The article refers to using filters on digital. Rightly or wrongly, I have
always used either UV or Skylight filters on my lenses for film. When I was
"retiring" my 28/3.5 I was surprised to see all the small scratches on the
filter, while the lens element itself was pristine. Now, I pretty much always
used the metal hood with this lens. The hood is largely unmarked also, so a
hood may not be everything.
Also on the filter issue, there was an interesting thread on the 4/3 forum
concerning a test of a Tamron 300/2.8 and the (beneficial) effect on the lens'
performance wide open with the big Tamron filter mounted. The thread discusses
why this may happen, and why it appears to most noticeable with large
apertures. Now, I'm no expert, but the thread seemed reasonable to me. Any
other views? The thread is:
http://www.fourthirdsphoto.com/vbb/showthread.php?t=643
Martin
-----Original Message-----
From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx]
Sent: June 25, 2006 8:23
To: olympus@xxxxxxxxxx
Subject: [OM] Re: Protective Filters
I hear you and I don't use "protective" filters myself; gave that up
long ago for decent lens hoods. However, something doesn't seem to
compute. I would assume (I know, assumptions are dangerous) that
1) multicoated surfaces pass 99.5% of the light and reflect only 0.5%
2) the low pass filter on the sensor is multicoated
3) the backside of the UV or other filter is multicoated
If all three are true then only 0.5% can be reflected back to the front
filter, 5-15% of that will be lost getting back to the front of the
lens, and 99.5% of that will pass out through the filter and only 0.5%
of that will get reflected back to the sensor and 5-15% of that will be
lost again trying to pass back through the lens. Seems to leave only a
teeny-tiny amount of light to cause any mischief.
So what's wrong with this analysis? I'm sure that assumption #1 is
pretty close to correct. If anything it may be 0.1% reflectivity rather
than 0.5%. Are #2 and #3 simply bad assumptions?
Chuck Norcutt
Wayne Culberson wrote:
>
>
>
>>The very best demolishing of the protective filter myth even not
>>taking into account the tests at Gary Reese's site.
>>
>>http://forums.dpreview.com/forums/read.asp?forum=1021&message=18960184
>>
>>
>>
>>Winsor
>>Long Beach, California, USA
>>
>
>
> Perhaps that explains why I had so many low contrast/flare pictures with the
> C5050 on the last trip to Bolivia. It was the first time I'd used a filter
> on the digital down there, an 81a of course. So it looks like there is no
> winning with a digital camera at high altitudes.
> Wayne
>
>
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