creative technique obviates expensive center-filter purchase

[squareframe]

I have been using my Schneider 72mm XL Super Angulon on my Linhof Technikardan with great success. I do not use the center-filter as the slight fall-off is not objectionable and is actually a welcomed characteristic in some of my work. my professional colleagues however have been critical of my judgement, and within their own work require it. I had loaned my architectural photographer friend the 72mm XL which promoted lengthy discussions and his insistence that this lens needed the expensive center-filter without question. it was not the expense, but the added workload of removing/attaching the filter and the associated losses that compelled me to look at this problem deeper. I scan all my 4x5 negatives, and simply made an image of a evenly lit white/featureless backdrop. scanning this negative allows me to characterize the lens response and create a Photoshop gradient mask used to normalize the response of the overlayed subject scan.

 

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nothing new here, other than allowing solutions to surface from keeping an open and playful mind. in my case, a good cabernet sauvignon contributed profoundly.

[abiggs]

On a different tangent, do many people feel the need for a center

filter on the Super Angulon XL 90mm? Or just the 'regular' 90mm?

[paul_chaplo]

I strongly recommend the center filter for the 90mm SA XL. (Unless

you have the Cabernet Sauvignon and Photoshop :)) With enough of the

proper vintage, you don't even need film...

[armin_seeholzer1]

Cheers Daniel

 

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I`m working with a Nikon f4,5 75mm and a Schneider SA f8 90mm without

any center-filter and I make some scans and some Ilfochromes and I`m

happy and also my customer.

If I have to shift to the limits of the lens than I use not the full

frame from neg. or I work with hold back under the enlarger or what

ever is needed it depends on neg. or pos. but I never take a center-

filter!

[david_goldfarb]

Yes, it is easy to remove falloff with the center gradient tool in

Photoshop if you're scanning, or by dodging the corners if you are in

the darkroom, but be sure to compensate when exposing to make sure

that you don't lose detail in the corners.

[dan_smith]

Different photographers & clients have different standards and

needs. What may be OK for you might be trashcan material for another

photographer. If you have to go to the trouble to make corrections in

Photoshop, why not do it right from the start? How much trouble is it

to screw on a Center Filter?

It seems you are making extra work for yourself under the guise of

saving time and money. I hope you aren't confusing an "open and

playful mind... a good cabernet sauvignon contributed profoundly"

with getting drunk & not being able to tell a good image from one

that is "good enough".

[squareframe]

the thrust behind my solution is to offer refinement and accuracy to

normalizing the response. obviously, you can create a generic radial

gradient layer that approximates the response that might suffice.

 

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as for Dan Smith's response, his commentary is interesting though I

believe flawed. his belief is that the 'right' way is the existing

way and apparently the only way:

 

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"If you have to go to the trouble to make corrections in

Photoshop, why not do it right from the start? How much trouble is it

to screw on a Center Filter?"

 

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how much trouble is it to avoid the expense of the center-filter,

leverage the light that is not lost to filter attenuation, take

advantage of the decreased setup times allowed by not requiring the

filter? screwing a filter on/off is not necessarily a burden, but

then, neither are two mouse clicks to add the compensation layer.

once again, I am arguing from the Photoshop realm, where we are

scanning directly into our process environment.

 

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I also want to point out that advances in our pursuits can certainly

come from an open and playful mind. we can lock ourselves into

existing ways of thought and convince ourselves that any deviation

must be surely detrimental to our clients cause. this of course is

not true at all.

 

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the point of my comments on having a glass of wine, was only to

represent thinking outside of our self-imposed limitations. Dan, and

others can surely understand that you don't have to add another layer

of glass with its associated problems, to compensate correctly.

understanding math and physics can allow a better and more accurate

solution, cabernet sauvignon influenced or not.

[renee_galang1]

Folks, I have a 47mm F5.6 XL and I wouldn't bother taking photographs

without the filter on, even with B & W! The fall-off is very profound

to say the least. Also, I'm having enough trouble trying to minimise

its distortions.

