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Vivitar S1 70-210 + Polarising filter = weird problem
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PostPosted: Sun Apr 05, 2015 8:07 pm    Post subject: Vivitar S1 70-210 + Polarising filter = weird problem Reply with quote

Hello,

First of all, if it isn't the best place for this topic I would ask moderators to move it.

Today I've noticed weird thing when using Vivitar Series 1 70-210 (Kiron ver) with Circular Polarising filter on my Olympus OM2-SP. At 210mm I was focusing without polarising filter at a tree about 150-200m away and lens was focused a bit (2-4mm move of the barrel) before hitting infinity stop. However, when I've put polarising filter on it then I need to turn lens to infinity stop to get the same tree in focus.

Of course I didn't move in that time. It was the first time I've noticed such thing. What's more I cannot get far away objects in focus when filter was on the lens and of course it wasn't a problem when lens was without filter attached.

Did any of you had similar problem? I've only noticed it on this telephoto lens. I took a few photos, but I need to wait until film will be developed to see if there's a problem with focusing. I come back home after sunset so I will test it with digital body tomorrow morning.

Oh, by the way filter is circular polarising filter, maybe not the most expensive, but not the cheapest either and it does pretty good job without making mess of the photo or producing a lot of reflections (like the other one I got - a cheap 'free' add-on when I was buying the lens).

Hope to hear your thoughts about that.


PostPosted: Sun Apr 05, 2015 9:04 pm    Post subject: Reply with quote

Hello,

I've tested the problem on digital body despite night time (there are some bright street lamps far away, so perfect for the test).

On Viv 70-210 at 210 I couldn't reach infinity with this filter.
It's weirds as on other lenses there's no such problems, although next telephoto I have is 150mm and I'm curious if the problem is just this filter and this lens or this filter and telephoto lenses.

I would appreciate any comments if you had encounter similar problems or maybe have used this particular lens with some particular polarising filter with success.


PostPosted: Sun Apr 05, 2015 9:09 pm    Post subject: Reply with quote

I've got the SI 70-210 2.8 / 4 Komine with Canon FD mount, and a circular pola', I'll try it tomorrow on a Canon AE1 and the Sony.


PostPosted: Mon Apr 06, 2015 5:37 am    Post subject: Reply with quote

I have heard the using CPL will alter the focus point at different focal point in a parfocal zooms especially if it is a tele zoom.


PostPosted: Mon Apr 06, 2015 8:18 am    Post subject: Reply with quote

I understand there are two layers of glass and a layer of polarising material in a CPL filter. The combination of which will cause some refraction making adjustment of focus necessary.


PostPosted: Mon Apr 06, 2015 10:48 am    Post subject: Reply with quote

Interesting. Thanks for sharing Smile.


PostPosted: Mon Apr 06, 2015 1:09 pm    Post subject: Reply with quote

Hi guys, thank you for replies. It's quite interesting thing and since night is gone I made a few tests.

I have 2 CPL filters - one complete cheapo that was added for free to a lens - 67mm and second also cheap, but not the cheapest - 77mm.

On Vivitar S1 70-210mm: 67mm version doesn't alter focus, 77mm alter focus significantly and at 210mm I cannot focus at infinity.

On Vivitar S1 28-90mm: 67mm version doesn't alter focus, 77mm alter focus but very slightly and at 90mm I'm still able to focus at infinity

On Vivitar S1 24-48mm: 77mm alter focus, but in other way - at 24mm I reach infinity focus when barrel is set a bit after 20m mark, at 48mm infinity focus is at infinity stop. Without filter at both ends lens focuses slightly beyond infinity, but very slightly.

Both filters aren't the best, that's for sure, but they don't degrade quality that much (only slightly, when pixel peepping) and work great as a polarisers. Of course I could buy more expensive CPL filter, but I'm very curious if that's going to change anything. What do you think?

