Does one put a protective UV filter on a large format lens (4x5), like in 35mm? I think this is an obvious yes question, but I recall reading that when using filters on large format lenses, for the filter coverage to work the filter is 4x5 inches. Excuse my ignorance, I have not yet educated myself on this particular subject.

-- Raven (mtand13@netreach.net), April 09, 2000

Answers

Response to UV filter

I never do. I do not even own a UV filter. When I need UV penetration, I use a light or medium yellow filter. 35mm camera are often used in ways that require lens protection. The way large format cameras are used, lens protection is usually unnecessary.

-- William Marderness (wmarderness@hotmail.com), April 09, 2000.

Response to UV filter

The filter does not need to be 4x5 inches. A standard screw in filter will do.

-- William Marderness (wmarderness@hotmail.com), April 09, 2000.

Response to UV filter

Although not required, I use them on all my lenses. But because mine get banged around a lot in the field, they are very important... in a few situations shooting by large water falls, the wind would blow some water mist and get on the UV filter... something in the mist ruined my $75 glass UV filters... they were permanetly damaged... I am not sure had I not had the filter on, that it would have ruined my $2000 lens? But I do not want to find out either... so a lot of the answer revolves around what risks you confront with your lenses? You use normal screw in filters, just like 35mm as William mentioned...

-- Bill Glickman (bglick@pclv.com), April 10, 2000.

Response to UV filter

There's a school of thought that any filter attached to a lens degrades the image quality slightly, and I must admit that I've personally seen evidence to support this when using long lenses with 35mm. Since the main reason to use larger formats is for better image quality, it would seem counter-productive to compromise it with an unnecessary extra piece of glass. Sometimes, as Bill pointed out, a filter's a necessity to protect the lens, but in most circumstances a lens cap does the same job. Large format cameras are rarely carried about with the lens in place, and (almost) never worn around the neck, so there isn't the same need for an "accident" filter.

-- Pete Andrews (p.l.andrews@bham.ac.uk), April 10, 2000.

Response to UV filter

When using electronic flash and doing color critical work, as in fine art reprography, a UV16 filter is an absolute must!

-- Tony Novak-Clifford (photoho@mauigateway.com), April 10, 2000.

Response to UV filter

" Sometimes, as Bill pointed out, a filter's a necessity to protect the lens, but in most circumstances a lens cap does the same job. Large format cameras are rarely carried about with the lens in place, and (almost) never worn around the neck, so there isn't the same need for an "accident" filter. "

Ever shoot at the beach, in the snow, in the rain, etc.?

There are many places and ways to shoot where things can happen to a lens while shooting and leaving the lens cap on while shooting is usually counter productive.

-- Bob Salomon (bobsalomon@mindspring.com), April 10, 2000.

Response to UV filter

Raven: Filters can indeed protect the lens on LF cameras. One of the major reasons for using LF is that a tiny bit of image degradation caused by a filter doesn't make any difference. The enlargment factor is so small that you won't notice any difference in the images. It is not like 35mm. Too many people try to put 35mm standards on LF. Look at many LF lenses and you will notice a lot of dinged front lens mounts. I much prefer to ding a filter ring. Also, you don't degrade a lens by constant cleaning. If you get a cleaning scratch on a filter, toss it and get another. I personally carry a camera a lot with a lens in place when I am shooting. I will not take the time to remove a lens, put in the bag, and close my camera when I am moving around an area shooting. I keep a light yellow filter on my lenses most of the time. I can swap it for a deeper yellow or another color if I need to, and the filter protects the lens. Doug.

-- Doug Paramore (dougmary@alanet.com), April 10, 2000.

Response to UV filter

Bob: Rain or snow landing on a filter will ruin a shot just as much as it would on the front element of the lens. A deep lenshood would be more appropriate in those circumstances. I'd class a beach as a hostile environment and would certainly fit a UV filter.

Would you suggest fitting UV filters to the rear of LF lenses as well? I'd say lenses are more at risk when being fitted or removed from the camera than at any other time, and it's going to be the exposed rear element that's likely to get scraped on the front standard, or dinged by a fall if anything.

