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nikon el nikkor VS minolta rokkor

 
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SONYNUT



Joined: 22 Jan 2011
Posts: 635
Location: Minnesota USA

PostPosted: Mon Jan 24, 2011 5:09 am    Post subject: nikon el nikkor VS minolta rokkor Reply with quote

in reading all the stuff about infinity objectives on a telephoto lens..

I figured why not try my el nikkor that i used to use on a bellows..and stuck it on my rokkor 135mm





plus you have a very usable aperature on the el nikkor





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Last edited by SONYNUT on Tue Feb 15, 2011 1:05 pm; edited 1 time in total
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ChrisR
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Joined: 14 Mar 2009
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Location: Near London, UK

PostPosted: Mon Jan 24, 2011 6:33 am    Post subject: Reply with quote

You might expect to do better with the enlarger lens reversed, or perhaps a normal 50mm camera lens.
Camera lenses (unlike enlarger lenses) are designed to be used with subjects at infinity of course, so things "fit" if you use two, front against front.
I've had good results doing that, as well as some awful ones... Confused
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Mon Jan 24, 2011 8:44 am    Post subject: Reply with quote

SONYNUT, this is a common configuration often called a "lens combo". When the rear lens is at infinity focus, the magnification is just the ratio of the focal lengths (rear divided by front). Extending the rear lens increases the magnification. As ChrisR points out, it's generally better to reverse the front lens so as to maintain the focus relationship that the lens was designed for -- short distance on the "film" side of the lens. However, the difference is often not large enough to show up without pixel-peeping of carefully done comparison images.

By the way, combos have some interesting behavior of their own regarding aberrations and perspective. You might be interested in FAQ: Stopping down a lens combo.

--Rik
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Blame



Joined: 14 May 2010
Posts: 342

PostPosted: Mon Jan 24, 2011 9:52 am    Post subject: Reply with quote

rjlittlefield

I just followed up that link.

Now I understand what is happening with an objective + lens combo.

I knew that some zooms were not really working out, but I hadn't figured out the details.

Now I know why the same objective has different vignetting when mounted on different lenses. The rearmost lens inside the camera lens is small so with the light spreading out after being stopped down from the front, some misses it.

But did you know that some camera lenses are designed to stop down from the front?...well almost the front. I picked up what I am guessing is an early pentacon 200mm f/4, which is fully manual. The iris is towards the front of the lens. Here is a picture of one http://www.flickr.com/photos/awcam/5233653199/

200mm is not really short enough to test this out, but it might be interesting to see what other lenses stop down from the front.
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Charles Krebs



Joined: 01 Aug 2006
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Location: Issaquah, WA USA

PostPosted: Mon Jan 24, 2011 12:29 pm    Post subject: Reply with quote

Blame,

Olympus OM lenses also had front mounted aperture rings. But where is the aperture actually located (optically)... that is the real question.
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SONYNUT



Joined: 22 Jan 2011
Posts: 635
Location: Minnesota USA

PostPosted: Mon Jan 24, 2011 1:36 pm    Post subject: Reply with quote

with this set up i am not losing any focus or field by stopping down...but dof gain is good..

i'm not saying it is the best in the world..but if you have the parts you may as well use them
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Blame



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PostPosted: Tue Jan 25, 2011 8:16 am    Post subject: Reply with quote

Charles Krebs.

It is indeed. However I infer a sort of rule of thumb. Old camera lenses tended to hare smaller front lenses. That makes me think there has been a shift over the years from the front to the back.

The catch is that there has also been a shift towards better sharpness and flair control, at least if you are willing to pay for it.
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SONYNUT



Joined: 22 Jan 2011
Posts: 635
Location: Minnesota USA

PostPosted: Tue Feb 15, 2011 12:25 pm    Post subject: Reply with quote

Stuck the combo on my bellows...not to bad

single shot f8


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Last edited by SONYNUT on Tue Feb 15, 2011 1:08 pm; edited 1 time in total
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SONYNUT



Joined: 22 Jan 2011
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Location: Minnesota USA

PostPosted: Tue Feb 15, 2011 12:59 pm    Post subject: Reply with quote

as for reversing it...there is no difference...50mm doesn't change much(if anything it is worse with this el-nokor)...
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