I'm using 77mm size as a most universal size to use on 62-77mm filter size lenses with step up ring if needed. I thought about buying Marumi DHG or DHG super CPL (as it seems quality/price ratio is quite reasonable), but still I'm not sure if that's going to improve anything.


PostPosted: Mon Apr 06, 2015 5:01 pm    Post subject: Reply with quote

I generally only buy the B+W filters.

get what you pay for in filters.. in my opinion.

http://www.bhphotovideo.com/bnh/controller/home?O=&sku=10889&gclid=CIi6heyT4sQCFQaPaQod8JcAHw&Q=&is=REG&A=details


PostPosted: Mon Apr 06, 2015 7:05 pm    Post subject: Reply with quote

vroger wrote:
I generally only buy the B+W filters.

get what you pay for in filters.. in my opinion.

http://www.bhphotovideo.com/bnh/controller/home?O=&sku=10889&gclid=CIi6heyT4sQCFQaPaQod8JcAHw&Q=&is=REG&A=details


I partly agree, it's reasonable if you put something in front of nice lens that it would be something of decent quality, however in my opinion B+W filters are simply too expensive as a brand. They probably are good, but I'm sure there are other brands that cost less and are of similar quality.
By the way, did you tried that B+W filter you recommend with telephoto lens?

I seriously wonder if it's just problem of cheap filter or something in common for all.


PostPosted: Mon Apr 06, 2015 7:35 pm    Post subject: Reply with quote

It's not the filter, or the quality of the filter. I'm sure It's the lens.
Last night I remembered taking this Komine Vivitar SI 70-210 2.8 / 4 with me when I went to Canada last year and I took a load of pictures of the fall colours around the lakes close to my brothers house, and about half of them were blurred. Thinking back, about half way through the walk I thought I'd try the Hoya circular polarizer, and I think that's where the pictures turned blurred, what other reason was there for a sudden change?
Today I went out with the same lens and the Hoya polarizer, and every picture with the filter was blurred, badly blurred - beyond a bit of camera shake. I used a monopod and got decent shots without the filter. The strange thing was, the Sony focus peaking looked exactly the same with and without the filter, but magnifying the live view it was obvious the image was blurred. It's very odd, but the pictures tell the tale. I have PP'd the clock tower picture a bit, I shot RAW, and f4, and wanted to see what the standard Photoshop conversion looked like. The gravestone shots, wide open at 2.8, are untouched (except for sizing) and the monopod was jammed against a bench and as good as a tripod.
The clock is effectively infinity at 250 meters, the gravestone is about 15 meters away.









For some strange reason this lens will not focus properly through a polarizer, I probably took 50 pictures to try it and none with the filter had any sharpness at all.


PostPosted: Mon Apr 06, 2015 7:48 pm    Post subject: Reply with quote

PhantomLord wrote:
vroger wrote:
I generally only buy the B+W filters.

get what you pay for in filters.. in my opinion.

http://www.bhphotovideo.com/bnh/controller/home?O=&sku=10889&gclid=CIi6heyT4sQCFQaPaQod8JcAHw&Q=&is=REG&A=details


I partly agree, it's reasonable if you put something in front of nice lens that it would be something of decent quality, however in my opinion B+W filters are simply too expensive as a brand. They probably are good, but I'm sure there are other brands that cost less and are of similar quality.
By the way, did you tried that B+W filter you recommend with telephoto lens?

I seriously wonder if it's just problem of cheap filter or something in common for all.



I have those B+W filters on all my canon EF lenses. And yes, I normally go without a filter for cheaper older lens.
I have one on my 100-300L.

Roger


PostPosted: Mon Apr 06, 2015 8:14 pm    Post subject: Reply with quote

I use this Hoya polarizer on other lenses and have no problem with it at all. I have a 67 and a 72 pola and some step rings which I'll try on the Vivitar. And I'll try some screw on ND filters.


