Center Filter Requirements

[michael_kadillak3]

Why do certain Rodenstock and Schneider wide angle lenses require center filters whereas Nikon lenses do not? Is it a design issue specific with the manufacturer or should you use a center filter with all wide angle lenses. I have several Nikon super wide angle lenses (120 and 150SW) and have not noticed fall off problems, although I only shoot B&W. Thanks

[jorge_gasteazoro]

Michael, I have wondered the same for a long time, I have a 65 mm for

my 4x5 and I have never seen fall off, like you I only shoot B&W but

I used it once to take a city scape with fuji velvia and the results

were beautiful, no light fall off at all. Since this lens barely

covers 4x5 I imagined I would have seen the fall off easily.

 

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In a previous thread I comented on this that nikkors do not seem to

need this center filter and some smart ass answered "physics do not

change, designs are all the same" I decided not to argue with this

guys since obviously he has not used the nikkors and was obviously

unaware that designs are not "all" the same. In any case I guess I am

not answering your question, but I concurr with you. Hopefully

someone more knowledgeable than me will enlighten us.

[paul_owen]

Just a thought, but your 65mm may show fall-off only when you apply

movements to the camera. Lens specs, especially from Schneider, tend

to underestimate the covering power of their lenses by a fair

margin. Your lens may just about cover the 5x4 format as long as you

do not apply movements. Also, vignetting will be more noticeable on

expanses of blue sky than other subjects. As I said, just some

thoughts!! Regards Paul

[don_welch]

I spent 30 minutes looking for any obvious explanation on the

internet. I found reviews for 65mm and 75mm Nikkors in which the

users commented on obvious falloff, but which they reasoned was to be

expected with any wide angle lenses. I know this goes against

Jorge's experience with the 65mm lens. I think that Michael might

not notice it with his 120 and 150 lenses because of the greater

coverage and the fact that falloff is greater with shorter focal

length wide angle lenses. I use a 90mm Schneider, and falloff is not

a big problem unless I'm pushing the coverage of the lens, and

especially when the subject is evenly lit.

 

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I think that Nikon lenses probably need the filters as much as lenses

made by other manufacturers do, but the confusion arises from the

fact that Nikon does not choose to make Nikon brand center filters

available. However, since filters made by Hoya and others will fit

the Nikon lenses, this is not a problem. I couldn't find anything to

support Nikon lenses being magically less susceptible to falloff, but

it is an interesting question that has crossed my mind before.

[eric_boutilier_brown2]

I have just bought a Nikkor-SW 150mm lens, and have noticed the lack

of fall off - several times I have used it right to the edge of the

image circle, and it just dies, over 1/4" or so, with almost no

darkening before the severe drop-off.

 

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Why? I suspect it has to be because of the lens design; when you stop

the lens down (to say f/22) and look at the lens opening on an axis,

it visually looks like a proper circle, not an elongated oval, like

some other lenses. I suspect this is why the fall-off is limited; the

lens is designed so the aperture looks like a proper circle form any

angle.

[jorge_gasteazoro]

Paul:

 

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I agree with you, but with the 65 mm mounted on a 4x5 you only have

about 10 mm movement before you loose coverage, of course this is

wide open, I imagine I have a little bit more when I stop down, but

nevetheless I am unable to see light fall off. I have used this lens

with the minimal movements I can get and still I am unable to see

this problem.

 

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Don:

 

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I thought the same thing, since Nikon never mention this I thought

they were operating under the phylosophy of "is easy to ignore a

problem if you don't know one exists" :-)))

But then before I bought my lens I asked the Nikon rep in Houston to

let me borrow her lens because she had told me they did not need a

center filter as the Schniders do. As I put it to the test I was

never able to notice a problem. Again maybe is because I only shoot

B&W and the one color slide I shot was without movements, but still,

with such a border line coverage I was sure to see the light fall off.

I don't know maybe I got lucky and got the one magical lens..lol.

[rich_silha]

the nikon lens tech i taked to stated that all thier sw lense designs

compensate for "wide angle fall off" elliminating the need for using a center filter.

i've been using my nikor 90sw f4.5 on

my 6x17 and a nikor 150sw f8 on 8x10 without any falloff problem.

[kerry_thalmann2]

Jorge,

 

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If you are referring to the thread titled:

 

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CF for Nikon 65mm/4.0 - comments please?

 

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http://hv.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=005vBH

 

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Then I appear to be the so-called "smart ass" who refuses to ignore the laws of physics WRT to light fall-off with wide angle lenses - regardless of brand name. Sensitivity to fall-off is extremely subjective. It varies greatly from person to person, but is also a function of the materials, subject and lighting. In my reply in the previous thread, I was not trying to be a "smart ass", just sharing my experience. Just because my experience, needs and opinions differ from yours does not make you right and me wrong, or vice versa. This is a subjective matter where people of differing needs can, and do, come to differing conclusions. You may not agree with what I say, but that alone does not make me a "smart ass" for stating my opinion and sharing my experience.

 

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That said, I admit that I have no experience with the 65mm f4 Nikkor SW. However, I have used the 75mm f4.5 Nikkor SW extensively, and for MY NEEDS, I found a center filter absolutely necessary. Both lenses are of the same design, and since fall-off is a function of angle, the 65mm should be even worse in this respect than the 75mm of like design.

 

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Fall-off will be much more noticeable with high contrast color transparency films than black and white films or even color print films. Since I shoot 100% with color transparency films these days, I find a center filter necessary for MY needs with the 75mm Nikkor SW. You shoot black and white and do not find a center filter necessary for YOUR needs with your 65mm Nikkor SW.

 

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Different users + different needs = different conclusions. No surprise there. If you go back and re-read the previous thread in question, you will see that other posters who have actual experience with the 65mm Nikkor SW find the center filter necessary for THEIR needs. Again, different users with different needs. You will probably see the same thing in this thread - some will state that they find a center filter necessary with the Nikkor lenses, you will say that they do not. This is obviously an area where reasonable minds can disagree (without resorting to name calling over a difference of opinion). The only real way any particular user can decide if the center filter is necessary is to shoot some test shots with their lens, their materials and their subjects and examine the results with their eyes and decide if they find the fall-off objectionable. Once they have done this, it matters not what you, I or the laws of physics say. They will have the answer that best suits their needs. There is no magic involved, just a simple test.

 

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BTW, I'm not knocking the Nikkor SW wide angles here. In fact, I think they are fantasic. IMHO, they offer outstanding sharpness and great coverage combined with relatively compact size and light weight. All things I consider highly desirable in any lens.

 

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Kerry

[kerry_thalmann2]

Oops, typo in my previous reply.

 

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I wrote:

 

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"You will probably see the same thing in this thread - some will state that they find a center filter necessary with the Nikkor lenses, you will say that they do not."

 

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What I meant was:

 

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You will probably see the same thing in this thread - some will state that they find a center filter necessary with the Nikkor lenses, others will say that they do not.

 

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Kerry

[jorge_gasteazoro]

Kerry:

 

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I dont know if it was you or not, in any case you are a frequent

poster in this board and always very helpfull, if this is the case

and it was you then I apologize for the characterization, I did not

mean to offend you.

BUT, I agree with you that sensitivity might come in play, on the

other hand when you use a densitometer to measur side to side density

and it only varies by .05 then I think I am ruling this out.

I took a pic of a gray wall with the lens defocused and after

developemtn in JOBO expert drums I took the densities....so, I dont

know, maybe like I said before I got a magical lens....:-))

[kerry_thalmann2]

Jorge,

 

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Apology accepted (but not really necessary - you'd have to try a lot harder than that to REALLY offend me).

 

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Not sure what you mean by "defocused" in this context. Just keep in mind that the fall-off will be worst with the lens focused at infinity. The size of the image circle increases as you focus closer (increase extension). At 1:1 (extension = 2x focal length), the image circle will be twice as large as it will be when focused at infinity. So, if the wall was closer than infinity (or, more accurately, your extension was greater than required for infinity focus), you will not see the worst case fall-off. This is one possible explanation for your test results.

 

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When I shoot landscapes (approaching infinity) on color transparency film with the 75mm Nikkor SW, there is definite fall-off in the corners. It is especially obvious when there is a bright blue, even toned sky. The fall-off from center to edge is on the order of 1.5 - 2 stops. That is why I find a center filter necessary with this lens.

 

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FWIW, I have yet to find any lens under 90mm (on 4x5) that did not require a center filter for MY needs. That includes the 75mm f4.5 Nikkor SW, 75mm f6.8 Grandagon-N, 65mm f5.6 Super Angulon and 80mm f4.5 Super Symmar XL.

 

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Again, there is no "correct" answer to this question. The answer will depend on the user and the application. FWIW, I truly do wish I didn't require a center filter on my wide angle lenses. They are a pain - expensive, you lose 1 1/2 stops, and it makes it a pain to use other filters. If you find them unnecessary, count your blessings.

 

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Kerry

[micah_marty1]

"I have several Nikon super wide angle lenses (120 and 150SW) and

have not noticed fall off problems, although I only shoot B&W."

 

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Michael, I don't know which formats you're shooting, but with color

you'd probably notice more light falloff. I think it's quite

noticeable--if not objectionable--in Provia shot with the 120SW on

8x10 and also with some RTP I shot with the 150SW on 11x14. These two

lenses just barely cover these two formats, so even if I wanted to

use a center filter (and even if I could afford the 95mm CF for the

150!) I probably wouldn't choose to use it because it would

definitely vignette, no matter how thin the filter.

[walter_glover]

Michael, Kerry, Jorge, at al.,

 

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I have referred back to the earlier post on this topic and feel that I

may also have been in the running for the erudite donkey epithet,

along with Kerry.

 

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I would point out, however, that in their literature Rodenstock

state " ... largely compensates light fall-off towards the edges by

an optical trick (making use of pupillary distortion) ... " with regard

to the Grandagon-N range.

 

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In other words, the apparent size of the aperture is optically

distorted towards the periphery of the image circle to lessen

fall-off. No claim is made that it eradicates fall-off completely

and, in fact, it is suggested that a centre-grad be used for

optimal rendition.

 

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Clearly Nikkor lenses display this same property, even if it is not

stated in their literature, and as noted by Jorge this results in a

less eliptical aperture when viewed obliquely.

 

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That said, and in agreement with the earlier posts, it is down to

personal perception and interpretation of a motif as to whether or

not application of a CF is desirable. The Centre-Grad is another

tool in our vast asenal along with polarisers, contrast filters,

expanded or contracted development and every other

manipulation known to us to assist in making a visual

statement. If you want to use it, use it ... if you don't, then don't.

But please, let's be concilliatory and avoid the temptation to

transform it into a catalyst for paroxysm.

 

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Cheers ... WG

[jorge_gasteazoro]

Kerry, exactly....I thought if the fall off is worst at infinity...in

this case focusing distance of 65mm, then if I focus at infinity and

place the wall 6 feet from the camera then there would not be any

sharp image and all I get would be light transmission. Am I mistaken

thinking this way? This method has worked very good for me to test

development since all I get is an uniform negative....this way I can

see development problems, uniformity in development and yes...light

fall off....

[ellis_vener_photography]

Uh, guys, if you look atthe specs Nikon uses a different lens

formula from the one Rodenstock uses for the Grandagon

series and Schneider uses for the Super Angulon lenses. if you

do test and find you need a center weighted filter, might I be so

bold as to suggest the Heliopan 0.45ND CWF filters?

[ellis_vener_photography]

Uh, guys, if you look at the specs Nikon uses a different lens

formula from the one Rodenstock uses for the Grandagon

series and Schneider uses for the Super Angulon lenses. if you

do test and find you need a center weighted filter, might I be so

bold as to suggest the Heliopan 0.45ND CWF filters?

[michael_kadillak3]

Thanks for the great contributions to all. I use the Nikon 120 SW for

5x7 and the Nikon 150 SW for 8x10 so I have plenty of coverage. As a

result, I have not had to deal with the expense of a center filter

(these must be very difficult to produce because they are big $$)for

B&W and the extra exposure requirements.

 

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I was contemplating a 75mm or 65mm for 4x5, but may just stay with my

Nikon 90mm f8.

[kerry_thalmann2]

Ellis,

 

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It doesn't matter if the Nikkor design is different than the Schnedier, Rodenstock, Fuji or Zeiss Biogon type from which they are all derived. It still must obey the laws of physics. The fall-off characteristics cannot be better that the theoretical limit for an ideal lens. This is simple geometry at work here. Of course, having said that, I admit my memory is a tad fuzzy (it's been decades since I had a physics class that dealt with optics) and I have no text handy. So, from memory (not that I need to encourage it, but everyone please feel free to correct me if I'm wrong)...

 

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The theoretic, best case fall-off for a lens with an entrance pupil that appears elliptical off-axis is a function of cos^4. For a design that uses a so-called tilting entrance pupil, the theoretic limit becomes a function of cos^3. I believe all modern Biogon derived large format wide angles are of tilting entrance pupil design. Other than a center filter (or similar trick), I know of no way to improve upon this theoretic minimum for light fall-off in lenses designed to be relatively free of distortion. Of course, a fish-eye lens will not have this cos^3 fall-off, but suffers from severe distortion (no free lunch). Based on real life use, and looking at the MTF curves (for Schneider and Rodenstock), it would appear that modern large format wide angles from all four major manufacturers come close to, but do not beat this cos^3 best case limit (for subjects at infinity).

 

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Now we're arguing physics and not photography. I still say the best way to find out if you need a center filter is to run some tests without one. If you don't find the fall-off obectionable for your materials, subjects and application - screw the theory and skip the center filter. Some people will absolutely claim they NEED a center filter on a 90mm for 4x5, others will say they shoot with a 55mm (also on 4x5) and say they've never felt the need for one. To each his own. My personal "limit" seems to be anything less than 90mm on 4x5. But, again, that is based on what and how I shoot and what my eyes see in the results. YMMV!

 

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Kerry

[kerry_thalmann2]

Michael,

 

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Given the fact that you don't find a center filter necessary for your 150mm SW on 8x10, you would probably not find one necessary using the 75mm SW on 4x5 (assuming the same materials). After all, theta stays the same in these two cases. You've just cut the two sides (focal length and distance to the corner of the film) of the triangle in half. Similar triangles with identical angles.

 

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Kerry

[william_marderness1]

I have used a Nikkor 90SW and a 120SW for 4x5. With color print film,

the fall off with the 90SW was objectionable. Even the fall off of the

120SW with rise bothered me.

[nick_jones]

Michael's original question concerned Rodenstock and Schneider WA's,

which he says require CF's, in comparison with the Nikkors, which he

says do not. However, most of the ensuing discussion has concerned

only the Nikkors and from it, where my own needs and interests are

concerned, I've concluded that I could probably use the 150SW on 8x10

to shoot b&w without worrying too much about fall-off, although I'm

still very unclear whether or not this has anything to do with some

peculiar design feature of the Nikkor.

 

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But what about Rodenstock and esp. the Schneider super symmar 150XL

under similar conditions? Has anyone used the 150XL with b&w on

8x10? As Kerry puts it, the best way to find out if you need a CF is

to use the lens without one. Some help here would be valuable, since

the B+W 4a CF for this lens is so expensive as to wipe out any price

differential vs. the Nikkor 150SW (at this point, I'm uninformed on

alternatives to the B+W). Any informed input would be most

appreciated. Nick.

[michael_briggs2]

Re: "...although I'm still very unclear whether or not this has

anything to do with some peculiar design feature of the Nikkor." of

the last response. As far as can be determined from the published

literature, the non-aspheric very-wide coverage lenses of all four

manufacturers use the same optical trick of tilting the pupil to

reduce the light falloff. Confusion seems to result because the

German manufacturers market center filters and publish data on the

illumination falloff, while the Japenese do not. The designs in this

class are the Fuji SW, Nikkor-SW, Rodenstock Grandagon (including Apo)

and Schneider Super-Angulon (including XL, but not including the plain

Angulon). These lenses have falloff going as approximately (cos

theta) cubed. While the optical theory says that the illumination

goes to the third power, when I analyze the published data, I

generally find that the illumination falls off somewhere between the

third and fourth power, i.e., a little worse than theory, but still

better than a lens that doesn't use the tilting pupil trick.

As far as I can tell from the published information, there is no

reason based upon illumination falloff to pick one of these lenses

over another. Even though the illumination falloff is improved, it

still exists and some people for some uses may find a center filter

useful for any of these lenses.

 

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The Super-Symmar XL series are super-wide coverage lenses using

aspheric technology. From the illumination graphs that Schneider has

published, they do NOT use the optical trick to reduce the falloff of

illumination. The published curves follow the (cos theta) to the

power of four law quite well. Therefore illumination falloff may give

a potential buyer a reason to select a different super-wide coverage

lens. On the other hand, these lenses are small, light-weight and

fast, and these characteristics will be more important for some users.

One could always use a center filter with one of these lenses to

improve the uniformity of the illumination of the film.

 

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The curves that I just analyzed for this response are those of the 150

mm Super-Symmar XL at

<http://www.schneideroptics.com/large/datasheets/ssymxl/ssymxl5,6-150/ssmxl5,6-150p1.htm>

and the 165 mm Super-Angulon at

<http://www.schneideroptics.com/large/super_angulon/daten.html>.