I've seen many posts in this forum agonising over the tiniest difference in the MTF curves of lenses. Are you suggesting that the expensive bit of extra contrast or resolution that your customers have paid for isn't important after all?

-- Pete Andrews (p.l.andrews@bham.ac.uk), April 11, 2000.

Response to UV filter

Anything falling on a lens requires that you clean the stuff off.

Constant cleaning is more likely to effect the final quality of the image then a good filter would.

Additionally filters reduce the quality of the resolution on very, very long lenses only, unless the filter is grossly defective or used behind the lens. A quality filter placed in front of a lens will not effect the resolution of a view camera optic.

-- Bob Salomon (bobsalomon@mindspring.com), April 11, 2000.

Response to UV filter

Pete: I have never had a customer ask to see the MTF curve of my lenses to determine if they should purchase a photograph from me. As for me, I have never studied MTF curves, wouldn't understand them if I did, and I don't really give much of a damn about numbers. I suspect that folks who agonize too much about such things are more into impressing the peasants with their cameras and lenses than in making photographs. The tiniest bit of extra contrast and sharpness means little unless you are doing some specialized bit of scientific photography or such. For most photography, a photograph which pleases the customer and makes him or her shell out the money must meet three criteria: These are: (1) Subject. (2) Subject. (3) Subject. As for me, I will let Schnieder, Nikon, Rodenstock, Fuji and others worry about such things as MTF curves and numbers. I prefer to spend time making photographs with my mixture to classic, just plain old, and newer lenses which I know work well if I do my part.

-- Doug Paramore (dougmary@alanet.com), April 11, 2000.

Response to UV filter

Good grief! I didn't realise it was so heretical to suggest that filters degrade a lenses performance.

There's simply no denying that contrast is reduced by adding a filter, multi-coated or otherwise. And it's not just with very, very long lenses that resolution is affected. The effect of putting a slab of glass in front of a lens is to introduce a small amount of zonal spherical abberation, together with chromatic and other errors. This increases with the thickness of the glass, the diameter of the lens and the closeness of fosussing distance. Admittedly, in normal distance photography with a thin filter and a small physical aperture the effect is diminishingly small. But in close-up and macro photography a thick filter like a polarizer can ruin the definition of the lens.

-- Pete Andrews (p.l.andrews@bham.ac.uk), April 12, 2000.

Response to UV filter

"This increases with the thickness of the glass, the diameter of the lens and the closeness of fosussing distance. Admittedly, in normal distance photography with a thin filter and a small physical aperture the effect is diminishingly small. But in close-up and macro photography a thick filter like a polarizer can ruin the definition of the lens. "

Even more important is the flatness of the filter and good filters are very flat and have negligible effect.

Poor filters will have a very definite effect.

-- Bob Salomon (bobsalomon@mindspring.com), April 12, 2000.

Response to UV filter

No, Bob. It doesn't matter how perfectly flat the sheet of glass is, this is simply a matter of light rays being deviated from their normal straight-line path in air by meeting a material of different refractive index. If you take the case of a slightly off-axis point in a subject plane close to the lens; there's no deviation of the ray of light where it hits normal to the filter, and it will carry on to meet the lens at the same point as without the filter. At any other point on the filter the rays will be more deviated, and meet the lens at an abnormal angle. This has the effect of shifting the focus of those rays slightly away from rays closer to the normal point. The result is indistinguishable from a lens with an incorrect front element curvature, and gives rise to zonal spherical abberation. The distance travelled through the filter also varies with the angle that the ray meets it at, and the chromatic dispersion changes across the diameter of the lens as well.

So you see, for subjects relatively close to the lens, the thickness of the filter is just as important as its flatness.

-- Pete Andrews (p.l.andrews@bham.ac.uk), April 12, 2000.

Response to UV filter

Pete,

The most common problem with poor filters is that they are not plane parallel and create a loss of resolution.

High end filters do not have this problem.

-- Bob Salomon (bobsalomon@mindspring.com), April 12, 2000.