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Julien Fallecker

collimationBeaulieu4008

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If the internal filter is removed it is a good idea to collimate the lens. Actually, it is always a good idea to have that done. Björn Andersson in Sweden can help you with that.

Filmkonsult Svebaco KB - Björn Andersson
Vidholmsbackkarna 54 - Box 5136 - 165 72 Hasselby - Sveriges
Telephone: +46 (0)838 1074
Email: bjorn.andersson@brevet.nu
info@beaulieu-service.com

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On 4/6/2019 at 8:21 PM, Julien Fallecker said:

Hello do you if collimation is obligatory or a extern filter could be use ?

Thanx

5

Don't bother with collimation after taking out the internal filter. It is just theory and witchcraft.

Many filmers  film  handheld and with ASA 100 film have apertures near f11. So what would be the point?

Just expose a bit of film at wide open aperture (use ND filter) while filming from a tripod. Find a subject at infinity and some other closer by and measure the distance which you set on the lens-scale. It that comes out fine you are fine.

BTW the very late models of 4008ZM4 which came without internal filter weren't adjusted with their C-mount machined off for a hair's thickness either

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17 hours ago, Will Montgomery said:

If the internal filter is removed it is a good idea to collimate the lens. Actually, it is always a good idea to have that done. Björn Andersson in Sweden can help you with that.

Filmko

Is it really good practice

to post other people's real life data which they themselves never posted before?

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1 hour ago, Andries Molenaar said:

Is it really good practice

to post other people's real life data which they themselves never posted before?

It's the first result on Google, so, yes. He put the information there.

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Posted (edited)
2 hours ago, Mark Dunn said:

It's the first result on Google, so, yes. He put the information there.

None of the results googles lists were originally posted by Anderson himself. It is most from over-eager forummembers and data harvesters who list business to business informatie. As I recall his own website merely functions as a footholder without any info. 

Edited by Andries Molenaar

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Quote

Don't bother with collimation after taking out the internal filter. It is just theory and witchcraft.

The "removing the filter then you have to collimate part may be witchcraft," but the point that a 4008 is what...35 years old and who knows what's been done to it is not witchcraft...always worth checking collimation every few years, especially if the camera is new to you. 

But if you test it and have no issues then save the money. Checking it should be part of regular service so if it's a new camera to you then service by someone who knows what they're doing is more important than just collimation.

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On 4/9/2019 at 6:52 PM, Andries Molenaar said:

Don't bother with collimation after taking out the internal filter. It is just theory and witchcraft.

Many filmers  film  handheld and with ASA 100 film have apertures near f11. So what would be the point?

Just expose a bit of film at wide open aperture (use ND filter) while filming from a tripod. Find a subject at infinity and some other closer by and measure the distance which you set on the lens-scale. It that comes out fine you are fine.

BTW the very late models of 4008ZM4 which came without internal filter weren't adjusted with their C-mount machined off for a hair's thickness either

It's actually physics, not theory or witchcraft!

A filter placed behind a lens will offset the back-focus by about a third of the filter thickness. In the case of wratten filters, which are usually 0.1mm, that's about 0.03mm difference. I usually collimate lenses to within 0.01mm, and the shorter the focal length the more critical back-focus becomes. So for a 6-66 zoom, an error of 0.03mm will definitely throw the wide end out when filming at maximum aperture. You may focus sharply at 66mm, but as you zoom out, the image will get softer. 

Now whether you notice this depends on what stop you shoot at, and whether you're shaking the camera about, as Andries mentions.  It's also possible that a lens is not perfectly collimated, or that the ground glass depth of the camera isn't exactly set to match the film plane, so even with the internal filter left in place there could be small errors. And of course Super 8 through a wide lens will have a lot of depth of field and natural softness, so gauging whether it's a bit softer than it should be can be tricky. The benefit of removing a crusty old filter probably does more good than the back-focus error introduced does bad. But if you want images as consistently sharp as the format and lens can produce at all f stops, it's best to have the whole shebang checked and adjusted as necessary. 

As an additional piece of evidence, your honour, to convince Andries that this is not just witchcraft, Bolex mentions in their manuals that placing a filter in the behind-the-lens filter slot will slightly alter the lens focussing. However on a Bolex the filter is in front of the reflex prism, so the alteration to focus happens to both film and viewfinder images. In other words (and as the manual goes on to say), using the reflex viewfinder will adjust the focus automatically. (They were also assuming the use of prime lenses on a turret Bolex, rather than a zoom lens.) By contrast, the reflex mirror on a Beaulieu 4008 is in front of the filter, so removing the filter affects the film plane but not the viewfinder image. So in this case the reflex viewfinder will now be out compared to the film.

 

 

 

 

 

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Posted (edited)

Considering how most film Super-8, it has no importance. It is often ISO 100+, aperture down to f11. Furthermore, it is often sloppy focusing and no tripods.

The rear retro focus lenses on the most used zooms stay in place (isn't it the thing used for 0.01mm collimation focusing) so there is no difference when it is on 6 or 66 focal length. Only with macro, the rear lens gets pulled in.

So if the camera runs fine just shoot a few frames from a tripod as described and see how these come out. 

Should you want reliable equipment for assignments you are better to get two working sets of equipment. That also covers theft, accidents or forgetfulness 🙂 Unless all the equipment gets involved here.

BTW it would be interesting to see if Beaulieu had the C-mount flange machined down on this very last production ZM4s as these were equipped with in-lens filters in their fitted Schneiders

Edited by Andries Molenaar

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excuse me my level of English does not allow me to answer you but thank you! saw your opinion dispute I will send him my camera and it will make a complete check up. I tested and indeed it is in wide angle that the image is soft. I would have liked for all the qualities of this jewel! but I do not forget that after so many years and format I can not make 16mm! but I love the super 8 and my Nizo also has a problem of sharpness.

thanx everybody for your help

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