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06-24-2008, 07:21 PM   #1
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DA* 16-50 owners

Does your lens look like this?


06-24-2008, 10:14 PM   #2
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got a nice round iris here (only thing that looks like you may have meant when you asked about the "like this")
06-24-2008, 10:56 PM   #3
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QuoteOriginally posted by morfic Quote
got a nice round iris here (only thing that looks like you may have meant when you asked about the "like this")
Yeah, talking about the iris. This one is probably going back.
06-24-2008, 11:01 PM   #4
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Please take a photo with it before you send it back. I'd like to see what effect that has on the IQ

I'm sure that it's flawed, but you never know. It might just take the right shape when it's snapped on the camera

06-24-2008, 11:14 PM   #5
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Actually quite some of my lenses (current ones or sold ones) have similar non-circular iris shape when stop down like shown in OT, but I've never seen any IQ issue because of that.

If I were you, I'd do some simple test and make sure it focuses properly. Then bring it out and take some real world photos. If you are happy w/ the results, it's a keeper
06-24-2008, 11:30 PM   #6
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I have 2 16-50's in front of me and both of them do not have circular irises stopped all the way down like that. play with the aperture rod thing and see that the shape changes. It doesnt seem to effect image quality of either lens
06-24-2008, 11:44 PM   #7
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You might see it in out of focus highlights.
Plug in the old xmas tree, light it up, shoot someone at a distance in front of it and watch the shape of the lights in the OOF area. (And your wife thought having the xmas tree still in the room was a bad idea....)
06-25-2008, 01:39 AM   #8
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QuoteOriginally posted by morfic Quote
You might see it in out of focus highlights.
Plug in the old xmas tree, light it up, shoot someone at a distance in front of it and watch the shape of the lights in the OOF area. (And your wife thought having the xmas tree still in the room was a bad idea....)
Remember, stopped down all the way like that, there is hardly anything OOF. So I don't think it would be a problem or showstopper, unless you have this kind of iris with a macro lens, where high F values are often combined with (still) lots of OOF areas in pictures.

As other people suggested, swing the aperture through its' range and see if it changes to more circular shapes on lower F values. That's where it is going to matter.

06-25-2008, 03:12 AM   #9
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These were taken at 50mm, focus set at .3m (closest) and the light is about 35m away. The black stuff is from the dirty window I was shooting through. All images normalized to the f/2.8 image.

f/2.8:

f/4.0:

f/5.6:

f/8.0:

f/22:

What do you guys think? I'm seeing that the "circle" is smoother/rounder at the top at f/4 (and slightly at 5.6 and 8). Acceptable or is this lens capable of being better?

Last edited by GoSharks; 06-25-2008 at 03:38 AM.
06-25-2008, 12:13 PM   #10
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I had a quick look on my DA*16-50. Looks very similar to GoShark´s latest pictures. Stopped down all the way the iris is slightly elliptical, albeit only marginally. I guess this is OK.
However, the iris appears a lot rounder than the one in GoShark´s first picture. His latest pictures - icluding the one at f 22 - look better than the first one.Could this be due to the lens not being alligned to the camera?
06-25-2008, 12:37 PM   #11
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QuoteOriginally posted by PePe Quote
I had a quick look on my DA*16-50. Looks very similar to GoShark´s latest pictures. Stopped down all the way the iris is slightly elliptical, albeit only marginally. I guess this is OK.
However, the iris appears a lot rounder than the one in GoShark´s first picture. His latest pictures - icluding the one at f 22 - look better than the first one.Could this be due to the lens not being alligned to the camera?
I should clarify that the second set of pictures are of the OOF blur from actual images taken with the lens and not of the iris itself.
06-25-2008, 12:47 PM   #12
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QuoteOriginally posted by GoSharks Quote
I should clarify that the second set of pictures are of the OOF blur from actual images taken with the lens and not of the iris itself.
If so I won't really worry about it, unless you really want to go through the trouble of sending back and stuff.
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