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Archive 2012 · Dust in a Contax 85mm F1.4, is it hard to remove?
  
 
Bifurcator
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p.2 #1 · p.2 #1 · Dust in a Contax 85mm F1.4, is it hard to remove?


MRosth wrote:
Heres how it looked like

http://farm9.staticflickr.com/8209/8186957629_4c8d5a70d3_b.jpg
Before

http://farm9.staticflickr.com/8347/8188150321_c07de71af8_b.jpg
After - Same background and shoot at F16.


There are still some small dirt/dust dots but not as big as seen on the first picture


If you were to ask me I'd say that was all sensor dust. And the big black one was a massive spec that fell off between photographs. Even the rear element junk that Demitri is talking about isn't that defined. The Contax 85mm F1.4 doesn't have a rear element close enough to the sensor to make a spec that defined like that. Although I suppose it could be a spec attached to a fibre that was hanging out near the sensor. Who knows...

Anyway it's gone now so that's good. You still need to clean that sensor tho!




Nov 15, 2012 at 11:17 PM
thrice
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p.2 #2 · p.2 #2 · Dust in a Contax 85mm F1.4, is it hard to remove?


I agree with all other posters, this was debris on your sensor.


Nov 16, 2012 at 04:08 AM
MRosth
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p.2 #3 · p.2 #3 · Dust in a Contax 85mm F1.4, is it hard to remove?



DSC06315 by MRosth, on Flickr

This is shoot with SLR Magic Hyperprime at F16 with same camera NEX 7
No dust or dirt



Nov 16, 2012 at 10:48 AM
d.o.k
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p.2 #4 · p.2 #4 · Dust in a Contax 85mm F1.4, is it hard to remove?


thrice wrote:
Mmhmm, show me the lens and the sample shot. The laws of optics simply don't support the idea of individual dust particles inside or on a lens surface showing up in the image.

Well I don't own the lens anymore, precisely because it was a vacuum cleaner ! It's the Canon EF 17-55 f/2.8. I managed once the remove the front glass to blow the dust that was inside (btw there are tutorials for this particular lens, they're easy to find). But I sweated like a pig when doing it (screws are so close to the glass) so I prefered to sell it afterwards.
It had one or two big dust particles (let's say about 0.5mm) and it definitely showed on the photographs !



Nov 16, 2012 at 12:40 PM
 

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thrice
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p.2 #5 · p.2 #5 · Dust in a Contax 85mm F1.4, is it hard to remove?


Still don't believe you at all, I'm sorry.
Spend one week taking optical design classes at your local college and you'll realise how ridiculous this sounds.

Don't believe me? Take a black whiteboard marker and draw some 1mm dots anywhere on your lens (don't worry, whiteboard marker comes off) take some tripod-bound shots before and after of a white wall and tell me what you see.



Nov 16, 2012 at 02:42 PM
dimitris77
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p.2 #6 · p.2 #6 · Dust in a Contax 85mm F1.4, is it hard to remove?


That looks like sensor dust. Also what are you doing shooting an f1.4 lens at f16?


Nov 16, 2012 at 03:10 PM
simonw
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p.2 #7 · p.2 #7 · Dust in a Contax 85mm F1.4, is it hard to remove?


I think that being an alt lens a very simple test would be to take two pictures, one normal and one where you release the lens in its adapter and rotate it slightly. if the spots move then they are in the lens, if they don't then they are on the sensor.

Cheers, Simon W.



Nov 16, 2012 at 03:50 PM
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p.2 #8 · p.2 #8 · Dust in a Contax 85mm F1.4, is it hard to remove?


thrice wrote:
Still don't believe you at all, I'm sorry.
Spend one week taking optical design classes at your local college and you'll realise how ridiculous this sounds.

Don't believe me? Take a black whiteboard marker and draw some 1mm dots anywhere on your lens (don't worry, whiteboard marker comes off) take some tripod-bound shots before and after of a white wall and tell me what you see.



I agree with you 1000%, there's just no way (other than in bokeh highlights or maybe a macro lens on a tube) but I would not suggest he use WB marker. Grease pencil is safer.




Nov 16, 2012 at 06:59 PM
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