Filters vs Lens Performance

[bento2]

Iv'e seen many posts on the internet regarding effect of filters on the Canon 100-400 L zoom.

Will a Canon clear protector filter really degrade my lens?

Thanks

[ebiggs1]

I have both the 100-400mm and the 400mm f5.6 prime.  I am guessing people may be seeing a slight difference in the prime vs the zoom and maybe they blame the filter.  Ironicly, as I am a promoter of protector filter use, I have none on eihter of these two lenses. Which makes it impossibile for me to say with any authority.

For some reason, some folks give the 100-400mm a bad wrap. And it is highly undesereved!

As for any comparision between the zoom vs the prime, my choice is the 100-400mm because it has IS where the prime does not. And in this case I would rather have the IS than not.  Other things being more or less equal.

It is my observation that zooms of this type are used way more at the long end than they ever do the short end.

[TCampbell]

While I don't have UV filters on my lenses, I do own them.   But I've done some comparisons and had planned to make a video (haven't done that yet) to visually show the difference in filters.

In astronomy, some catadioptric telescopes have anti-reflective coatings on them, and others do not -- and this is when I first started to notice the difference.  On an uncoated telescope, the front "corrector plate" (basically a lens but it looks rather flat even though it actually does have a shape that bends light) is somewhat reflective.  Stand in front of the scope and shine a bright light on yourself (not the scope) and you can see your reflection in the glass.

But if you do the same experiment with a scope that does have the anti-reflective coatings, you can barely see any reflection.  The difference is VERY noticeable.  

All glass reflects some light that hits the surface of the glass.  If it didn't reflect any light at all, you would not be able to see the glass -- it would be invisible.)  A stronger reflection means it's reflecting a lot of light rather than transmitting it through.  A weak reflection means more light is transmitting through and very little is reflecting.

With that concept established, I grabbed two of my UV filters to compare:

1)  Tiffen UV Protector filter.  The box claims "The UV Protector helps protect your camera or camcorder lens against dust, moisture, fingerprints, scratches, and damage.  It also provides basic reduction of UV light.  This filter may be kept on your camera at all times."

If I turn on a desk lamp, then use the filter like a mirror... I see a fairly STRONG reflection of that lamp in the glass filter.  Incidentally, it's possible to coat one side and not the other -- so I did test both sides of the filter in the event that one side had coatings which were not present on the other side -- but saw no difference in reflectivity.

2)  B+W Brand Digital MRC UV-HAZE filter.   The difference here is astonishing.  I could see a reflection of the lamp... but it was VERY weak.  Both front and rear sides have an extremely weak reflection.

If I hold both filters over a black surface, the Tiffen filter is readily visible as a piece of glass... but sitting next to the B+W brand coated filter... the coated filter almost appears to be missing it's glass (technically a reflection is there, but the difference between the two side-by-side almost makes the brain think I've just place the empty filter ring there with no glass on it.

I have seen a LOT of ruined images caused by "ghosting" and reflections from the filter.  Light passes through the filter.  Some reflects off your first lens element (true lens element) and back to the filter.  Since that filter is "flat" it simply "reflects the reflection" right back into the camera again -- and you get ghosting and odd reflections in your image.

Tiffen's claims are basically all true -- of course they don't mention that negative effects of using a filter.  You are far more likely to notice the effect of flare and ghosting caused by the extra filter than you are to notice the effects of a smudge or dirt spec on the front of your lens (or even a scratch).  

As one more experiment... I grabbed a 3M post-it note and cut it down to just a few square millimeters and stuck this on the front of my lens to "simulate" a big piece of dirt on my lens.   Then I took a photo.  I could NOT see the spot in my image.  I found that if I made a large enough square (I made some of various sizes) then eventually I would notice a dim area in my image (even though I couldn't see the piece of paper at all.)  

Lesson learned:  If you're going to use a filter, use a GOOD filter and make sure it has anti-reflective coatings.