PostPosted: Mon Apr 06, 2015 8:39 pm    Post subject: Reply with quote

Thank you Lloydy, I appreciate that you took time to do a test. The result's are exactly the same for me so it's probably something in the lens design. Nevertheless this photos shoot wide open without the filter are very good quality and that made me thinking if my, older copy is that good as well, since I very rarely shoot it wide open.

I must try this filter on some other telephoto lenses, but that may took time since I need to borrow some from a friend Wink.


PostPosted: Mon Apr 06, 2015 9:05 pm    Post subject: Reply with quote

PhantomLord wrote:
Thank you Lloydy, I appreciate that you took time to do a test. The result's are exactly the same for me so it's probably something in the lens design. Nevertheless this photos shoot wide open without the filter are very good quality and that made me thinking if my, older copy is that good as well, since I very rarely shoot it wide open.

I must try this filter on some other telephoto lenses, but that may took time since I need to borrow some from a friend Wink.


Perhaps you can go to a photography shop and try a filter on it...?


PostPosted: Mon Apr 06, 2015 9:39 pm    Post subject: Reply with quote

I've got a bunch of lenses using 62mm filter so I'll try some primes and other zooms with the Hoya filter. It's intriguing me what's going on. Question


PostPosted: Tue Apr 07, 2015 5:38 am    Post subject: Reply with quote

With longer focal lengths and somewhat fast lenses the quality of the front filters are not always good enough.

Filter glass is flat - at the first examination. But with proper instruments like an optical flat and an old sodium vapour safelight one could see rings / structures. These show how flat a glass surface is. On can count the interference rings, and with this one can get the filter form differences in wavelenghts (lambda) of the light used.

For astronomy with their long focal lengths filter often need to have a flattness of 1/10 or even 1/20 off the measured wavelength.
For machine vision a friend of mine wrote this article with her collegue:
http://www.vision-systems.com/articles/print/volume-16/issue-10/features/filters-factor-into-optical-imaging.html
There they recommed filters with ~1 wavelenght form accuracy - about 500nm.

Cheap photographic filters could even show thickness differences about 50000nm = 50m = 0.05mm.

Canon EF 100-400 users somtimes think their lens is crap, until they learn to do a test without filter - then they see full sharpness Smile
Some of the form problems can be spherical - so the filter acts like a lens with very long focal length. This can change the focus setting.
Some filter form problems can be seen in bad bokeh, for example with those fast 70-200mm/2.8 zooms this is sometimes seen.

I have asked many photo filter manufacturers on the Photokina about form tolerances. they dont tell you about this. Hoya had a setup to show this difference, but most visitors didnt take notice.
It is much easier to work on good transmission, to test transmission and to understand transmission. So this is the main marketing concern at the moment.


PostPosted: Tue Apr 07, 2015 12:02 pm    Post subject: Reply with quote

I have to eat my words here......it is the pola' filter. I've tried it on a different Vivitar 90-230 / 4.5 zoom, a Chinon 200 / 3.5 and a Tamron 300 / 5.6 and the filter is rubbish on all of them. All the lenses were fine with a ND4 filter.
I'm sure I have used this Hoya pola' in the past and it was OK, and the filter looks OK and has no damage. But whatever....it's no good now.

I am about to try some other large pola's on different lenses to see what results I get.


PostPosted: Tue Apr 07, 2015 12:26 pm    Post subject: Reply with quote

Well I think ZoneV explained pretty nice what's going on and I understand that on tele lenses those imperfections just have increased impact on the lens. Now I need to look and save some money for better CPL filter.

Do any of you could recommend particular CPL? I know there are plenty of great filters but since I don't have big bag of money to spend on it I would be aiming for something decent in the range of 35-50 and I'm sure that not everything is totally cr..p with price tag under 100, so please stay reasonable Wink.


PostPosted: Tue Apr 07, 2015 12:39 pm    Post subject: Reply with quote

There is an old test on lenstip.
http://www.lenstip.com/115.1-article-Polarizing_filters_test_Introduction.html


PostPosted: Tue Apr 07, 2015 7:26 pm    Post subject: Reply with quote

I used a Hama 87mm circular pola' on a Vivitar Series 1. 28-90 / 2.8 3.5 zoom and I can't see any difference in sharpness with or without the filter.


