UV Filters - reducing sharpness?

[Gerry]

Recently I became very concerned about the lack of sharpness that I was getting from my Rebel combined with my Canon 70-200 f2.8L IS. It was very soft. I explored why this may be happening via google and found this site that, along with the usual suspects, found that his/her UV filter was causing a significant amount of the problem. http://www.publish.com/c/a/Photo/How...r-Digital-SLR/ I did extensive test shots and discovered that my filter did in fact seem to cause slight but perceptible softness along with highlight reduction. I must admit that after cleaning it, it was not quite as bad! However, it was enough to cause me to consider leaving my filter off in future. It was used primarily as protection. I don't think this is a very smart move, though. I suspect the filter I was using was on the inexpensive side. My question is two-fold: What is opinion on this in general, then; if UV filters should always be kept on for protection, which ones do users recommend to avoid distortion and/or this effect, inexpensive or not? Thanks for comments.

[KentDub]

Hi Gerry,

Currently I don't own any filters for my dSLR. However, from having several filters with my video cameras I can tell you I only used them for two applications: 1) For the effect (i.e. ND filter, Polorizer, Warming ,etc.), or 2) For 'extreme' conditions (UV). I define 'extreme' as any situation you wouldn't want the end of your lens exposed to the elements. I have been very thankful for my UV filter when by the ocean or in sand dunes. I have also used it when it has been raining or snowing. For protection I rely more on the lend hoods (which arn't created equal btw), using the neck strap, and always being careful when the camera. "Sh*t happens", and you may want to follow the path of always using a filter - in that case, I would recommend a highend filter to match your highend lens. The quality of the light hitting the sensor is only as good as the weakest link.

[Gerry]

Thanks, Kent. That was my thinking, too, but thought I should check out my risk-taking!

[Amberglass]

Agrees with Kent. The controversy of use a protective filter or not is ongoing. But all it takes is one accident to put you in the situation of thinking oh "should've, could've, would've". Even with a hood it's not a guarantee that it will save your lens but does increases it's chances of surviving to a degree. I never bothered with protective filters until the day I broke my very first prime.

Beware that certain lenses requires/recommends a clear filter to complete it's weather and dust sealing, like the 24-105 f4L IS.

Two quality UV filters are B+W (Pro F) and Heliopan with multi-coating.

[KentDub]

Beware that certain lenses requires/recommends a clear filter to complete it's weather and dust sealing, like the 24-105 f4L IS.

Good to know! I actually have the 24-105mm F/4L IS (doh! it's in my signature).. This is probebly a stupid question - but in terms of weather sealing are all filters created equal? I thought I came across something that said the highend filters have more sealing or something like that.... hrm

[Amberglass]

Really poor quality filters will delaminate over time (cheap coatings) but the higher end ones won't. But the cheaper ones I have noticed will have a tendency to work themselves loose, even when properly tighten. Don't know why that is???

Never over tighten filters. Just give them a little twist in the end for snugness, but can be easily removed with a firm but gentle twist. If they ever get stuck from being on too long, just use a wide rubber band as a gripper.

I prefer B+W Pro F line UV haze MRC filter and the price has recently dropped. Never had an issue with glare, flare, soft images, and ghosting with them. Though for night cityscapes I do remove the filter and replace it with a FLW filter. You can get them here:

http://www.bhphotovideo.com/c/produc..._Haze_010.html

Oh neat little trick to prevent filters from sticking. With your index finger and thumb, pinch them together across your forehead to pick up some of your skin's oil. Now swirl your fingers around the outside threads of filter before screwing onto lens. Viola! No more stuck filters.

[Gerry]

Beware that certain lenses requires/recommends a clear filter to complete it's weather and dust sealing, like the 24-105 f4L IS.

Thanks for all the really good info! Amberglass, would you explain this a bit further? I am curious why canon would not recommend/require for all lenses, and, what is meant by "'complete' it's weather and dust sealing"? Thx.

[Colin Southern]

Thanks for all the really good info! Amberglass, would you explain this a bit further? I am curious why canon would not recommend/require for all lenses, and, what is meant by "'complete' it's weather and dust sealing"? Thx.