[cale_kat]

This discussion of clear filters, IMHO, is the equivalent of arguing what sort of screen door makes a difference on a submarine. Photons are going to rush into the lens with the same urgency as water into a submarine regardless to the "fineness" of the screen.

What is telling, is that there is no visual evidence offered to support that a clear B+W filter changes the visual context of an image vs a Hoya filter or no filter at all.

[RobertTheFat]

Use your lens cap to protect the lens. That's what it's for. Most of the damage that a lens suffers happens when the lens cap could have been on it.

That said, I was once photographing a cocktail hour event at work and couldn't resist sampling the hors d'oeuvres. Only an hour later, after many more shots, did I discover that I had immersed the front element of my lens in sour cream dip. But I learned my lesson (Don't eat during a photo shoot), and the lens cleaned up OK afterwards.

Another lesson from the experience is that it takes a lot to seriously degrade a len's performance. All the time the sour cream was on my lens, I had been looking through it and hadn't noticed that anything was wrong.

[cale_kat]

There are threads on the end of the lens to attach things. (No worries, that thing probably has thread to attach a lens cap so you can keep your thing safe. 🙂

[bento2]

Many thanks to all who replied to my query - far more response than I anticipated!

I always have the lens hood on my 100-400, so maybe I will just kkeep going down that path without a filter attached.

It's a great lens, so far the only problems with performance have been the result of user error - like forgetting that the 400mm setting is more like 640mm on my 7D and having too slow shuitter speed.

Thanks again!

[amfoto1]

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@cale_kat wrote:

...there is no visual evidence offered to support that a clear B+W filter changes the visual context of an image vs a Hoya filter or no filter at all.

---

Yes, there is plenty of visual evidence if you just take the time to look for it (or do your own tests).

Here's one example I was able to go back and locate quickly: http://photography-on-the.net/forum/showthread.php?t=1199661

LH image, no filter. Center image, a high quality, multi-coated Hoya HD clear filter shows a bit lower constrast and some loss of fine detail... though not too bad. And RH image with generic, uncoated or single coated UV filter shows significant loss of IQ.

Here's another example comparing with and without a moderately high quality Hoya UV HMC on the 100-400: http://forum.weatherzone.com.au/ubbthreads.php/topics/277584/Filter_problems

If you look, you'll find more examples and a lot of discussions. I've seen this repeated time and time again in general... and a lot for this particular lens, which enjoys a very nice, deep built-in hood making a protection filter largely redundant anyway.

But, hey, if it makes you feel more comfortable taking the lens out and shooting with it, put a protection filter on it.

Sometimes I work in places where there's risk of something falling on my head, so I have and wear a hard hat at those times. But I don't wear it 24/7/365.

***********
Alan Myers

San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM 

[cale_kat]

One photographer, one lens, repeat twice and you get two hotheads. Let them shoot their 100-400's without filter.

You would be mistaken to think that this is evidence but if you're so easily impressed, so be it.

I remain unconvinced.

[ebiggs1]

“The simple answer is "yes", adding any filter to your lens will degrade the image to some extent.”

“Yes, there is plenty of visual evidence if you just take the time to look for it (or do your own tests).”

The correct answer to the first statement is, yeah it will, at least in a laboratory. The correct answer to the second statement is not nearly so cut and dry. For one point, it depends on how you intend to show your work.

The agreed upon “degrade” is closely tied to that fact.

Take time to “do your own tests”? OK here is a shot I was about to delete but decided it was a good example to show exactly what is a real world situation. Nothing going for it and a lot not optimal, to say the least.

This photo could not have had any worse conditions to shoot with. Unless it was raining, I guess.

This was taken with my 120-300mm f2.8 zoom lens. Yes this photo has a filter on the lens. And in addition it had a 1.4x tele converter! In addition I was walking and it is hand held. Look for yourselves. Would this do for Facebook? Would it print?

Can you pixel peep it? Is any body going to say if only it didn't have a filter on it. Here is a 100% crop and better yet a 200% crop. That is about as tough as it gets for scrutiny.

