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Sigma 18-50 mm F2.8 EX DC Macro lens for Nexus/Anthis


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#1 Deep6

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Posted 13 August 2007 - 06:13 PM

Sorry if I am a nag, but I see this lens pop up in underwater discussion for time to time without resolution for a Nexus housing. There is a tease on usanexus.com. They have not answered my two e-mail inquires. So, I put it to the gnomes and wizards of wetpixel.

I think it could be a good survey lens, e.g. I have never been on this dive site and have no idea what to shoot! In a dome port for a Nikon digital, it would be ~27 to 75 mm in 35 mm view or 36 to 100 mm in a flat port. While not a “real” macro lens, with the water magnification + .9 wet diopter, the flat port configuration is approaching 1:1.

My concerns are possible vineting in the flat port and fitting a zoom gear over the zoom lock. Has anyone tried this lens in a Nexus (Anthis) or Sea & Sea housing?

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#2 pakman

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Posted 13 August 2007 - 08:40 PM

I have the non macro version of that lens and I'm a big fan of it. It's a nice versatile lens... With the aperture stepped down, it shoots very well even at 18mm (much better on corners than the canon 10-22 IMHO).

I currently use it in a S&S housing with an Athena Dome and 40mm extension without an diopter. I wouldn't think of using it in a macro port!

But you might want to consider the 17-70mm DC Macro Sigma if you want that extra reach for macro. While it's not a EX lens, the quality of shots coming from that lens I've seen are as good as the 18-50 EX.

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#3 tkr

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Posted 14 August 2007 - 03:59 AM

I have been using the new 18-50 macro version quite a bit this year. I use it in a Sea & Sea housing with compact dome port and 40mm ring.
It appears to work well. I chose it over the 17-70 sigma, as it is a bit easier to house as the lens extention is not quite so large. I also thought it might work better optically. It is almost unusable behingd a flat port because of vignetting at wide angle settings.

I rate this lens highly for a mid range zoom and have been pleased with image quality. I can focus to within 1 cm of the front of the port. I can think of no other mid range zoom lens that can do this. This is really a lens for those that like the idea of a mid range zoom but are frustrated with poor close focus ability of Nikon and Canon alternatives. I bought it after a true macro lens and fisheye lens so I do not view it as a 'one lens fits all' bit of kit.

I came up with my own zoom gear built out of bits of plastic and rubber -i deas taken from the 'build your own focus gear' in the DIY forum. The zoom lock switch needs to be taken in to account.

Hope that helps

#4 Deep6

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Posted 14 August 2007 - 02:43 PM

Thanks pakman and tkr for your pompt and helpful replies.

I did the numbers on the Sigma 17-70 mm; the zoom extension is too long for partical use in ports.

tkr,

May I assume you are using a compact dome port ~ 6.5' to 6.7" diameter with the 40mm extenson?

I made a zoom gear from some Ikelite plastic gears for my Sigma 24 to 80 zoom. I like the ideas in the DIY form.

Now, what do I hock to get the Sigma lens????

Edited by Deep6, 14 August 2007 - 02:44 PM.

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