Using Behind the Lens Filters

[Drew Wiley]

Gosh, why on earth use fragile gels now that they're often more expensive than top quality coated glass filters?? Of course, I'm referring to real Wratten
gels and not polyester filters which degrade the image even more. But I get a kick out of all these references to old ways of doing things that were once allegedly produced perfect results, but now would look iffy side-by-side with prints taking advantage of decades of learning curve. Go back far enough and
Alley Oop was perfectly healthy and happy not even cooking his meat. My eyes can immediately tell when there are fingerprints or other smudges on my sunglasses. Don't tell me there is no effect.

[cdavis324]

Gosh, why on earth use fragile gels now that they're often more expensive than top quality coated glass filters?? Of course, I'm referring to real Wratten
gels and not polyester filters which degrade the image even more. But I get a kick out of all these references to old ways of doing things that were once allegedly produced perfect results, but now would look iffy side-by-side with prints taking advantage of decades of learning curve. Go back far enough and
Alley Oop was perfectly healthy and happy not even cooking his meat. My eyes can immediately tell when there are fingerprints or other smudges on my sunglasses. Don't tell me there is no effect.

If it's that obvious, you must have examples to show!

Sent from my LM-V350 using Tapatalk

[Drew Wiley]

Well, that kind of thing does make a difference. It's one of the first things I learned when making prints. Then I found it highly ironic that photographers would go to considerable expense and into nitpicky arguments about the very best lenses, then defeat the whole point by putting a junky or dirty filter over the lens (admittedly, not as bad as doing the same behind the lens). This is really just common sense. Is your view driving down the road as equally clear with smeared bugs and grime over the windshield as when it is clean?

[consummate_fritterer]

I agree that damaged filters affect image quality. I have serious doubts that a single gel filter in new condition placed behind the lens noticeably adversely affects image quality without using lab grade measurement devices.

[Pere Casals]

I agree that damaged filters affect image quality. I have serious doubts that a single gel filter in new condition placed behind the lens noticeably adversely affects image quality without using lab grade measurement devices.

In theory, if the lens is single coated it would generate some flare, of around 5% of the total incoming light. If it is a multicoated lens that flare would not be noticed, because the light that the gel reflects to the front it won't be much reflected back again by the multicoated surfaces.

Regarding Image Quality, possibly a wide angular lens would notice more the gel, because the rays are more angled. This is in theory, it would be good to check it in practice...

[Drew Wiley]

There's no substitute for a lens hood or other effective shade. Flare can occur even with multicoated optics, or conversely be brought to a minimum using lesser optics which are effectively shaded from unwanted light. But oh my, Pere and Mr. Fritterer, you both abound in untested theory. Kinda like the annual running of the bulls in Spain. I'm certainly not smarter; but one does remember a thing or two after being gored and trampled by the bulls over the years. And in my case, having lugged very heavy packs for days on end into remote places I probably will never see again, losing a special image or having it compromised was indeed disappointing. Back then I tended to print big highly-detailed Cibachromes; and some things which seem to be matters of mere opinion on these web forums were plain as day under those kind of stringent darkroom expectations. I have nothing against breaking the "rules" on purpose, or softening images for esthetic reasons; but
misinformation has the potential of producing unwanted effects.

[consummate_fritterer]

It's true it's been awhile for me, Drew, but I'm not entirely unpracticed in the field.

[Pere Casals]

There's no substitute for a lens hood or other effective shades.....

Drew, of course

Anyway it is interesting to guess when a gel behind the lens produces some flare

[Drew Wiley]

Well, sometimes it doesn't matter. I remember running into a stock photographer with a beat-up 4x5 Tachi, seven lenses, and a stack of at least twenty Wratten gels, all of them roughed up and with masking tape markings. It was nearing sunset below Fremont Peak in Wyoming. I got my shot and packed up and left while he was still fiddling around with too many gear choices, and it went dark before he could get a shot. But back then large format color images still yielded decent stock fees, yet many of them were printed even smaller than the original 4x5 film image. Even a cover shot would only equate to 2X or so enlargement. And just this month the Postal Service is going to release a whole sheet of stamps based on the work of a local color landscape photographer. Forgot his name - it's awfully "scenic" stuff; but he uses pro equipment. So in those kinds of cases, potentially paying ones bills for the duration of a career, minor discrepancies in sharpness aren't even going to show, much less in the case of some portrait studio which routinely employs Softar filters or the equivalent. But most of my game involves very crisp images - not "sharpness for sharpness' sake", but as a contributory tool within a certain kind of look
I'm known for. It's not the only kind of image I make, but one I've gotten good at.

[consummate_fritterer]

Drew, do you have any comparisons of using any kind of single filter in front vs. a like-new gel of the same type, behind the lens?