Do high-quality filters cause flare?

This topic comes up frequently, most recently in a thread I was involved in over in another forum. So I set up a brief test this morning.


I used my 5DII and two different lenses (24-105mm f/4<span style="color: #ff0000;"]L IS @ 24mm and70-200mm f/2.8<span style="color: #ff0000;"]L IS II @ 200mm), each shot wide open and at f/11 without and with a B+W MRC UV filter. The appropraite lens hood was used. The light source was a halogen lamp (150W equivalent) in the upper left corner of the frame, in an otherwise completely dark room (literally, in fact, a darkroom).


This is rather a worst-case scenario - a small, very bright light source right in the corner of the frame, a pitch-black background, and no extraneous features in the image to mask the flare.


24-105mm f/4<span style="color: #ff0000;"]LIS @ 24mm:


[url="http://www.flickr.com/photos/dr_brain/5600755377/lightbox/]http://farm6.static.flickr.com/5106/...2f5d485c_b.jpg[/url]





70-200mm f/2.8<span style="color: #ff0000;"]LIS II @ 200mm:


http://farm6.static.flickr.com/5141/...229e01ed_b.jpg





With both lenses in this rather extreme example, there is a very slight reduction in contrast with the filter installed. It's a little more noticeable at 24mm, probably because of the very tangential angle at which the light is positioned relative to the optical axis of the lens. That's unfortunate, since wide angle lenses are more likely to include a bright light source (i.e. the sun), and from a protection standpoint a filter is more important on a wide angle lens, because the lens hoods are much shallower and offer less protection.


Personally, it's not enough of an effect for me to eschew the easier cleaning, weather-sealing, and protection that a high-quality filter provides.


Thanks for looking!


--John

Nice demo Jon, and thanks for taking the time to share this!


The images without the filter certainly look more pleasing to me as well.


I think the improved contrast may make it appear that the bare lens has more flare, but I think it just makes it more obvious, because those shots are clearer.


I agree that the weather sealing and element protection appear to worth the tradeoff.


I think that I will now consider to remove the filter on occasion, if I have a special shot.


Rich

Quote:

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Originally Posted by Richard Lane

I think the improved contrast may make it appear that the bare lens has more flare, but I think it just makes it more obvious, because those shots are clearer.

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That's my interpretation as well. Interestingly, when I took the shots and checked them on the rear LCD, I though it was odd that the with-filter shots looked like they had less flare - so odd that I shot another set, just to be sure. But of course, that's why you use the histogram for on-camera review - the camera's LCD is not a fully adequate representation of the image, and upon review on my computer, the slightly reduced contrast with the filter was evident.


It occurs to me that there's a way to quantify this - a lightbox in the frame with a transmission step wedge (anyone else remember those from printing negatives - real ones, not RAW files?) would allow one to measure the loss of contrast with the increase in flare.

Yes.., so the bare lens has improved flare control, but because the contrast is greater some of the flare rings stand out more, however.., the filtered lens does in fact have more flare as well as some additional secondary flare spots.


In addition, the filtered lens also has more flare (and blown-out highlights) as you get closer to the light source, especially directly in the upper left portion of the frame.


Rich

Quote:

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Originally Posted by neuroanatomist

Personally, it's not enough of an effect for me to eschew the easier cleaning, weather-sealing, and protection that a high-quality filter provides.

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John


Good comparison


I wonder what other factors such as sharpness, color etc... that you loose using the filter.


I have always known there is some loss when you add the filter, and thats why we pay top dollar for the best filters we can find to protect our lenses.