The equivalent of a reverse center filter

[psychophoto]

This is a "does it exist" question more than anything else. I'm thinking of a filter that is

the functional opposite of the type of center filter used on wide angle lenses for large

format cameras to correct for light fall-off. Center filters are darkest in the center and

graduate to clear on the outer edge and help even out exposure across the film. This filter

would do the opposite. That is, the filter I'm thinking of would actually

induce light fall-off towards the edges of the frame while leaving the center portion

unaffected. So

yeah....does it exist?

[cole_petersburg]

Oh, yah!<BR>

It's called a lens hood. Get a lens hood for a long lens and put it on a normal lens. For a more graduated look, just get a very, very old lens.<BR>

If you have a Lubitel, crank the aperture control all the way to f/64. Just kidding - you don't have to do anything to achieve this effect with a Lubitel!

[rokkor fan]

Just buy a Lomo

[jbq]

As was said, use any lens that doesn't have quite enough coverage (or that is known for it falloff).

 

You can e.g. use a lens designed for small-sensor DSLRs on film.

 

You can use a lend hood too long for the lens you use.

 

You can use a lomo lc-a or lubitel (my lubitel 166U has a ton of falloff when shooting 6x6) or a holga (same thing, 6x6).

 

Or you can experiment cutting rings out of matte black paper and attaching them at the front (or rear) of your lens. That's probably easiest as it will give you the most control. Results may vary a lot depending on the individual lenses, best results probably coming from longer lenses.

[kelly_flanigan1]

In some movie stuff for showing what glacoma does to a person; we used a black matte paper; with a star cut out of the center; with a mess of "points". Another way is to use a UV/Skylight/clear filter; and "chicken peck" the outer parts; with a 6x0 or 4x0; 3x0; etc KOH-I-NOOR technical pen; with black india ink. One wants more "pecks"/dots at the outer rim; an less at the 1/2 toward the center radii. Avoid doing this directly on you new Panavision; Zeiss; Summicron or Nikkor front surface:) A tiny; very very tiny felt tip black pen works; BUT many times they fade due to UV; or outgassing. A carbon black technical pen ink is WAY more robust in fade resistance. On a simple camera; a piece of microscope glass or window pane scrap can be used; held; taped close to the lens. With a simple P&S digital; with a 5 to 13mm lens; the dots need to be real small. The lens can actuall focus on the front surface; or filter; in bright sun; ie stop down conditions.

[bacsa]

although somewhat different approach, check my latest <a href="http://www.photo.net/photodb/photo?topic_id=1481&msg_id=008yYC&photo_id=2558807&photo_sel_index=0">experiments</a>.

[alex_lofquist]

Some wide angle lenses for large format came with front filter to reduce the light at the center of the image. You might just be lucky to find one at a swap meet.

[bacsa]

alex:))

[psychophoto]

So.....I'm guessing this means that as far as anyone here knows, such a filter does not

actually exist. Vignettes, lomos, long hoods, etc are all well and good but do not

accomplish what I am looking for. Using a technical pen on an old UV filter is closer, as it

would reduce exposure towards the edges of the frame to any extent I wanted, really, but

it also adds the factor of diffusion, which I do not want. Exposure reduction yes, anything

else, no. No black edges or cut-off corners, no diffusion. Such a thing would be pretty

easy for a filter manufacturer to make, but at this point I'm guessing that nobody actually

makes it.

[bacsa]

Well, I think Schott, Schneider, Carl Zeiss and some others do make special filters just for you if you ask for it:) Not too cheap, of course;)

 

Is photoshop not an option?

[jbq]

David: another (easy) solution is to make your own filter using medium or large-format film (depending on the size of your lens). Create the pattern that you're interested in, e.g. by displaying if on your monitor or printing it, and take a picture of it out-of-focus on a B&W film with a reasonably clear base.

 

Or, if you shoot B&W, you can do the same thing with slide film (with a reversed pattern, of course).

 

Looking at the characteristic curve of TP (I picked 6 minutes in D76 at 68F), it appears that a 4-stop contrast range in the original image (approx -1.7 to -0.5 lux.s) will get you about a 3-stop difference between the center and the edges (approx density from 0.1 to 1.0).

[neil_parker]

This is dead-simple to achieve with a circular gradient mask in photoshop and completely

controllable. Why look for a hardware solution? In the 'old days' this was done with a

vignetting mask or by burning the edges in the darkroom.

[al_kaplan1]

There was a company, Cokin, about 25 years ago that made these along with a lot of other special effects filters. These were popular with wedding/portrait photographers. The filters were cheap plastic and fit in slots in a big holder. They came in different colors and shapes of openings.

[rokkor fan]

The Cokin filters would not assist with this issue. There is a centre spot Cokin filter that has a grey (or other colour) surround with a clear centre BUT the Cokin filter also has a built in diffuser in the colored (ie. grey) area. This means the outer vignetted area is also soft, and would not meet your needs.

[dan flanders]

The old time commercial photogs knew how to do it. Here's a print made sometime around 1880. I just don't know how it was done.

[dan flanders]

Sorry,it didn't work. I'll try again when I'm sure I can do it.