PostPosted: Tue Apr 07, 2015 8:09 pm    Post subject: Reply with quote

Lloyd, do you by any chance wear polarizing glasses?


PostPosted: Tue Apr 07, 2015 9:25 pm    Post subject: Reply with quote

I wear photochromic glasses, I don't think that would make the difference in the picture being as seriously blurred as the filter makes it.

These are with a Chinon 200 3.5, shot wide open on a solid tripod with the focus taped so it wouldn't move.






the level of blurriness, and the type, are strange. It's nothing like motion blur and very much like a loose or damaged lens element. but the lens is OK with a ND filter or a UV. The pola' filter looks perfect, just the same as the the other pola, but it obviously isn't.


PostPosted: Wed Apr 08, 2015 12:31 am    Post subject: Reply with quote

I can think of one more factor that would lead to the lack of sharpness in this case. When it comes to polarizing filters, one tends to tighten them well so that, when the front element is being rotated, the whole thing won't unscrew. I remember reading an article (can't find it right now) stating that the filter glass tends to bend when the filter is being tightened in place. If I remember correctly, the conclusion was to leave the filter loose in thread or not to use it at all.

I guess it will very much depend on the filter's quality but this theory does make sense to me since you would end up with a concave/convex glass element in front of the lens. That would only add up to everything ZoneV wrote about.

BTW, I wonder if the tension coming from a tightened filter could also affect at least the front element of the lens? Not by bending it of course, but if the lens isn't in its best shape or has been ineptly tinkered with, I guess that there could be enough force to displace whatever is loose inside the barrel. But that's just my uneducated guess Smile


PostPosted: Wed Apr 08, 2015 7:22 pm    Post subject: Reply with quote

Found it! Here is the article I had in mind:

http://www.clarkvision.com/articles/evaluating_filter_quality/

It covers much more then I remembered, among others it explains in simple words why filter quality is far more important at longer focal lengths and suggest a few simple tests to determine if your filter is any good. Great read.

And here's a fun and informative comparison of the difference between poor and good quality filters. Not very scientific, but (especially) the last photo gives you something to think about:

http://www.lensrentals.com/blog/2011/06/good-times-with-bad-filters


PostPosted: Wed Apr 08, 2015 9:07 pm    Post subject: Reply with quote

Two interesting articles, I've seen the Lens Rental one before but it's still a good read.

I took the glass out of the Hoya ( it's branded Jessops but the leaflet in the box was Hoya ) pola' filter and measured the thickness at various points on the glass, and discovered 0.0015" difference in the thickness, side to side, over the 2.325" diameter glass. It was also thinner in the centre than around the rim by a similar amount.

The design of a pola' filter doesn't generally make it prone to stressing either the filter or the lens when screwed on, the glass part of the filter rotates freely on the part screwed into the lens, in the case of this particular filter the rotation has more play than the other pola's I have. The 67mm pola' that works perfectly has no play in the rotation at all.

I think that this filter is a cheap and nasty item that is sold as a store brand, and you get what you pay for. I also think the problem is mainly the dimensional accuracy of the glass thickness. One and a half thousandths of an inch over two and a quarter inches doesn't sound like much, one of my few remaining hairs is two and half thou'. It might be an acceptable tolerance for other filters, but probably not for polarizers.

EDIT....
It's just dawned on me, putting the glass back in this filter, that this filter is a LINEAR polarizer and not a CIRCULAR polarizer, which the other pola, the one that works, is. Embarassed
So.....my comments here might just apply to linear filters ? But my understanding is, the difference affects exposure / metering on modern cameras, as well as auto focus, which is why circular are the most used now. Using a linear with a manual focus lens and manual metering should not affect focus in the way this filter has.