Filtrs; part 2

[abzphotoz]

There was a very interesting topic posted by Alex Gregory about the need for filters mainly for protection. I thought-

"why not just keep the lens cap handy and pop it on when you're not using it"...it only takes a second to take it off.

Instead of posting a reply I wanted to bring up a related question/topic; Polarizers for landscapes. I love the effect

they give you but now i'm really starting to wonder if the IQ is affected when using a good (B+W) polarizer with my 17-

40L. If I want to make a fairly large print, would the quality/sharpness make a significant difference?

[lester_wareham]

I can say I have checked good quality UV/protective filters in detail and these have negligible effect on image quality.

 

In terms of sharpness and AF operation there was no measurable effect using SRF software (see http://www.zen20934.zen.co.uk/photography/LensTests/Filter_AF/index.htm).

 

In terms of flare and ghosting in most cases issues were only seen under very harsh lighting differences equivalent to having the sun in frame and exposing for the land, even then the lens was often the limiting factor. There were one or two exceptions however, the 50/1.4 reacted strongly to a filter being fitted (see http://www.zen20934.zen.co.uk/photography/LensTests/Flare/index.htm)

 

A polarizer of course includes two glass layers and the polarisation film and so is likely to be more prone to flare. I can't say I have tested this. The flare tests are easy to do so I suggest you do your own tests and find out.

[manuel barrera houston,]

other then keeping a quality uv filter on my lens, I found that polarizers effects can be duplicated easily in photoshop, however, the need for neutral density filters is still there.

[zml]

What are you after, a good image or good image quality..? If the former, use whatever tools help you bring your vison to the finished photograph. If the latter then, ehem, start testing filters :-))) <br>

And to answer your question, in terms of sharpness and resolution you'd be hard pressed to distinguish a print of a picture made with and without a good quality filter. B+W polarizers are very good, BTW.<br><br>And addressing the "all in photoshop" stance, it is extremly time-consuming and difficult - nearly impossible - to replicate some effect of polarizers in post processing. For instance, try nuking reflections on non-metallic surfaces (that includes water, vegetation, etc.) in photoshop. Good luck with that!

[peter_foiles2]

Manuel-

 

"I found that polarizers effects can be duplicated easily in photoshop"

 

Really? How do you easily remove reflections in Photoshop? I am sure everyone would like to know-

[images_in_light_north_west]

"I found that polarizers effects can be duplicated easily in photoshop, however" would like to know that trick............

[manuel barrera houston,]

I was thinking of the dark blues, I normally do not shoot through glass, and if close enough can focus through it. I tend to like reflections as they add to the natural beauty, I guess that is why I am short and fat and some people are tall and slim. I did not say, I did not use polarizers but not as much as I used to. A long long time ago when I used film, I always used polarizers, very seldom now. I normally do have an nd filter with me. If you want to increase blues in certain areas only,that is very easy to do in photoshop. To remove reflections, a little harder, and even a polarizer will not remove all reflections. I find that placing my camera in an angle where the reflection can be avoided works much better, most of the time if it can be done.

[g dan mitchell]

<p>My general take of filters for "protection" is posted <a href="http://www.gdanmitchell.com/2007/12/27/uv-filter-or-

not/">here</a>. Summary: It isn't cost effective to use filters for protection and there are some image quality risks - and the UV

filtering effect of UV filters is wasted on DSLRs, which are not sensitive to UV the way that film was.

 

<p>A polarizing filter can be used for a variety of effects, most of which <i>cannot be duplicated in Photoshop</i>:

 

<ul>

<li>Control reflections from many sources: water, leaf surfaces, etc.

<li>Increase contrast in some situations, such as between clouds and sky.

<li>Reduce transmitted light, permitting use of a slower shutter speed and/or larger aperture.

</ul>

 

<p>I would not use a polarizer all the time. I would only put it on the lens when you need the particular effects it is there for.

 

<p>No filter can possibly be neutral in terms of image quality. (If filters were neutral then you could put 20 of them, or 100 of

them, or 1000 of them on your lens with no image degradation...) The question is whether the effect the filter produces is more

important than any image degradation (often minor, though it depends on the situation) that it might produce.

 

<p>Dan