So, I've got some 0% financing and I'm doing some research for my next lens purchase....I figure I was going to get it for my birthday in November anyways...I might as well finance it now and enjoy it all summer, right?
Anywho, I stumble into this great post while researching my two lens choices. For those that don't know, Thom Hogan writes comprehensive Nikon books, teaches, and is a great all around photographer that specializes in outdoor shooting.
> Does anyone have any _ scientific _ data on this?
No, but I can add some anecdotal evidence. I have never used protective filters in now 40 years of shooting. In that time, I've damaged one lens' front element (and my treasured 70-180mm, at that) by managing to scrape something against the front element and damage the coating. I could not detect any difference in performance of the lens after the small scratch, but I had the front element replaced, anyway.
In teaching workshops for the last decade, I've had hundreds of students crawling over the landscape with me. I'm not aware of any of them having damaged the front element of their lens, either.
I think a lot of the discussion really boils down to "prudent care" versus "I don't want to pay any attention." The most serious shooters pay prudent care to what they're doing and what they're exposing their equipment to. The might take a chance, but it's a calculated chance. They use lens hoods. They sometimes are using other filters for effect (grad, polarizer, etc.). They're not perfect. They make mistakes (drop equipment, etc.) but understand that this happens and that you pay to have it fixed in order to get back to 100% capability.
The truly casual shooter has a different attitude. I got an email the other day from someone who bought an expensive lens and wanted to know what protective filter to buy. He even included "and don't tell me to use a lens hood, because I never bother to, it's too much trouble." Well, I have to question why he bought an expensive lens, then. It seems really silly to buy a top grade lens and then start doing things that will compromise what it can produce. I did a quick test on my charts: he would get better MTF results with the 18-55mm VR with hood and without filters than he would with the expensive lens he purchased without hood and with the $20 filter I pulled out of my closet (I don't even know why I have it, but it was there so I tried it). So what we know about this case is that the person is more worried about protecting their "investment" in gear than producing the kinds of images it is capable of.
The curious thing is that the same casual shooter will think nothing about using something like a G10 or P6000 without a protective filter. This tells us something about the genesis of the "protective filter requirement." If a camera doesn't easily take filters, stores don't make the pitch that "you need a protective filter with that." If it does, they do, and mostly because it allows them to up their margin on the sale. Once the notion is in someone's head, they don't challenge it and it lives on for all their other lens purchases.
My philosophy is this: if you bought a DSLR and lens because you wanted high quality images, then you don't do things to compromise that quality. That includes adding two air/glass surfaces that will remove 5% of your contrast. If you're more worried about the cost of replacing or repairing your equipment than your photos, then do what you want and add ten filters to your lens (after all, if one filter protects against modest impacts, two would protect against a harder impact, and three against an even harder impact... ;~).
author, Complete Guides to Nikon bodies (19 and counting)