[squareframe]

> "What may be OK for you might be trashcan material for another

photographer."

 

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and though this might be true, I can easily transpose this and

say "what may be OK for you, based on your old-world and Luddite-

centric view, would be totally unacceptable and below the standards

practiced and demanded by those imploying the refinements and

increased accuracy afforded by the latest technological advancements."

 

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the point is, that we think ... clearly and freely without prejudice

and bias. we express our ideas without self-imposed boundaries or

bullshit ideas of what is 'right' and immutable.

[cesar_barreto]

Maybe it isn't too late to add some comments on center filters.

First, they really become a pain if one needs some other filters,

like usually happens in B&W. But, if contrast control acts in

development, N+1 or above, the fall-of problem certainly gets worse.

And it can be impossible to solve if the subject already shows some

kind of middle hot-spot. Exposure doesn't change while using such

filters, as the borders would be under-exposed anyway.

So, as a conclusion, I'd would never say never about center filters.

They can be quite handy sometimes.

Thanks to all,

 

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Cesar Barreto

[squareframe]

no one is arguing against center filters. they do introduce the

potential contributions of distortion and flare. they also are

expensive, which is hard to justify when the kids want a new 27" Sony

Trinitron and you blow the family savings on a two-inch piece of

glass for the same price. maybe you need the $400 to replace those

old Firestone tires that tend to explode on your Ford Explorer.

 

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or maybe .. you just keep forgetting to put the darn filter on, or

found that you, once again, have left it in your other camera bag. it

happens.

 

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enjoy the moment ...

[erik_ryberg]

Daniel, I tried the cabernet but got a huge loss of film speed, at

least with Tri-x. Maybe I need to play around more with the

dilutions.

[philip_y._graham]

Daniel.

 

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I agree with you that centre filters are a pain. Not only their

expense but something else for me to carry, to get lost or to get

broken. I have also ended up having to buy a separate centre filter

for each of my wide-angle lenses.

 

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Although I can see that it is possible to improve light fall-off by

dodging in the darkroom or using Photoshop on the computer, my query

is whether this is as effective as using a centre filter?

 

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With a wide-angle lens, the light fall-off can be up to 3 stops at

the edge of the image circle which means that if a centre filter is

not used then the edges of the negative or transparency may be

significantly under-exposed assuming the centre is correctly exposed.

As has been mentioned above, this under-exposure will lead to some

loss of detail and clarity and am I not correct in thinking that

although Photoshop can correct the difference in brightness between

the centre and the edge, it cannot restore this lost detail?

 

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It seems to me that if you scanned and manipulated a negative or

transparency that was 2-3 stops under-exposed you might be able to

get a reasonable print but I�m not sure it would be as good as the

print that you would get from a correctly exposed negative or

transparency. In effect isn�t this what you are doing to the edges of

your negative or transparency by not using a centre filter. I suppose

that increasing the initial exposure would help to reduce the under-

exposure at the edges but at the cost of producing some degree of

over-exposure at the centre.

 

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Since I shoot mostly transparency film (as the end product) then

darkroom or computer manipulation has not been of any particular

relevance to me but, time permitting, I have recently decided to

delve into the digital world and so I would be grateful to hear what

you feel of my beginner�s comments.

 

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I like the elegant way you have created a gradient mask

individualised to your 72mm SA XL but I wonder how well this works

when you are using camera movements where the light fall-off problem

on the negative or transparency may become asymmetric.

 

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As to the question above about the 90mm SA XL, I consider that if no

camera movements are being used then the light fall-off is not a big

problem and a centre filter is not always essential. However, with

significant movements I would personally always use a centre filter.

[squareframe]

thank you for your input Philip. the posting was more philosophical

in nature than practical. as you mentioned, there are many instances

where the level of ingenuity does not warrant implementation, as in

asymmetric corrections. as many have noted, center filters are needed

in many critical applications. my point, was rather than craft a

radial gradient scale that only approximates the lens loss in

Photoshop (essentially corner dodging), there were creative (or lame

dependent on your views) and more accurate methods available.

