4x5 wide angle lens primer?

[MIke Sherck]

I've always been a longer-than-normal lens sort of guy but lately I've gotten an itch to try shorter focal lengths. I'm currently making a wide-angle bellows for my old Zone VI 4x5 and am interested in lenses from 90mm and shorter, particularly in the 75mm range. Would a 75mm lens for 4x5 need a center filter? At what point would a wide lens for 4x5 need one? Finally, while I don't find f/8 or f/9 to be an issue with 300mm, 355mm and 420mm lenses on 4x5 or 8x10, I understand that the effects of small apertures are more pronounced at shorter focal lengths (dimmer image on the ground glass.) Do you find 90mm f/8 to be unworkable? How about 75mm f/8?

Thanks!

Mike

[Jack Dahlgren]

Use of a center filter depends on your tolerance for light fall-off and how close you are the the edge of the center filter. I use 90mm without a center filter but I'm usually outside and a perfectly even illumination is not that important to me.

The wider the lens the worse the fall-off becomes.

It all depends what you consider tolerable and the trade-offs you are willing to make.

f/8 is workable. But larger apertures help with finding focus. Wide angles are harder to focus because DOF is larger so f/5.6 or f/4 will help narrow down your point of focus.
Also helpful indoors or dim conditions.

If f/8 were unworkable then they wouldn't sell very well would they?

I don't have anything shorter than 90mm so I can't comment on 75mm.

[bobwysiwyg]

A question from one who is technically impaired. What is a center filter?

[Eric Woodbury]

Bob, In most lenses, light falls off, decreases from center, at a rate of "cosine to the fourth". This is minor until you get into wide angle lenses and then it creates the appearance of a bright center and dark perimeter. With some subjects and in BW, this can be hidden or made non-distracting, but if you want it even, then you use a center filter that is the opposite of fading off at the edge, it is darker in the center and becomes more transparent at the edges. This counteracts the falloff, but costs you a couple of stops in lens speed and several hundred dollars. And different lenses use different filters ... sometimes. Keep the wallet open.

[dave_whatever]

Generally people tend not to use CFs on 90mm on 4x5, I think they really start to be used from 65mm downwards, but it will all depend on what you're shooting. Falloff is more visible in areas of even tone like clear skies. I had a 65mm f/8 and in general landscape use (i.e. stopped well down) the falloff wasn't a problem - you could actually use it to your favour in some cases. I did try to avoid using it against a clear sky though. The other thing to consider is if you're scanning then its pretty trivial to correct in photoshop if you have no choice.

The f/8 issue can depend a lot on your ground glass, fresnel and length of lens. I dare say an f/8 lens on a snazzy bright ground glass can look brighter than an f/5.6 lens on a dull old glass. For me using a fresnel was like night and day on a 65mm lens.

A 90mm f/8 is a lot brighter on the glass than a 65mm f/8, and a lot easier to compose with because there's less falloff and falloff is always more severe when the lens is wide open for focussing.

Another thing to consider is the wider you go the less you have to tilt, to get front-to-back focus for example. This means it can be quite hard to do prescisely on a camera without geared tilt because even the slightest slip or if you don't tighten a knob fully it can throw the focus. And also means if you knock anything out of a zero position when the camera is in transit even a tiny amount which you don't notice it can give you problems.

If you're new to wideangles the most obvious thing to suggest is not to go too balls-deep at first, go with a 90 or 110mm to start with, it may end up being all you ever need.

[domaz]

If you are doing the digital workflow then compensating for the lack of a center filter should be possible. I remember seeing an older C program that could do it- there may be more modern Photoshop plug-ins and such by now. Center filters aren't cheap so it's a good thing to investigate and save a little money.

[Joshua Dunn]

Mike,

I use center filters on 90mm and below but I am a techno-tard. A lot of this is a matter of taste but to me light fall of is not just a lack of exposure but a loss of information. This will be exaggerated with any movements you use. Like a lot of things you just need to try it and see how you feel about it. If you don’t know someone who has a 75mmish lens with a center filter than maybe rent one. The ideal trial would be for you to photograph a subject that is typical of what you plan to shoot with a wide lens on 4x5 with and without a center filter and see what you think.

-Joshua

[bobwysiwyg]

Bob, In most lenses, light falls off, decreases from center, at a rate of "cosine to the fourth". This is minor until you get into wide angle lenses and then it creates the appearance of a bright center and dark perimeter. With some subjects and in BW, this can be hidden or made non-distracting, but if you want it even, then you use a center filter that is the opposite of fading off at the edge, it is darker in the center and becomes more transparent at the edges. This counteracts the falloff, but costs you a couple of stops in lens speed and several hundred dollars. And different lenses use different filters ... sometimes. Keep the wallet open.

Eric,

Thanks for the very clear explanation, very appreciated.

[MIke Sherck]

I see some background would have been helpful. Sorry for missing that!

My widest lens to date is my Fuji 125mm; before that, it was an Ektar 127mm. I tried someone else's 90mm Angulon once and the camera barely came to infinity focus with the regular bellows, so that's why I'm making the wide angle bellows. To date I don't do digital. Most of my photography is B&W and I print in my darkroom but my local color lab no longer makes wet color prints from 4x5 and I'm more than a little unhappy about having to pay $25 for a scan for each negative, plus then a print. We'll see what happens next with color, but that's not really part of the wide-angle experiment.

Maybe I should look for an old 90mm Angulon or something similarly inexpensive, just to see the difference from my 125mm? Or would that be too close to make much difference? Then, there's a 75mm f/8 Super Angulon on Ebay which might end up affordable... I know that the Angulon won't give me much in the way of movements but generations before me have lived with that and I probably can, too.

Mike

[Thebes]

FWIW, I have a 90mm f8 Super Angulon... an older one which are cheap at Keh. I used to own a 90mm Caltar f6.8 (relabeled Grandagon). I DO find the SA f8 to be considerably more difficult to focus. If I were buying again I would definitely buy the Gradagon instead, or the Caltar version of it which I am sure is just as good. I will probably sell my 90 SA and buy a faster 90 at some point in the future... shows how saving a bit can be more expensive in the long run.

I've never used a center filter with a 90mm. I suppose I might for transparency film or architecture which I don't shoot enough to worry about.