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Francesco Palombi

Recommendation - Projector with shard corners

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Hi,

 

I don't know much about film projectors.

When I see videos on youtube I often notice the super 8 projectors have very soft edges and corners.

 

Is there a projector that has instead sharp edges?

 

 

Thanks

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There's no way around this, because the film emulsion has to be in focus. The gate aperture, which is a milimetre or two in thickness, can't be sharp because it's not in the same plane of focus.

All projectors do this, which is why cinemas have black fabric screen masks to get a sharp edge.

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On 2/20/2019 at 7:09 PM, Mark Dunn said:

There's no way around this, because the film emulsion has to be in focus. The gate aperture, which is a milimetre or two in thickness, can't be sharp because it's not in the same plane of focus.

All projectors do this, which is why cinemas have black fabric screen masks to get a sharp edge.

Thanks for your answer, and sorry for the late reply, I didn't notice I got a response. 

 

I am assuming that the smaller the projection is and also the bigger the film size format is, the sharper the corners? am I right in this?

 

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No. You have cameras, printers, and projectors with sharp aperture corners and such with rounded corners.

A technician can lime the corners sharp, costs some money. If you produce thousand cameras, you can broach the aperture. Some aperture plates are just stamped, some are machined with end mills.

A picture of a camera gate with sharp corners aperture

1945985929_GateandapertureofGIC9.5camera.JPG.17acad714f525f0e99187aee1281113f.JPG

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1 hour ago, Simon Wyss said:

No. You have cameras, printers, and projectors with sharp aperture corners and such with rounded corners.

A technician can lime the corners sharp, costs some money. If you produce thousand cameras, you can broach the aperture. Some aperture plates are just stamped, some are machined with end mills.

A picture of a camera gate with sharp corners aperture

 

I think OP means sharp as in "in focus", not sharp as in right angled.

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5 hours ago, Simon Wyss said:

A technician can lime the corners sharp, costs some money. If you produce thousand cameras, you can broach the aperture. Some aperture plates are just stamped, some are machined with end mills.

Simon Wyss, Now that you mention this... Was there a reason for manufacturers to make gates with rouded corners? Are sharp corners more prone to scratching? I know there is a reason for sprocket holes to have rouded corners and it totally makes sense talking about film, but I don't see a reason to don't have sharp corners on gates, and because of that roundness I loose a few pixel lines on my scans. I may be greedy, but when shooting with small formats that is important.

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I always found rounded corners ridiculous but the vast majority of projectors has them. A bigger image area with cameras and a smaller one in projection was provided by the standards since the early 20th century. It works.

Mark, I was aware of the double sense and have chosen one meaning. I hope the focal side of the subject will be understood.

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I understand you are a camera technician Simon. Would you say it's safe to carefully file corners to make them sharp? I'm not going to do it with my NPR, but I may do it if I convert a K3 again.

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Well, Ruben, a mechanic knows how to do it. S/he does not use a file but an oil stone or a synthetic grindstone.

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16 hours ago, Simon Wyss said:

I always found rounded corners ridiculous but the vast majority of projectors has them. A bigger image area with cameras and a smaller one in projection was provided by the standards since the early 20th century. It works.

Mark, I was aware of the double sense and have chosen one meaning. I hope the focal side of the subject will be understood.

Thanks, now I got both sides of the subject 🙂

 

Without me opening another thread, can I ask if there s a chart for super 8 projector throw distances? Can't seem to find one. I'm thinking about very small projections (so I think long lens, will 33mm be enough and is there any longer lens for super 8?) 

 

Thanks a lot! 

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Thanks Simon, well I was thinking a fine file, then different grips of sand paper with water or oil and polish it at the end. I was curious about the reason for corners to be rounded that's all.

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4 hours ago, Francesco Palombi said:

Thanks, now I got both sides of the subject 🙂

 

Without me opening another thread, can I ask if there s a chart for super 8 projector throw distances? Can't seem to find one. I'm thinking about very small projections (so I think long lens, will 33mm be enough and is there any longer lens for super 8?) 

 

Thanks a lot! 

I was tempted to say LMGTFY, but everything seems to be for digital projection.

So  I've got my Samuelsons manual out.

Easy algebra OK?

w= (ad)/f

and

d= (wf)/a

where w= picture width (m)

a= projector aperture width (mm)

d= projector throw (m)

f= lens focal length (mm).

a for Super-8 is 5.33

So for a 1m wide picture with a 15mm lens you get a throw of 2.8m.

15-25mm is about standard for a projector zoom. There isn't a lot of interchangeability. They don't come much longer unless you have lots of £€$.

 

 

 

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On 3/21/2019 at 6:36 PM, Mark Dunn said:

I was tempted to say LMGTFY, but everything seems to be for digital projection.

So  I've got my Samuelsons manual out.

Easy algebra OK?

w= (ad)/f

and

d= (wf)/a

where w= picture width (m)

a= projector aperture width (mm)

d= projector throw (m)

f= lens focal length (mm).

a for Super-8 is 5.33

So for a 1m wide picture with a 15mm lens you get a throw of 2.8m.

15-25mm is about standard for a projector zoom. There isn't a lot of interchangeability. They don't come much longer unless you have lots of £€$.

 

great, thank you thank you!

On 3/21/2019 at 6:36 PM, Mark Dunn said:

 

 

 

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