I am not wanting any critical acclaim, this is just an example. Make up your own mind.

[amfoto1]

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@bento2 wrote:

Iv'e seen many posts on the internet regarding effect of filters on the Canon 100-400 L zoom.

Will a Canon clear protector filter really degrade my lens?

Thanks

---

The simple answer is "yes", adding any filter to your lens will degrade the image to some extent.

I do not have the 100-400 personally, but have used it (never with any filter, that I can recall) and have friends who own and use it a lot. I have no idea exactly why, but particular lens seems to not "play well" with filters.

I'm basing this on repeatedly seeing many posts on other forums where people bought one, then complained of softness in the 100-400, particularly in the 300-400mm range. Asked if they were using a filter, when they said "yes" and were told to remove it and reshoot their tests, they were stunned at how their image quality improved. I've probably seen this sequence reoccur 50X, 100X and it doesn't seem to matter a great how good quality the filter (though cheaper single coated or uncoated likely will be worse).

Besides, the 100-400 has a really nice, deep built-in lens hood that will protect the lens better while shooting than any thin piece of glass ever could. When stored, the lens cap will provide excellent protection.

I am not a "filter hater". I do have protective filters for all my lenses that can be fitted with a filter. (A couple of my most expensive lenses cannot, but thankfully have very keep lens hoods). I keep those filters stored in my camera bag for the times when using one is advisable... such as shooting right next to a dirt race track or arena, or out in a sand storm, or at a paint ball contest, yada, yada. I might use one if shooting around sticky fingered children or wet nosed puppies, too. I usually use one when shooting at the coast, since salt spray is particularly nasty stuff and hard to clean off glass. I'd rather rinse it off a filter than try to wipe it off the lens optics!

But 99.5% of the time my lenses don't have a protection filter on them. Been that way for decades in some cases, without any problems. Rather than a protection filter, I'm actually far more likely to use a polarizer or neutral density or one of several filters I like to use for portraiture... which give enhancements to my images that outweigh any slight loss of IQ from the addition of a high quality filter. But there are still some situations where I always avoid a filter... such as shooting a sunset... where there is strong specular light in the image.

Some might suggest that, hey, you can always remove the filter if and when IQ is a concern. That's true. But, yeah, like I'm gonna stop shooting thinking, "Hey, this is going to be one of my best shots ever and I really want to make sure it's perfect.... I'd better remove that protection filter". By the time it occurs to me, I'm done unscrewing the filter and tucking it away in my camera bag, the photographic moment will nearly always be long gone. To me it makes a whole lot more sense to do the exact opposite... to pause on those infrequent occasions when I'm shooting next to a dirt race track... or out in a sandstorm... or next to the ocean surf, etc... and think "Hey I'd better protect my lens." and then add the filter.

Try it for yourself. Buy a high quality, multi-coated protection filter such as a Hoya HD2 or B+W MRC or similar. I've heard good things about Marumi, but haven't used them personally. (Sorry Canon...I didn't list your filters, because as best as I can tell, they are not multi-coated, though they're typically priced as high or higher than other manufacturers' top quality filters that are).

It certainly won't hurt to have one available, just in case. Take some careful comparison shots using the lens with and without the filter. If you're okay with the loss of IQ and having a thin piece of glass in front of it means you'll be more comfortable taking your new lens out to shoot with it, great! If you aren't happy with the IQ, you might want to store the filter separately but keep it handy for those occasional times when it's really needed.

But also be realistic. I've seen more than a few lenses damaged by broken filters, too. After all, it's just a thin piece of glass and should it get shattered when struck by something, the sharp shards can be driven into the front element of the lens, scratching it. Might or might not have fared better without any filter. Who knows... but today's lenses are pretty tough. Anyway, when using a filter, it becomes even more important to also use a lens hood, to protect both lens and filter from possible damage and from oblique light.  Using the lens hood while shooting (and the lens cap when not) certainly can never harm IQ...  and will give better protection than any filter ever could.

***********
Alan Myers

San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM