center filter needed?

rob_rielly · February 9, 2000

I have a suuper angulon f8 lens that I have not used much. I do plan to use it on an upcoming trip (landscapes). Will I be able to get away without a center filter, or do I really need to pick one up? Thanks for the advice. Rob

michael_briggs2 · February 9, 2000

Some additional information would help us answer your question: what

focal length lens and what size film?

There are some similar questions (with answers) under Older Messages:

Filters.

--Michael

lester_moore1 · February 9, 2000

I use a Nikon 90mm f/8 for 4X5 landscapes. I have never experienced

vignetting, even when using a lot of camera movement. In contrast,

the 75mm I used to rent had noticeable vignetting, even with moderate

movements. Almost all of my images were shot at f/22 to f/45.

bob_salomon3 · February 10, 2000

All modern wide angles have similar fall off. If someone claims

their's does not then the subjects they photograph are dark enough on

the edges to mask the fall off or they dodge and burn in printing or

overlight the edges of the scene.

ZDo you need one?

It depends on what you shoot and how you shoot.

You are the only one that can answer your question. If in doubt buy

the filter.

pete_andrews · February 10, 2000

It's not just a modern problem!

When the Zeiss Topogon was introduced in the 19th Century, it had such

an extreme angle of view that fall-off had to be corrected.

Unfortunately the technology didn't exist to make graduated glass

filters back then. The elegant solution was a little black metal

foil "star" on a needle-like axle that was placed directly in front of

the lens and rapidly spun round during the exposure, thus shading the

centre more than the edges. The device wasn't powered in any way, I

think the photographer had to blow sideways across the thing to set it

spinning, presumably being careful not to spit!

Sorry for my little diversion down the forgotten byways of technology.

I just thought that the idea of a little spinning star in front of a

lens might amuse you as much as it amused me.

pete_andrews · February 10, 2000

Correction to the above.

It was the Goerz Hypergon that had the little star gizmo, and it was

made in the early years of the 20th century.

Apparently a 75mm version covers 10"x8" !!!

Anyone got one they don't want in an attic somewhere?

simon2 · February 10, 2000

I was in Lens & Repro the other day (33 W. 17th, in NY) and it looked

like they had two Hypergon lenses with center fans in the case behind

the counter (the fan seemed to be powered by a squeeze bulb and rubber

hose). Don't know what focal length they were, and I understand

they're very expensive, but if you're interested, contact them at

www.lensrepro.com .

lester_moore1 · February 10, 2000

I regularly shoot sand, blue sky, and other subjects that should show fall-off in the corners. With my 90mm f/8 using high contrast Velvia film, there is no noticeable vignetting. With the 75mm the vignetting is VERY noticeable.

patrick_chase · February 10, 2000

Hi Rob;

If it's a 90 f/8 (you didn't specify the F.L.), and you shoot slide

film, and you plan to use substantial movements, then the answer is

probably "yes".

I have a Nikkor SW 90/8, and I found that there was little falloff on

4x5 when the lens was centered w.r.t. the film, but that the falloff

got more dramatic (up to ~1.5 stops) when I used extensive movements.

I ended up getting a Heliopan 1.5-stop center filter to correct the

problem.

I'd like to throw out a couple corrections:

1. It is very important to distinguish falloff from vignetting: They

are completely different animals. Vignetting is what happens when you

exceed the coverage of one of more elements in the lens

(typically the front or rear elements, since they are often a bit

undersized). Vignetting occurs only near the coverage limits, and

typically decreases as you stop the lens down. Wide-angle falloff is

more uniform in character, and is not affected at all by aperture.

2. Bob Salomon writes that "All modern wide angles have similar fall

off". This is decidedly untrue. The exact optical layout of a lens has

a significant effect on falloff. In particular, use of strongly

negative front and rear elements reduces falloff by causing the

entrance and exit pupils to "swing" as the angle of incidence changes.

The catch is that strongly negative front and rear elements tend to

cause aberrations, so the designer must balance sharpness vs. falloff.

Before anybody mentions "cos^4", it should be pointed out that the

cos^4 law only pertains to the idealized thin lenses of optical

theory; Modern wide-angles are anything but "thin lenses"

-- Patrick

bob_salomon3 · February 10, 2000

"2. Bob Salomon writes that "All modern wide angles have similar fall