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PostPosted: Tue Oct 19, 2010 6:16 pm 
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Location: Chicago, IL USA
I'm a bit of a novice when it comes to DSLR photography terminology-wise, so pardon the awkward use of language.

I have a Nikon D5000 with a Nikkor 105 mm macro lens which does all of its focusing internally (i.e. the barrel doesn't extend).

I just got a Sony a55 with a Sigma EX 105 mm macro lens that extends like a zoom lens when in use.

My questions:

[1] is there a Macro lens for the Sony similar to the Nikkor in terms of this behavior.
[2] is there any advantage of one type of lens architecture over the other?

Thanks for your thoughts!


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PostPosted: Tue Oct 19, 2010 6:48 pm 
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On 1, I'm not familiar with the current Sony range, but if you include 3rd party on Alpha mount then the Sigma 180mm is fixed length.

On 2, I believe extending lenses are simpler to design, as it largely works with any lens macro or not. If you add extension tubes to any lens to move it further out, you focus closer and have higher magnification. The advantage is when not in use, I think they'll be smaller on average than a fixed length design of similar specification.

Now when using a macro, the working distance is important. If the camera body is in a constant position, the lens extending when focusing could possibly hit something nearby if you're not careful. With a fixed length lens that is not an issue.

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PostPosted: Tue Oct 19, 2010 8:50 pm 
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Thanks for that. I definitely am concerned about hitting something with the lens as it extends (which seems like an obvious problem when taking macro shots). I wasn't aware if this when I bought it.


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PostPosted: Wed Oct 20, 2010 5:42 am 
The Sigma 150, 180 and the new Tamron 60 f/2 don't extend when focusing. The Tamron is cropped sensor only. I think the Tamron 180 maintains its length as well but I'm not sure.

I don't think the extension would be a problem. For example if the lens has a working distance of 10cm, and you get as close as you can before acquiring focus, focusing to 1:1 will extend the lens but it should never hit your subject. The only problem is if you're taking a picture of something by shooting through some other obstacles like a fence or leaves.

My Nikon AF-S 60 does not extend but has one of smallest working distances of any macro. It helps that the length is predictable and constant but I've never had any issues hitting anything, so I don't think any of the extending lenses will either. I don't shoot bugs so often though, and the big lens moving in on them might change things. :)


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