[bob_salomon3]

Cosine failure in wide angles can be controlled without a center

filter

 

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1: have images with naturally darker corners (avoid open sky)

etc.

2: Control the light by overlighting the edges.

3: Dodge and burn the print.

 

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Or to be consistent, since none of the above can be over multiple

prints, use a center filter.

[squareframe]

if I sold center-filters I would surely agree. as a consumer, I

bristle from the fact that my expensive lens purchase requires an

additional expense to use properly. much like buying a car, and

finding out a steering wheel is an expensive option.

[bob_salomon3]

Your lens requires no additiona filter.

 

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The only reason one buys a center filter is because some

photographers do not like the effect of the fall off and don't want

or can't use other means to correct it.

 

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there are many photographers who do not use the filter and, as

you can see by the answers, see no need for the filter.

 

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The only one that determines if the filter is beneficial is you and

your work.

 

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Have you ever called us to discuss the purchase of a wide angle

lens or a camera like a Technorama you would find that we

always reconmmend not buying the filter with the lens and shoot

and see if your your type of work the filter will help.

 

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And yes it would be spiffy neat if we all included the filter when

you buy the lens. But you are right. The fillter isn't inexpensive. It

would make the lenses more expensive.

 

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imagine what people who don't want the filter would say if they

were forced into always buying one.

 

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It's your choice Dan. The physics of the lens dictates the falloff.

 

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THhe photographer has some choices.

 

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1: Buy longer lenses and don't shoot wide angle

2: Live with the fall off

3: Overcome the fall off by control of composition

4: Overcome the fall off by careful lighting

5 Overcome the fall off with corrective burning and dodging and,

if necessary making a copy neg from the corrected print.

6: Buy a filter.

 

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That's the life of a photographer.

 

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You also can to some extent control how much you have to pay

for the fitter

 

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You can use Schneider, Rodenstock or heliopan center filetrs

(except for some extreme wide lenses from 35 to 47 where the

manufacturers filter works best to avoid mechanical vignetting).

[squareframe]

Bob, you have turned my posting on its head. I do not use the filter,

and as my post states, I do not desire a filter as I use the fall off

to underscore the true distribution of light from my lens. I also

recognize that not everyone has this same relationship and may want

to add corrections. post-exposure, my idea works well, though not

necessarily offering grand improvements over simple dodging.

 

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you do not have to remind us that we have choices as a photographer.

I embrace that with a passion, which is the essence of this post. my

choice? to think smart, explore ideas, keep an open mind, and have a

wonderful time along the journey.

[sid_crandall]

You have to also consider the cost factor of the 4x5" size (or other)

digital film scanner to achieve a file for your computer. I have

never sceen a large format scanner for the cost of a center gradient

filter.

The additonal cost for digital bureau scanning could quickly add up

to the cost of the center filter.

The inconvienince of dealing with these digital bureau persons and

the time it take to get to them also has to be a factor.

After being forced into digital by the market, my heart is begging

for the good old days of doing it right the first time!

My two cents worth!

[squareframe]

good point sid. of course, if you own several lenses and require

center filter for all of them, it quickly adds up. I work almost

exclusively with B&W and use a $400 Epson 1640 to scan my 6x6 and 4x5

negatives. the correction layer is a mouse click away, so the time

investment is essentially zero. this assumes you are already

including scanning into Photoshop as part of your workflow.

 

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I guess the bottom line, is that if the technology you embrace does

not help you meet your goals, does not stretch you closer to your

true vision, save you money and energies, or whatever your objectives

are, then you should reconsider this choice of direction.

 

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the center-filter idea is to throw away light in the best part of the

lens, to better equalize the response from center to edge. why is

this the 'right way', when in many instances it is simply an

unnecessary waste of precious light?

 

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we've beaten this up pretty good. I suspect we could all use a fine

glass of cabernet and let the ideas flow.