I'm not too sure of the science of it; you may be right in your numbers.
Thinking back, I'm sure some of the increased problem is due to not using a
hood. Normally I leave the Tiffen 41-43mm extension on all the time to
protect the lens, and it acts as sort of a hood. But adding the 81a puts the
first piece of glass out front again I suppose, so there was no hood
protecting it. I guess this would be a problem with an F30 and
glued/taped-on filter combo as well.
Wayne
----- Original Message -----
From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxx>
To: <olympus@xxxxxxxxxx>
Sent: Sunday, June 25, 2006 9:22 AM
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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