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05-14-2012, 01:19 PM   #16
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QuoteOriginally posted by audiobomber Quote
The 18-135 is definitely an IF lens (focal length decreases at focus distances below infinity).

Sorry d4vr0s, I didn't get around to checking for vignetting. Lots going on, I'll try tomorrow.
Here are the full test results. The subject was an AAA battery: https://picasaweb.google.com/bonhommed/DA18135Raynox?authkey=Gv1sRgCKC6sMfl4trLnQE#

From these results, you can see why I don't carry a Raynox adapter with the 18-135mm. The Raynox 250 is severely compromised due to vignetting and the bare 18-135 can easily be cropped to the same FOV as you can achieve with the Raynox 150. A crop will have no vignetting and more DOF, but of course, fewer pixels.

Minimum focus distance is not recommended with an IF lens and Raynox. The IF design of the lens causes the focal length to decrease such that you actually lose magnification below infinity focus. Vignetting at MFD becomes horrific. For anyone who didn't click on the full test, these images are pretty representative of the achievable results:

18-135 at minimum focus distance:


18-135 with Raynox 150, infinity focus:


18-135 with Raynox 250, infinity focus:



Last edited by audiobomber; 07-02-2014 at 11:53 AM.
05-14-2012, 04:55 PM   #17
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Thank you audiobomber! I had no idea how badly IF might compromise the utility of a close-up lens.

Consider a pure IF lens (ie. the distance from lens to image is constant) of focal length f' cranked out to an initial mag m'. The new focal length is f'/(1+m').

If a close-up lens of focal length f" is added, the new magnification is:

m" = (f'/f")/(1+m')

the (1+m') term on the bottom is greater than one so always decreases m"

In practical terms this means that it doesn't help magnification to extend a purely IF lens with a close-up lens on it. It isn't quite true in real life because IF lenses often have the effective rear of the lens move with respect to the image plane.

Dave in Iowa

Last edited by newarts; 05-15-2012 at 06:47 AM.
05-14-2012, 06:44 PM   #18
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QuoteOriginally posted by newarts Quote
In practical terms this means that it doesn't help magnification to extend a purely IF lens with a close-up lens on it. It isn't quite true in real life because IF lenses often have the effective rear of the lens move with respect to the image plane.
I know the DA 18-250 behaves the same way with a Raynox mounted. It loses enough focal length at the minimum focus distance that the magnification is significantly lower than at infinity focus.

Last edited by audiobomber; 05-15-2012 at 03:27 PM.
05-15-2012, 02:28 PM   #19
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Thank you audiobomber, that's an awesome demonstration! Your test shots have been very helpful, I think I'll hold off on the Raynox for now.

05-15-2012, 03:32 PM   #20
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QuoteOriginally posted by RioRico Quote
OOPS! I GOOFED!! MEA CULPA!!!

I've corrected the above entry. I *DO* see vignetting with the DA18-250 -- I was thinking of using the DCR-250 on my FA100-300. Brain fart! I heartily apologize.
The Tamron/Pentax 18-250 works extremely well with the Raynox 150. Just set the lens on infinity focus and zoom to 250mm. IIRC, you will not see any vignetting at all when used like this. You can reduce the focal length for lower magnification. The Raynox 250 and 18-250 don't play well together, nor does the 250 and 55-300.

My light/casual kit for a couple of years was the 18-250, FA 35mm and Raynox 150.

Last edited by audiobomber; 05-15-2012 at 03:37 PM.
05-18-2012, 02:59 AM   #21
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Got the DCR150 and it shows vignetting when being combined with the DA18-135 and can only be used at 135mm. However, the vignetting can be removed easily in LR. With my Sigma 70-300 I have no vignetting at all focal lengths.
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