Testing a Hood Before Waisting Film

[ruben]

I would like to post a simple and general question about estimating if a hood is appropriate or not.

Let's take for example an Helios standard lens, just for the example. If I mount a hood and I look through the rear left side of the lens towards the front right of the lens, and I do not see the hood borders: would this mean that hood will not vignette (and vice versa) ?

Thanks in advance
Ruben

 

[ferider]

Ruben,

I usually mount the lens to a camera and check in the film plane. Sometimes vignetting
only happens at certain apertures.

Roland.

 

[ruben]

Thanks Roland,

I am talking about widest aperture included. Perhaps for a language shortcomming I didn't understand you well: Did you mean your way of checking is better because it includes widest apertures, or that surprises may arise at any checking but with film ?

Sorry for the mess,
Ruben

 

[ferider]

Thanks Roland,

I am talking about widest aperture included. Perhaps for a language shortcomming I didn't understand you well: Did you mean your way of checking is better because it includes widest apertures, or that surprises may arise at any checking but with film ?

Sorry for the mess,
Ruben

No problem, Ruben. I have had a lens (notably the Canon 50/1.2) that does not vignette wide open, but
it vignettes at f4 anf f5.6, under certain hood/filter conditions. I cann't explain the physics ...

Best,

Roland.

 

[Spyderman]

I usually take the camera with lens and hood, then I open the back door and hold the shutter open on bulb.
Then I look through the front of the lens - whether I can see the corner of the frame when the lens is wide open and also with slightly stopped down diaphragm (up to fully stopped down). If I can always see the corner the hood should be OK, but if it's just so-so I don't use the hood...

 

[clintock]

Man I was doing it the hard way- taping a piece of thin paper to the film rails and checking what happend to the image projected on the paper when viewed from behind.

 

[ruben]

btw Roland, kindly notice besides your remark, that the angle of view created by viewing from the rear left and right sides of the lens is quite wider, and therefore the "test" more severe, than looking from the film plane...

But it prooves nothing I guess.

Cheers,
Ruben

 

[awilder]

Actually, the correct way to tell if a mounted lens hood vignettes (without using film) is to stop the lens down to the SMALLEST opening (f/16 or f/22), set focus at it's minimum, hold the lens infront of you at around arms length and slowly tilt it while looking front to back and stop when you can just see the back edge of the rear element. If the inside of the hood hasn't cut off the view of the rear elements edge, you're fine. If it has cut into it, recheck the same way but with the lens mounted to the camera and you are viewing the furthest corner of the film gate with shutter open at B or T. If you can just visualize the corner without the insde of the hood cutting off the view, you're fine. If it cuts into the view, change hoods.

 

[Finder]

Actually, the CORRECT way to see if a hood vignettes is to look through the corner of the film gate and see if the hood vignettes the exit pupil - just like you do with view cameras (anything outside the film area is not important). The aperture used for the test, is the aperture you are going to use. If you are using it wide open, test it wide open. Also, it will have more of a chance of vignetting at infinity rather than the minimum focus distance as the infinity position would be the shortest working focal length and so the largest angle of view.

 

[awilder]

FInder's correct on the infintity setting, however, using the smallest aperture allows more tilt in viewing from the front when you rotate the lens to ensure no vignetting occurs with the hood. In actual picture taking situations, you're more likely to see image cutoff when the lens is stopped down than when wide open especially if it's borderline when you don't know if it's the hood or normal falloff. Try it and see for yourself and then decide.

 

[Nickfed]

Gee, I don't want to sound too cynical about this, but has anbody actually put a standard hood on a standard lens and found it didn't work, really? Thats' what I would like to know as I submit that pretty well any hood you buy will work on a wide angle lens, so where's the problem? The only exception to this would be hoods like the Leitz FISON, clearly marked "Elmar 5cm" . I believe it, but if it actually works on an Elmar 35, remember where you heard it first.

My 55mm Takumar has a 46mm telescoping hood that has an i.d. of 52mm. It extends to 35mm and doesn't vignette, even if it's on a polarising filter. It is about at the limit. I recall it vignetted on a Yashica, but that might have been a 45mm.

So it makes you wonder about all the science. And it also goes some way to explain why it's been so hard for so long to find a hood for a 35mm wide angle lens.

 

[Doug]

Nickfed, your post recalled a mistake I made about hood coverage with a 35mm Auto-Takumar, the old f/2.3 version that takes 58mm-threaded hood. I found a very short untapered 58mm hood and ran a roll through the camera, vignetting every shot! Geez, I sure was surprised, as the hood was so minimal. Big front element, very narrow name-ring... I should have checked as severally described above! Live and learn; not every hood will work on a wide angle lens!

 

[Nickfed]

Yes Doug, I understand. But I bet most do work on a 35mm. And if it does, it will sure as hell work with a standard. The Helios the OP is worried about is over 50mm, as I recall it, and there is nothing unusual about its shape, so I guess the first thing to wonder about, is who on earth would make a hood the doesn't work with it? Or how could they?
In the light (ahem!) of the dearth of hoods specifically made for tele lenses, I think one can safely say - if a hood fits a Helios, it will work with a Helios. In the case of something that fell off a tele, you won't have to look too far too see that it doesn't. It'll be bleeding obvious.

 

[wolves3012]

Man I was doing it the hard way- taping a piece of thin paper to the film rails and checking what happend to the image projected on the paper when viewed from behind.

That's probably nearer to correct than peering through the lens from the back to see if you can see the hood!

