Philippe Dambournet wrote:
> <snip>
>
> Thanks for the filter tip. Anything good enough not to degrade the
> performance of the 14-54 is perfect.
Philippe Dambournet wrote:
> <snip>
>
> I guess B&Ws are the filters that do not degrade optical performance... ouch.
>
You appear to be operating under a misunderstanding. All filters degrade
the image. Most will not do so to an extent that you will notice, but
the simple act of passing the light through two parallel, flat,
air/glass surfaces has an optical effect, separate from the issue of
coatings. You are in effect adding an unnecessary element to the lens so
much time and effort was spent in designing.
If you find it necessary to have a filter on the lens, there is no
excuse with digital to avoid taking identical shots with and without the
filter at a few different focal lengths and apertures and checking them
carefully against each other. Some filters have defects that may
seriously degrade image quality but are not noticeable to the eye.
According to Gary Reese's tests, this can happen even with the top brands.
A few years ago, we had a fellow on the list who whined on and on about
the poor image quality of one of his Zuiko lenses. We proposed all sorts
of possibilities until one day the light dawned and I suggested if he
had a filter on it (which he had never mentioned) that he should remove
it. Problem solved.
With digital, the plot thickens. The front surfaces of sensors and the
filters in front of them are very flat and shiny, much more so than
film. This occasionally causes problems with lenses designed for film
with element surfaces that are relatively flat. Lenses designed for
digital try to avoid that and use even stronger AR coatings than before.
However, a filter has two perfectly flat surfaces, and even with those
specially coated for digital, there are occasional odd effects in night
shots. I've seen a few examples where weird looking things in images
turn out to be a result of using filters.
So sure, if you are clumsy or paranoid, use a filter. But test it when
you get it and be aware it can cause odd image effects.
Moose
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