the DFA 100mm WR and was considering either the Raynox DCR-250 or the Vivitar 2x macro teleconverter, but notice the Raynox is for lenses of 52mm mount, but the DFA 100 is 49mm:

will a step up ring affect the optics noticeably?

06-23-2011, 10:10 PM   #2
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QuoteOriginally posted by JayR Quote
will a step up ring affect the optics noticeably?
Noticeably: No.
Very slightly: Yes.

I often use the +8 dioptre DCR-250 with a 49-52 step ring on my 49mm primes; the ring thickness doesn't seem to matter. But those primes have shallow insets. I'm not sure if your DFA100 has a shallow or deep inset. Well, I can't find my Raynox kit right now (I'm still unpacking gear from a long journey) but I put a +10 dioptre closeup adapter onto my MacTak 50/4, which *does* have a deep inset, about 50mm. I checked the focus on some text. Then I handheld the closeup lens a bit further from the MacTak -- actually, I held the closeup lens constant re: the text, and pulled the camera back. I could move it about another 50mm before I started getting vignetting. Magnification did not appear to change.

I substituted a ruler for the text. With the MacTak fully extended to 1:1, it sees ~23mm, as expected. With the +10 dioptre lens attached, it sees ~16mm, so magnification increased to ~1.34:1. The +8 dioptre Raynox DCR-250 will give a bit less magnification. (The 2x TC would take you into 2:1 territory, but with a severe loss of light.) I then tried pulling the camera away from the closeup adapter, and magnification seemed to decrease very slightly -- hard to tell for sure, what with shadows, my shaky hands, and the perversity of inanimate objects.

Short answer: Don't sweat it!

Last edited by RioRico; 06-23-2011 at 10:36 PM.
06-23-2011, 10:11 PM   #3
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The Raynox DCR-250 comes with a spring-loaded adapter that snaps onto almost any lens. The adapter doesn't affect the focal length but you do need to be a little careful to center it as you snap it on your lens, otherwise you can get an unintended tilt-shift sort of effect.

I think you'd make a good choice with the DCR-250 to get more magnification from your DFA 100. IQ may suffer a bit at the edges but should still be sharp in the center. I use the DCR-150 with other lenses and like it. It's an inexpensive and very flexible macro solution.

Note that I have no basis of comparison of the Raynox DCR vs. Vivitar TC.
06-23-2011, 10:36 PM   #4
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QuoteOriginally posted by DeadJohn Quote
The Raynox DCR-250 comes with a spring-loaded adapter that snaps onto almost any lens.
Aha, I just found my Raynox kit! (Spare rings, adapters, etc.) The springy adapter is rated for 52-67mm. It *can* be force-fit onto a 49mm thread, but that's inelegant, any maybe risky. A 49-43 stepdown ring lets me thread the Raynox directly onto a 49mm thread lens. (I used a 49-52 ring with the springy adapter before I got the 49-43.) I just mounted that on the MacTak 50 and it 'sees' ~18mm on the ruler. So magnification went from 1:1 to ~1.25:1, ie not a whole helluva lot.

EDIT: I just snapped the Raynox in its springy adapter onto my Vivitar-Komine 90/2.8 macro, which has an inset of ~20mm. Without the Raynox, the lens sees ~23mm on the ruler. With the Raynox, it sees ~12mm. So magnification goes from 1:1 to 2:1 at that focal length. Yeah, that is worth it!


Last edited by RioRico; 06-23-2011 at 10:44 PM.
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