Thank you, Moose -- so, in a nutshell, if I'm careful enough to avoid
anything touching the front element (rely on the hood and cap) and I
learn to clean it safely, I'm probably better off using filters only
as needed? Is that your practice, BTW?
Phil
On Jan 05, 2008, at 20:31, Listar wrote:
> 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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