Hi Gerry,

Canon recommend it on some lenses (eg EF 16-35mm F2.8L USM). It's needed because there isn't a 100% seal between the front element and it's retaining ring, although I'm not sure why they don't can't seal it; I can only assume that it would introduce something undesireable.

To answer your original question, a quality UV filter - used for protection - will not cause any detectable loss of image quality ("IQ") under normal shooting conditions - they can however increase ghosting when shooting extreme contrast scenes (eg lights at night).

The issue seems to polarise people but personally I can't understand what all the fuss is about; we don't plan on having car accidents - and we're careful drivers - but we still wear seatbelts; same with our lenses. Having the filter attached provides an incredible degree of front-element protection, but is easily removed if required ... so the best of both worlds.

Keep in mind that, poor filter quality aside, the thing that you MUST remember to do if shooting RAW is to apply capture sharpening to your images; all RAW images will look soft will look soft when viewed at 100% unless capture sharpening is applied (can tell you more about this if you're interested). Generally an unsharp mask with an amount of 300% and radius of 0.3 pixels does the trick.

Hope this helps

[Gerry]

Thanks, Colin. I always appreciate your expertise. I shoot for stock sale and shoot Raw with no in-camera processing. I prefer to do all my processing in post and rarely sharpened my files at all since it's hard to get by with in stock. I am going to see if I can sharpen a small amount and get it approved. Is there any advantage to sharpening in-camera rather than in post? Does the soft thing apply when shooting jpeg also? It seems strange that I am just now noticing softness in my files at 100% on even much less.

[Colin Southern]

Thanks, Colin. I always appreciate your expertise. I shoot for stock sale and shoot Raw with no in-camera processing. I prefer to do all my processing in post and rarely sharpened my files at all since it's hard to get by with in stock. I am going to see if I can sharpen a small amount and get it approved. Is there any advantage to sharpening in-camera rather than in post? Does the soft thing apply when shooting jpeg also? It seems strange that I am just now noticing softness in my files at 100% on even much less.

Hi Gerry,

In a nutshell, in-camera sharpening is a "best guess" approach that may well be suitable for the likes of 6 x 4 prints from a photolab (ie "glorified P&S mode"), but it's never going to be optimal.

When you shoot RAW you're introducing softness from the digitization process it self - the anti-aliasing filter introcuces more - and the demosaicing process where full colour information is re-introduced adds even more.

To counter this we need capture sharpening, which is usually as easy and non-eventful as a USM of 300/0.3/0 (assuming a low ISO of 100/200).

Best way to see the effect (in Photoshop) is to double-click the zoom tool to zoom the image to 100% - open the Unsharp Mask dialog - dial in 300 / 0.3 / 0 and then toggle the preview control off and on several times whilst watching the result.

I can't understand why stock agencies would object to capture sharpening - in fact I'd be surprised if they would even notice. One way to find out

If you're interested, I wrote a bit about sharpening in another thread here.

Hope this helps

[Gerry]

Thanks, again, Colin. Will follow up on all.

[Amberglass]

Colin is right about the front moving elements and maintaining a seal. It's not just the 16-35 2.8 but the 17-40 4 as well.

I was told long ago by a college photographer instructor that "It's easier to seal a can than it is a jar.". Moving parts can be sealed but difficult to maintain, eventually the seals will go (they're made of rubber), hence the recommendation for a PF. Internally focusing lenses like a can are easily sealed obviously from the lack of moving parts.

Note that Canon says "water resistant" to certain lenses while others, like the 70-200 2.8 and above, are labeled "highly resistant" to dust and moisture.

To maintain the "M&D resistant" seals besides a PF, it's best to store your glass in a cool dry environment. Always give your gear time to acclimate to temperature extremes by living them in your gear bag for at least 20 mins before using to avoid condensation build up within and drying out of seals.

If properly cared for, your lenses will last you pretty much for years to come. My oldest Canon lens is 25 years old. An oldie but goodie.

