Be careful with those filters !

luisalegria · Expire: 2018-01-18

While testing my new Sears 200mm, I was getting dismayed by the apparently poor quality of its rendering; it seemed the thing was just not focusing properly, or it was hopelessly fuzzy wide-open.

But I thought to try it without hood or filter, and suddenly it became a decent lens. The problem was the old 67mm UV filter. It was either fooling the focus confirm on the K100D or it was just badly degrading the image. I've never noticed such a thing before.

With filter, 100% crop, f/3.5, infinity focus -

Without filter -

This filter was formerly on a Tokina 28-80 zoom that I had dismissed as a lousy lens after trying it out. Maybe that one isn't so bad either.

F16SUNSHINE · Expire: 2011-11-18

Iteresting Your samples show a very dramatic effect. How did the scene look thru the viewfinder? I have not experienced such bad degradation of IQ from a filter before.

Attila · Expire: 2025-11-18

I use filters as lens cap only in storage.. Most of filter degrade image quality, Orio suggested to use B+W filters what are not degrade image quality.

luisalegria · Expire: 2018-01-18

I was very surprised too.

The image looked good through the viewfinder, but frankly I can't really focus precisely just by viewing the image, as the K100D standard focusing screen is optimized for brightness and doesn't have a proper groundglass. So I have to depend on the focus confirm.

I am coming to the conclusion that I should replace the focusing screen with a groundglass/split-image one.

Attila · Expire: 2025-11-18

with split focusing screen I need always calibrate light meter, not so convince. For example at f4 I have to add +1.0 at f5.6 +1.7 etc, At every aperture changes I have to change light meter set too.

luisalegria · Expire: 2018-01-18

Good point. I will have to research more.

For what camera did you change the focusing screen ?

Attila · Expire: 2025-11-18

Olympus E-1 + Katz-Eye split screen (one of the most expensive and best ones)

LucisPictor · Expire: 2013-12-03

I have never seen such a strong influence of the filters I use.
But I try to use only very good ones (B&W, Hoya etc.).

Attila · Expire: 2025-11-18

Is Hoya close to B&W ?

bob955i · Joined: 15 Apr 2007 Posts: 2495

B+W are easier to clean than Hoya due to the different coating.

As an aside, if you use Tokina lenses, the glass is supplied by Hoya, who happen to own Tokina....

Farside · Expire: 2013-12-27

I'm surprised at that. First time I've seen such a bad effect from a filter - what make was it, so we know to avoid them?

ChrisLilley · Joined: 01 Jan 2008 Posts: 1767 Location: Nice, France

This might be a silly question, but ...
if you take some lens cleaning solution (isopropyl alchohol) and a lint free cloth, and clean both sides of the filter, does that clear up any of this blurring distortion?

Is it a coated or uincoated filter?

If you hold the filter up to the light, is there a visible change in colour or any visible distortion or marks on the filter?

It seems like a really pronounced degradation. I have seen veiling flare from poor filters, but nothing this bad. (I only use B+W filters, now)

F16SUNSHINE · Expire: 2011-11-18

Hey BTW: The unfiltered shot looks pretty good for a wide open crop from a Sears lens. Wink

luisalegria · Expire: 2018-01-18

The filter is a plastic-rim Kalimar, from the 1980's I guess. It came with a batch of used equipment from that era and has been sitting in a box in our garage for a couple of decades.

I think it was pretty much the cheapest lens one could buy when it was new.

It is clean, more or less. No oil, no smears, a bit of coating loss and some little scratches, no more than most of my other (generally lousy) filters. The rim (plastic) is chipped, but not the glass.

It may be off-center, I can't easily tell, that may be the problem.

That POS is now safely in the trash.

The real problem may be that it was making the focus-confirm malfunction.

luisalegria · Expire: 2018-01-18

That Sears ain't bad - wide-open on that long shot it beats my Sigma AND Komura 200's, as well as the Meyer, Piesker and Soligor 180's. I need to take it out where there are real pictures.

LucisPictor · Expire: 2013-12-03

Laurence · Expire: 2016-06-19

Unless I forget Shocked

I generally take my filters off when I'm shooting. They are certainly useful as lens caps, and I think they would actually absorb a shattering blow by acting as a "sacrifice" for the lens. I have heard of shattering blows with a lens cap on where the lens cap does not break, but the lens does...of course that's only circumstantial, but it's so easy to use the glass filter for a lens cap anyway.

LucisPictor · Expire: 2013-12-03