Super Wide Problem

January 10, 2007

So I encountered a funny problem while shooting a 2 camera Betacam job today. Our superwide Canon 4.5 was 'seeing' itself b/c it was TOO wide. I'm wondering why that was. I couldn't believe the lens was designed to 'see' it self. We had to zoom in all the way to around 15mm to lose all of the vignetting caused by the lens. Was there something I missed? I tried flipping the doubler on and off to see if the trigger was stuck, I tried everything else I can think of that might be getting in the way...any ideas? Is it possible some glass element got loose and caused the lens to 'see' more than usual?

Any insight would be greatly appreciated. Besides feeling a bit red from this happening in front of a client, Really I'm hoping there's nothing wrong with the lens.

Best,

Chris

Jonathan Bowerbank · January 10, 2007

Vignetting usually happens with cheap fisheyes that aren't constructed wide enough for the camera's own elements or even in some cases, its own.

In this News posting at this website you can see an example of a good fisheye/extreme wide angle lens: http://cinematography.com/forum2004/index....showtopic=19182

You can see that it expands out and above & beyond the camera's own lens elements to prevent any vignetting.

Edited January 10, 2007 by Jonathan Bowerbank

Jim Feldspar · January 10, 2007

So I encountered a funny problem while shooting a 2 camera Betacam job today. Our superwide Canon 4.5 was 'seeing' itself b/c it was TOO wide. I'm wondering why that was. I couldn't believe the lens was designed to 'see' it self. We had to zoom in all the way to around 15mm to lose all of the vignetting caused by the lens. Was there something I missed? I tried flipping the doubler on and off to see if the trigger was stuck, I tried everything else I can think of that might be getting in the way...any ideas? Is it possible some glass element got loose and caused the lens to 'see' more than usual?

Any insight would be greatly appreciated. Besides feeling a bit red from this happening in front of a client, Really I'm hoping there's nothing wrong with the lens.

Best,

Chris

" tried flipping the doubler on and off to see if the trigger was stuck"

I've used a fair amount of video cameras but what is the "doubler" ?

January 10, 2007

" tried flipping the doubler on and off to see if the trigger was stuck"

I've used a fair amount of video cameras but what is the "doubler" ?

It doubles the focal length of the lens, with a loss of light however.

Also, this lens I was using wasn't cheaply constructed. I've used Canon 4.5s plenty with no problem. And this was the same type of lens. Anyone have an idea of what the problem is?

Broatch Berry · January 22, 2007

It doubles the focal length of the lens, with a loss of light however.
Also, this lens I was using wasn't cheaply constructed. I've used Canon 4.5s plenty with no problem. And this was the same type of lens. Anyone have an idea of what the problem is?

I think the problem might be that the Canon len's has a crossover for use on cameras that have the option to shoot 4x3 or 16x9, if I remember the last Canon lens I used with the crossover had a small dial that said

16x9-4x3 to use this function and how it worked was when you were in the 4x3 mode on a 16x9 camera, you could dial in the crossover to give you the 20% you lose on your wide end on the camera in the 4x3 mode! but if you went back to 16x9 mode on the camera and you did not set the crossover back to 16x9 on the dial you would get the vignette in lens from the crossover bieing on for the 4x3 setting.

I hope this helps

Broatch

Broatch Berry · January 22, 2007

I think the problem might be that the Canon len's has a crossover for use on cameras that have the option to shoot 4x3 or 16x9, if I remember the last Canon lens I used with the crossover had a small dial that said
16x9-4x3 to use this function and how it worked was when you were in the 4x3 mode on a 16x9 camera, you could dial in the crossover to give you the 20% you lose on your wide end on the camera in the 4x3 mode! but if you went back to 16x9 mode on the camera and you did not set the crossover back to 16x9 on the dial you would get the vignette in lens from the crossover bieing on for the 4x3 setting.

I hope this helps

Broatch

So if you are shooting with a none widescreen betacam camera (4x3) and have a crossover lens for dealing with the 20% loss on the wide with a widescreen camera shooting 4x3, leave the crossover off! or the doubler crossover will vignette your lens on your 4x3 only betacam.

I think that what I wanted to say

Broatch

Daniel Sheehy · January 22, 2007

I've used a fair amount of video cameras but what is the "doubler" ?

2x focal length extender.

The lens is for the appropriate sensor size...?

January 24, 2007

So I found out the problem. First of all, you are correct that this was a cross-over lens. Some of these lenses have a design 'flaw' in that element can get 'stuck' between the 16:9 and 4:3 mode b/c of something with the doubler mechanism thus causing a vignetting problem. What you have to do is a two step solution. First turn the dial over to 16:9 on the cross-over and then flip the doubler on and off a few times. Then switch back to 4:3 mode and the vignetting is gone. Also, I should mention the lens was actually a Fuginon 4.8 not a Canon 4.5. Sorry for the confusion and thanks for the responses!

Jonathan Bowerbank · January 24, 2007

What you have to do is a two step solution. First turn the dial over to 16:9 on the cross-over and then flip the doubler on and off a few times. Then switch back to 4:3 mode and the vignetting is gone.

Funky

Brian Drysdale · January 24, 2007

Funky

There was a brief fashion of shooting shots with the doubler (x2) in the half way position, so that you had the wacky effect of two images superimposed at difference focal lengths. You could get some neat effects.