Vignetting question

jgoody · Jul 23, 2017

I have purchased two sizes of lens shade to use with a new to me old lens. I would like to use the smaller diameter hood if it doesn't vignette. I was planning on doing a few test shots with each hood to check for vignetting. Does the f stop matter? Is the hood more likely to vignette if the lens is wide open?

macfred · Jul 23, 2017

You have to close your aperture to see vignetting.

markbarendt · Jul 23, 2017

Yes aperture matters.

Sirius Glass · Jul 23, 2017

Open the back of the camera and look through the lens with the lens hood on. You can do a quick test to see if there is any vignetting at different apertures without wasting film for the first series of tests.

jgoody · Jul 24, 2017

Sirius Glass said:
Open the back of the camera and look through the lens with the lens hood on. You can do a quick test to see if there is any vignetting at different apertures without wasting film for the first series of tests.

Don't I need a ground glass for that - or can I see vignetting without one?

Andrew O'Neill · Jul 24, 2017

What camera are you using?

jgoody · Jul 24, 2017

Canon P and Canon 7 cameras - the lens is a Nikkor 5cm f2 LTM - the lens hoods are old Kodak series 6 with an adapter. One hood is quite flared and I am confident will be ok; the other is narrower, and preferable if it doesn't vignette.

Andrew O'Neill · Jul 24, 2017

Looking through the back, from the corners, to see if you can see the lens hood. If you can, chances are it'll vignette.

Europan · Jul 24, 2017

Frosted self-adhesive tape makes for a quick GG.

Sirius Glass · Jul 24, 2017

Sirius Glass said:
Open the back of the camera and look through the lens with the lens hood on. You can do a quick test to see if there is any vignetting at different apertures without wasting film for the first series of tests.

jgoody said:
Don't I need a ground glass for that - or can I see vignetting without one?

No, you will see the blockage when the lens is fully open.

jgoody · Jul 25, 2017

No really sure if I am seeing blockage or not looking through the back of the camera but something else occurred to me. The horizontal FOV of the 50mm lens is approx 40 degrees. It would seem that if I projected two lines at a 40 degree angle intersecting at the "optical center" (if that's the right word) of the lens I could see on paper if they intersected the sides of various lens hoods. Perhaps the place where the lines intersect is where the iris is -- I don't know? Am I barking up the wrong tree here??

macfred · Jul 26, 2017

Come on, jgoody - close your lens and ...

jgoody said:
I was planning on doing a few test shots with each hood to check for vignetting...

It's not all that difficult

Hikari · Aug 5, 2017

A simple visual inspection with the aperture wide open should tell you. As suggested above, simply look from the film plane at the corners to see if the hood can be seen.

markbarendt · Aug 5, 2017

Hikari said:
A simple visual inspection with the aperture wide open should tell you. As suggested above, simply look from the film plane at the corners to see if the hood can be seen.

That view depends on the image circle size, which is not the same as the film size.

Huub · Aug 7, 2017

Open back and shutter and then look from the frontt the lens with the hood on. If you can see all 4 corners of the image frame glancing just past the hood, it will have no vignetting. If you can't see all 4 the corners, it will vignet. That is how i check it using a 4x5 view camera and it should work on 35mm and 120 too.

Closing the aperture isn't important. You should be able to shoot wide open without vignetting too. And then: image circle isn't an issue on 35mm anyway, except when using shift and tilt lenses.

markbarendt · Aug 7, 2017

Not necessarily. The classic picture of a single ray of light moving through the lens doesn't tell the whole story. Similarly looking through the lens doesn't follow a single path.

When light bounces off a single point in the scene back toward the lens that light metaphorically follows millions upon millions of paths that are spread across the entire face of the lens and those millions of paths pass through the glass separately and those millions of paths emerge separately but are aimed/focused toward a single point on the film.

