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04-30-2014, 11:33 AM   #1
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Sigma 50mm f/2.8 EX DG macro functionality

I have a simple (?) question on how the Sigma 50mm f/2.8 EX DG macro lens operates. Could someone help me? I don't have this lens but I am considering it.

I read online and heard in Youtube videos that the lens has a floating front element. Does this mean I set the macro magnification by pulling out a built in extension tube? Then I assume I would focus using the focusing ring.

Or, do I turn the focusing ring enough to eventually engage the macro magnification extensions which push out the front element? Then I assume I would focus the image by mounting the camera on a focusing rail.

Thanks!

04-30-2014, 01:16 PM   #2
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Floating elements are just part of the lens design- they automatically move as you focus to ensure optimal sharpness. They're not something you otherwise interact with

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05-01-2014, 12:16 PM   #3
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Thanks for answering, Adam!
05-01-2014, 12:21 PM   #4
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It works the same way the manual focus version works, just with AF...

Sigma 50mm F2.8 Macro Lens Reviews - Sigma Lenses - Pentax Lens Review Database

https://www.flickr.com/search?user_id=38275020%40N00&sort=relevance&text=sigma%2050mm

05-01-2014, 05:20 PM   #5
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QuoteOriginally posted by 6BQ5 Quote
I read online and heard in Youtube videos that the lens has a floating front element. Does this mean I set the macro magnification by pulling out a built in extension tube? Then I assume I would focus using the focusing ring.
I has a floating internal focus system meaning that the lens groups change position relation to one another as the barrel extends to focus. There is a diagram somewhere online that shows how the relative position of the internal elements shift. To focus, you don't have to do anything special, just turn the ring or let the AF system do it for you. In terms of how the lens is in use, I have found it to be well made and a great shooter and my only real reservation is that the working distance at 1:1 is quite short. See my review (the 2nd oldest) in the lens review section (the pictured lens is mine) to see the short working distance.

Sigma 50mm F2.8 EX DG Macro Lens Reviews - Sigma Lenses - Pentax Lens Review Database

As for the relationship to the older non-AF versions...ummm...ummm...

BTW...you may want to make your decision soon. Sigma appears to be "shuffling" its current macro line.


Steve

Last edited by stevebrot; 05-01-2014 at 05:42 PM.
05-01-2014, 06:34 PM   #6
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Thanks for the reply, Steve! Yes, I saw the reviews here and on other sites. It seems like this is a very sharp lens and if you can accept the short working distance for macro shots then the IQ can be very, very good. I would be using this lens for film/slide duplication and processing. The working distance should be just fine and I'll have all sorts of tubes, holders, and adapters attached to the filter threads.

I was planning to buy this lens used - probably off of eBay. Isn't this lens discontinued already?
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