You can actually do this to your camera (with the proper seals on lenses and bodies). FYI, do not do this with entry level bodies. Please read your manuals about conditions of weather sealing on your gear, enjoy:http://www.youtube.com/watch?v=iYXtvTFLCa4

[Colin Southern]

You can actually do this to your camera any camera with the proper seals on lenses and bodies, enjoy:
http://www.youtube.com/watch?v=iYXtvTFLCa4

As a Canon shooter, I'd just LOVE to try that on a Nikon camera (any volunteers?)

[Amberglass]

As a Canon shooter, I'd just LOVE to try that on a Nikon camera (any volunteers?)

Too late Colin. I got tidal waved while shooting a on boat once this past summer, and I attest that my D700 and 24-70 2.8 held up beautifully. Your turn Colin and your Canon.

[Gerry]

I'll sit this one out with my li'l Rebel.

[Dave Humphries]

As a Canon shooter, I'd just LOVE to try that on a Nikon camera (any volunteers?)

That was a Nikon camera, so our case is proven, time for you to prove it with a Canon 1DS3 (or whatever it's called) and an L series

Time to put your mint sauce where your camera is!

(I dunno, mint sauce seemed more appropriate than apple sauce with all the lamb you have)

[Colin Southern]

That was a Nikon camera, so our case is proven, time for you to prove it with a Canon 1DS3 (or whatever it's called) and an L series

Time to put your mint sauce where your camera is!

(I dunno, mint sauce seemed more appropriate than apple sauce with all the lamb you have)

Perhaps this is the fundamental difference between Nikon & Canon shooters; we Canon shooters aren't daft enough to do it (bit like crashing your car to prove that the airbags work!).

[Andy]

Perhaps this is the fundamental difference between Nikon & Canon shooters; we Canon shooters aren't daft enough to do it (bit like crashing your car to prove that the airbags work!).

Can't see the youtube link from work but my cameras have been soaked loads of times. Mostly by rain as it rains a lot in Scotland but they have also been soaked by salt water while hanging over the side of a boat to photograph dolphins and sitting at the bottom of waterpark flumes.

It's an EOS 3 with 100mm macro below but I used a 300D for over a year in all sorts of weather and it was fine. So long as I can keep the viewfinder and front element clear to shoot through rain or spray doesn't bother me - there's only so much water that will stick on a camera before it runs off....


I rarely use camera bags - most of the time I go out with the camera round my neck with the lens I plan on using. If it rains the camera gets wet.

Folk often bang on about weather sealing like it's really important. I used to think that too until I proved to myself that even my 300D could cope fine with rain.

Anybody ever had a DSLR or lens stop working because it got wet?

[Amberglass]

The biggest concern for moisture (condensation) getting into your gear over long term exposure is "fungus" (more commonly known as lens rot) growing inside the body and lens. It's can very aggressive and contaminate neighboring gear. Camera manufacturers have always recommended and stated that one should keep their gear stored in a dry cool environment.

If you should see fungus growing in your gear, double bag it in plastic and have the camera sent out to be professional cleaned. Otherwise it will come back time and time again when the humidity is right. Towel drying then cleaning your lens with alcohol, and wet cleaning your sensor will not get rid of it.

I store my gear in an air tight pelican case and use silica gel drying crystals to dry out my gear completely after a day of shooting in rain. Toweling off the exterior of course. Here's a link to the reusable SGC packs if anyone is interested: http://www.pelican-case.com/15peldessilg.html

Here's an image of what it looks like: http://www.wind.dk/photographs/weird...nFD50mm1.8.jpg
http://static.photo.net/attachments/...8-25801284.jpg

[Blazing fire]

Just like to share some information about how people living in humid environments, like in the tropics, prevent growth of fungus.

They use a dry cabinet instead of a dry box to prevent growth of fungus. The former is a maintence-free solution although it reduces the humidity levels slower. If really low R.H values are required, they place silica gel into the dry box. Cameras and lens are stored in dry cabinets/boxes when not in used. They also recommend a RH of no lower than 45% because too low a R.H may dry up the lubricant.