Cut Corner check for vignette on 90mm Nikkor

[tom_may]

Just got a new lens, shortest in my bag: Nikon 90mm f/8 (for 4x5).

When I look through the ground glass cut corners - focused at

anything reasonable for landscape work - I see the dreaded football

at any aperture greater than f/16.

 

Not that I'll often (if ever) use the lens wide open, but if I want

to is it going to vignette? Funny thing is that the corners of the

glass look fine, doesn't seem to be any fall off, though I know

better than to think that means all that much. However, the image

circle should be more than enough to fully cover; it has a 235mm

image circle at f/22 - does it drop off that much open one or two

stops?

 

I know, I know: "try some film" - I will but I just hate to waste too

much money and effort right now, and knowing the vast knowledge of

our wise and experienced community I thought I'd get some advice.

Incidentally, This is one of the few times I couldn't find the answer

to my exact question in the archives, man we have a great knowledge

base in PN, don't we?

 

Thanks in advance for your kind attention.

[photodon]

Tom

 

If is isn't a wide or SW then it might not be a 4X5 lens.

do you know for sure that it is for 4X5 amd not 21/4 X 31/4?????

 

Try a Polaroid for a quick check

 

www.docameron.com

[eugene_singer]

Tom, you should check for vignetting after you close down to the final aperature, just before you are ready to fire the shutter. Do you plan on shooting at aperatures wider open than f16? I used the Nikon 90 f8 SW lens for many years. It only vignetted when I attempted to use too much front rise. I usually used at a smaller aperature than f16 (f22, or f32). Are you using a lens hood? A hood that is under sized will often cause vignetting when using it with a wide angle lens. It's a great lens. One of the best of the f8 90mm wide angles available.

[ellis_vener_photography]

If you can see light coming through the corners even if it is football shaped, you are okay. What you don't want to see is nothing: that is vignetting. As you point outThe 90mm SW Nikkors , both the f/8 and the f/4.5 have very ample image circles even for 5x7 use, but perform best at apertures from f/16 to f/32.

[dave schlick]

the lens specs are 235 at f22, if yoou open the lens yo have less coverage on the film.. you may have put a filter on, this costs you coverage.. as the light goes thru the lens it reverses, that is you see the oposite side of the lens,, the corner you are looking from will show the lens edge or filter if apeture is too wide(open) for tthat rise,fall etc. get a 10 power loop and coat or hood, and check the corners at the apeture you are shooting at after focus etc.. you will see more football shape at wide open, but stoppd down too shooting apeture it will be ok sometimes.. if apeture is not round at apeture setting yo will shoot at you will have vigyetting.. good luck dave, ffffg

[gary_frost1]

Nikon also specs the image circle for this lens at f/8 to be 154mm.

Almost covering 4X5, this seems just a bit optimistic to me.

Mine is looking good for 4X5 coverage by f/11. I doubt you would

notice the falloff (beyond cosine sq) by f/11 with this lens. Hey, try it at f/8 to see what you get.

[jason_greenberg_motamedi]

Tom, I get the same football shape with my Nikkor. Basically, all it is telling you is that unless you stop down past f/16, so you can see all sides of the aperture, you will not have an equal amount of light falling on the corners as on the middle. This may or may not be noticeable on film. It is usually considered standard practice to make sure that you can see all sides of the aperture, however if you will be working with large apertures this will be pretty much impossible to do. I am sure that someone will correct me (please do!) with the correct cosine, or some such, but I usually function by imagining that the percentage of the aperture which is obscured is the percentage of light I will lose.

[bob_salomon]

1: are you using a fresnel to view or just a gg?

2: are you using a center filter to correct for the fall off?

[tom_may]

Folks,

 

Sorry I left out several important parts. To answer your questions: yes it is the SW (as some of you figured out, because of the coverage), I'm viewing on gg without fresnel, and I'm talking about use of it without hood, filter or camera movements.

 

Gary, intersting that the coverage at f/8 is 154mm - I hadn't seen that. Jason, intersting thought about percentage of light lost. What you're saying is that the light falloff will be equal to the aperature covered. Eugene, I've heard that it's a wonderful lens which is why I bought it, I'm looking forward to using it (if the wind will ever die down).

 

Looks like what you guys are telling me is that there will indeed be some falloff at large aperature (probably not right to call it vignetting, just falloff, right?). Again, I don't know that I'll ever shoot wide open, but I'll have to try it just for goofs.

 

Thanks to all for the info, and to anyone else that has something to add.

[mark_sampson]

I use this lens, and have never seen vignetting. And I've had full-frame pictures published that were shot at f/8 (ran out of strobe power). It's a great lens.

[butch_welch]

When Nikon lists the coverage wide open or stopped down to a certain aperture they are talking about the circle of sharp focus, not the circle of illumination. The circle of illumination is the same wide open as it is stopped down, it doesn't change.

[bob_salomon]

"Looks like what you guys are telling me is that there will indeed be some

falloff at large aperature"

 

No there will be fall off at all apertures. That is why wide angle lenses are

commonly used with a center filter.

[d._kevin_gibson]

Not many people bother with centre filters on 90mm lenses though - fall off is negligable with something like the Nikkor 90mm f8. If it is noticable (in skies and such) it's not unpleasant, compared with what you will find with wider lenses - 75,65 and so on (on 4x5)