[LRflex] Re: Water Spots? My analysis (for what it is worth)
- From: "Aram Langhans" <leica_r8@xxxxxxxxxxx>
- To: leicareflex@xxxxxxxxxxxxx
- Date: Tue, 04 Oct 2005 12:02:24 -0700
Coming late to the party.
I would wager the "darkness" at f-22 is not a factor, but as you stop a lens
down, the cone of light gets narrower. The off-the-focal-plane dust would
appear darker, smaller as this cone narrows. It would still be translucent
as it is not on the sensor. The distance from the rear element to the
sensor, as well as the diameter of this element should play a role. Since
this element moves in most lenses as you changed your focal distance to the
subject, this would also alter the angle of this cone. I buy the dust on
the AA filter as the cause, and all the above mentioned factors as the
seeming inconsistency seen in the non-scientific tests done to date.
Since the image itself is virtually free, try the same f-stop but at
different focus distances from infinity to as close as it goes with each
lens. If you see spots, then use that focus distance and try different
f-stops to see if it gets worse or better. Manipulating too many variables
at the same time always leads to seemed inconsistencies.
Aram
>From: "JR Geoffrion" <jr@xxxxxxxxxxxxxxx>
>Reply-To: leicareflex@xxxxxxxxxxxxx
>To: <leicareflex@xxxxxxxxxxxxx>
>Subject: [LRflex] Water Spots?
>Date: Sun, 2 Oct 2005 17:54:25 -0500
>
>David,
>
>What you have are dust spots. Dust spots will be more visible as you stop
>down. The Telyt with the 2x is pretty dark which explains why you see the
>spots more.
>
>To see the spots, take a lens stop it down to f22 [at infinity] and shoot a
>uniform surface (I typically more the camera to make sure the surface is
>really "smooth"). Spots should be in [relatively] the same position
>everytime (it's dust -- and most will move around a little).
>
>Hope this helps.
>
>JR Geoffrion
>http://www.jrgeoffrion.com
>
>
>----- Original Message -----
>From: "David Young" <telyt@xxxxxxxxx>
>
>Whatever's causing it, might it be the angle of the light rays? Perhaps
>the 400 Telyt w/2X creates rays of a particular angle, compared to others?
>
>If it's dirt on the sensor, shouldn't it be the same in all photos?
>Most of my lenses don't show the problem at all!
>
>Bloody curious, it is!
>
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