Vinetting happens when metaphorically a few hundred thousand of those paths are blocked by something (like a hood) that causes a darkening in the corners. It's not a blockage where you simply can't see the subject you are looking for, it is simply a limit on total exposure for that specific subject/point on film pairing.

jgoody · Aug 7, 2017

Wow, who knew this was so complicated! I did some tests and as soon as I finish off the roll I'll report back. I used the wider hood, narrower hood, a 40.5mm to series 6 adapter (like a mini hood), and nothing.

markbarendt · Aug 7, 2017

Giggle, yes photography is really complicated if you think about everything that has to happen. It's nice that we don't have to think about all those things to make every photo.

So, on your tests were you at full open aperture? If you were stopped down you changed the vignetting characteristics.

jgoody · Aug 7, 2017

I believe I stopped down as it was suggested that would show vignetting better. Oh for the simple life with the factory correct lens hood!

markbarendt · Aug 7, 2017

We are reaching the limits of my understandings here but I'll use what I have been able to dig up about my Mama 150SF lens for my RB67. SF stands for Soft Focus.

Wide open the image that reaches the film includes light gathered from the glass all the way to the edges (so to speak).

The 150SF lens is purposely designed with aberrations in the areas further from the central axis to make the soft focus effect. As the lens is stopped down the aperture blocks the light paths from the glass areas furthest off center. Once the adjustable aperture blades reach the f/8 setting or anything smaller the lens simply behaves as any normal lens would because only the central glass areas closer to the axis that were designed to be without aberrations are transmitting light from scene to film.

In short: as aperture becomes smaller, less and less of the front glass is being used to transmit the image to the film.

To allow some effect at apertures smaller apertures than f/4 Mamiya provided special disks with these lenses to use instead of the adjustable aperture blades in the shutter. These disks have small holes outside the central aperture hole that allowed some of the lens aberrations to reach the film.

This concept is seen in other places too. Large format photography, a Petzval lenses' swirly goodness comes from aberrations outside the central area of the lens. Many of those lenses were originally designed as projector lenses where only the central area of the lens was ever intended for use.

As counter intuitive as it may seem these lens aberrations were once a very important part of professional photography.

Many, many, many years ago as photography moved from slightly fuzzy images to really sharp images, making portraits of middle aged women of means (who were as they are today, the people who pay for photos) ran into a huge problem; wrinkles. Being more than a full century before the advent of PhotoShop posed a serious threat to the photographic portrait business. Soft focus lens were one of the ways photographers overcame that problem.

blockend · Aug 9, 2017

My old XA2 used to vignette like a silent movie and had no hood whatsoever, weirdly I've just purchased another. On the other hand I use a 50mm hood on 28mm lens (42mm on my APS-C DSLR), and it doesn't darken a jot at any aperture. The only way is to try it and see what happens, but don't confuse optical vignetting which many older and some newer lenses suffer from, with cut off from the hood.

RalphLambrecht · Aug 9, 2017

Sirius Glass said:
Open the back of the camera and look through the lens with the lens hood on. You can do a quick test to see if there is any vignetting at different apertures without wasting film for the first series of tests.

+1

E. von Hoegh · Aug 10, 2017

jgoody said:
Wow, who knew this was so complicated! I did some tests and as soon as I finish off the roll I'll report back. I used the wider hood, narrower hood, a 40.5mm to series 6 adapter (like a mini hood), and nothing.

It isn't complicated, it's merely made to seem so.

Put a the shade on the lens, maximum aperture, focus at infinity. Set camera on tripod, back open/off, shutter open. Look from each corner of the film gate through the lens, if you do not see the lens shade, you do not have vignetting. For instance, look from the lower left corner of the film gate, aligning your eye with a line extending from the lower left corner of the gate to the upper right segment of the lens aperture, do this for all four corners - lower right gate, upper left lens aperture, etc. Simple as dirt.

removed account4 · Aug 10, 2017

Europan said:
Frosted self-adhesive tape makes for a quick GG.

waxed paper too ...

jgoody · Aug 10, 2017

Thanks for all the input! The results from the test roll were that I got no vignetting with either of the lens hoods. And when I tried looking through the back of the camera didn't really see interference.

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