Someone can tell me I'm wrong here if they can show me where but the field of view of a lens does NOT change as the aperture alters and changes only a little as the focus is altered. Therefore, vignetting is there or it isn't and it's dependent only on the field of view, which is itself a result of (fixed) focal length. Ok, so that's a slight simplification but it's close enough. Vignetting is more obvious as you stop down simply because the DOF increases and the shadow tends towards a hood image rather than a total blur darker area.

Putting some sort of screen at the film plane is a good way to see if there's a significant problem, maybe less so if it's subtle.

 

[Nickfed]

That's probably nearer to correct than peering through the lens from the back to see if you can see the hood!

No doubt about that

the field of view of a lens does NOT change as the aperture alters and changes only a little as the focus is altered.

Correct

Therefore, vignetting is there or it isn't and it's dependent only on the field of view, which is itself a result of (fixed) focal length.

Correct

Vignetting is more obvious as you stop down simply because the DOF increases and the shadow tends towards a hood image rather than a total blur darker area.

Correct

Putting some sort of screen at the film plane is a good way to see if there's a significant problem, maybe less so if it's subtle.

Correct. And a piece of film might do quite nicely

 

[sepiareverb]

I would mount the hood on the lens, and 'waste' a few frames- at the very worst I've never seen hoods vignette more than a tiny bit- a certainly acceptable (in all but the most demanding work) solution if these test frames did vignette would be a slight cropping.
Now putting a 50 hood on a 35 lens is going to vignette almost absolutely, but something close I wouldn't worry. I know Nikon AiS hoods were very interchangable- the same hood for 24 & 28, and it worked quite fine on a 35 as well. The current ZM hood for the 25 is for the 28 as well correct?
I prefer to test with film as you then have something to refer back too should something change later.

 

[ferider]

Someone can tell me I'm wrong here if they can show me where but the field of view of a lens does NOT change as the aperture alters and changes only a little as the focus is altered.

a little is relative. Just check on your 40 or 50mm lens how much physically
longer it gets when at close focus. Easily in some cases 5 - 10mm. So I think one has to check at infinity.

Therefore, vignetting is there or it isn't and it's dependent only on the field of view, which is itself a result of (fixed) focal length. Ok, so that's a slight simplification but it's close enough. Vignetting is more obvious as you stop down simply because the DOF increases and the shadow tends towards a hood image rather than a total blur darker area.

That is correct, but if you consider (see above) that vignetting is most
visible at infinity (largest FOV), you can compare the DOF of the lens
to the distance between front element and infinity. In the case of my
Canon 50/1.2 the hood shadow was not visible below f4.

Gee, I don't want to sound too cynical about this, but has anbody actually put a standard hood on a standard lens and found it didn't work, really?

For some lenses even a normal filter will cause vignetting. For others the "standard" hood is almost as expensive
as the lens.

Roland.

 

[wolves3012]

a little is relative. Just check on your 40 or 50mm lens how much physically
longer it gets when at close focus. Easily in some cases 5 - 10mm. So I think one has to check at infinity.

That is correct, but if you consider (see above) that vignetting is most
visible at infinity (largest FOV), you can compare the DOF of the lens
to the distance between front element and infinity. In the case of my
Canon 50/1.2 the hood shadow was not visible below f4.

Roland.

That was pretty much what I was getting at. I'd hazard a guess that the maker of a hood for (say) 50mm lenses would allow for focussing and leave a bit of margin to allow for people using it on (say) 45mm. Put a hood for an 85mm on a 35mm however and I think you can almost guarantee vignetting because it's completely wrong. For very wide-angles a cutaway hood (or sometimes no hood at all) are the only options, at which point I can't see the usefulness of any hood!

 

[ruben]

Yes Doug, I understand. But I bet most do work on a 35mm. And if it does, it will sure as hell work with a standard. The Helios the OP is worried about is over 50mm, as I recall it, and there is nothing unusual about its shape, so I guess the first thing to wonder about, is who on earth would make a hood the doesn't work with it? Or how could they?
In the light (ahem!) of the dearth of hoods specifically made for tele lenses, I think one can safely say - if a hood fits a Helios, it will work with a Helios. In the case of something that fell off a tele, you won't have to look too far too see that it doesn't. It'll be bleeding obvious.

hi Nickfed,
Regarding the Helios 53/1.8, I am looking for a hood SMALLER than the currently available vented one, 40.5 thread, (Heavystars is just one of the eBay sellers of it) which is too big to my taste. Finding other standard lens hoods 40.5 thread is indeed quite hard, unless you go for a pricy vintage one. I have not found any alternative, so I started to look for stepping rings to widen the possibilities. Hence the issue.

Cheers,
the "OP"

PS
what "OP" stands for ?

 

[Nickfed]

Hi

If you are looking at a step-up ring, you are simply further nullifying an already non-existant problem. If you are looking to step-down to a hood smaller than 40.5mm then clearly you deserve all the strife you are likely to get.
To add injury to insult, if the current crop of cylindrical "vented" hoods are like the Hoya and Astron originals, the hood itself only comes in two, or at most three, sizes and the variations made in the thread adapter and the size of the vents. In that case, changing thread size doesn't necessarily fix your problem, and the hoods are probably harder to find anyway. I say this because 40.5 was the most common thread size of the 1950s.
For all that, I use a 46mm polariser on a 49mm lens. Not a good idea, I just got lucky.

For what it's worth, and not really knowing what your tastes are, you might have a look in the video camera world. I saw a guy with a Voigtlander Vitessa recently, sporting a suspiciously modern-looking rectangular clamp-on hood, complete with cap. I bet it was off a digital video, and you can bet the Voigtlander's thread was 40.5.