Clear lense protector/filter

eqwalker

eqwalker

Active member
Recently I purchased a Tiffen 72mm filter kit and it included a clear lense that you can use as a protector. I tried it and noticed that in auto-focus it seem to always be a tad bit out of focus. But just barely. Has anyone noticed this before? Am I doing wrong in using it? I thought it would be a good idea to protect the main lense.
 
Re: Clear lense protector/filter

eqwalker, please clarify, are you saying that you cannot achieve sharp focus in auto focus, but could in manual focus---- or what? Protecting the front element of your lense is not a bad idea and in principle, a clear filter should not affect the lens differently that the others in terms of focus/sharpness(unless they are a diffusion/effects filter)-- did you try the other filters?

Bill Turner
Century Division
Schneider Optics
 
Re: Clear lense protector/filter

Yes, I was able to achieve a sharp focus in manual. But in auto is appeared to be just a little off. I did not try any of the other filters since this was an indoor shot and I didn't need any other filtering. Granted I am running in the F5 position which the focus is assisted. But my shots were fixed tripod shots with hardly, if any, movement from the stage that would have "outrun" the focus assist. The kit was their UV filter kit which included their outdoor UV and a warm indoor UV. It also included the clear protector lense. Without the clear lense screwed on everything looked and stayed fine. The focus assist kept everything sharp. I was wondering if the lense was confusing the focus assist in some form or fashion.
 
Re: Clear lense protector/filter

Why don't you just try the UV filter. I always have a UV filter on all of my lenses, unless I am using a different filter. If you have an indoor and outdoor UV filter you should be fine. I personally wouldn't use a clear filter, it just doesn't sound right.
 
Re: Clear lense protector/filter

Very interesting, a couple more questions:

Did this happen (or was it noticeable) at all focal lengths, wide to tele, or just at the long (45mm) end? If you focused manually and switch to auto, does the focus change? If there was a problem with the filter flatness one would normally expect the camera to refocus to compensate-- have you checked the focus number reading with and without the filter-- are they the same or different?

Also check with the other filters to see if the same thing happens.

I am trying to imagine a scenario where a reflection off the filter (is it anti reflection coated) could cause some issue, but without much success. The focal length of the zoom is so short (45mm) it is unlikely that the filter quality would be the issue, but one never knows.

Bill Turner
Century Division
Schneider Optics
 
Re: Clear lense protector/filter

Have you tried auto focus without the UV filter?
If you can achieve sharp focus without the Tiffen UV filter, then there must be something wrong with the filter.
 
Re: Clear lense protector/filter

Good questions Bill. I will try those different things and see what I come up with. Right now my DVX is at Panasonic getting the firewire port repaired under warranty (augh). It appears the firewire port never worked straight from the factory. As soon as I get it back (it has been 2 weeks now) I will gladly try your suggestions (and others on the post) and get back with my results. Thanks for all the replies.
 
Re: Clear lense protector/filter

Bill, I have a 72mm Schneider UV filter and needed more lens protection for these races I shoot. I use a Cinetatics Matteblox that uses those 4x4 filter holders that velcro into the mattebox. If I get a optical flat uv filter for the matteblox Will the larger distance between the lens and the filter affect anything aperture or focus wise?
 
Re: Clear lense protector/filter

Dear PFP_VIDEO

No, the distance the filter is in front of the lens should have no effect on focus or exposure. Clearly, if you move a filter too far away from the lens you will eventually get vignetting (at wide angle and close focus first) but with 4x4's and the DVX100 with out a wide angle attachment, you will have no problem.

One point that was mentioned on this forum in another thread is the possibility of imaging the reflection of the lettering on the front of the camera lens under certain conditions. painting out the white lettering on the lens mask with flat black paint is a good idea.

Bill Turner
Century Division
Schneider Optics
 
Re: Clear lense protector/filter

I think I have the same problem. The guy at a local store sold me a Clear Tiffen filter marked "Haze 1." I didn't thinnk too much about until you brought it up.
 
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