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Light loss with canon 814


jon lawrence
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the problem with Sankyos... are that they are truly not great cams and doesent really produce great images but ofcourse it is allowed to dream.....

 

not sure if the name is spelled Sankyo or S-I-M-P-L-E or Santo.......

 

 

shoot.....

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the problem with Sankyos... are that they are truly not great cams and doesent really produce great images but ofcourse it is allowed to dream.....

What is your specific complaint about Sankyo, and in particular your complaint about image quality? Image quality would generally be a Lens issue. It could also be the Aperture. Since most or all Sankyos don't have a Prism, this is a plus for image quality.

Did you actually own a Sankyo, and if so which Model?

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That is big of you, I accept. Attached below is a list of "S" Manufacturers. Mine is the Super CM400 Model which is actually as old as me. I cannot believe that someone was able to buy that Model on eBay for only $26 US Dollars, but that could be dated back to Aug. 1999. I can only assume that Sankyo designed and patented their mirror-fed Viewfinder, and it's probably on all of their post-1969 Models. If any modern Camera Manufacturer should become smart enough to make a limited run of new S8 Cameras, they could use this mirror-fed Viewfinder since the Patent is long expired.

 

That was a joke! (Apologies for my irony, I thought the word marvellous might give it away but...)

 

The real irony is I used to have a Sankyo CM 400 it came with another camera I bought. I shot a cart of K40 with it to verify it worked and gave it away. Now I wish I had kept it so that I could take it apart to show you the prism, which despite Matthew's assertion I am confident would be there.

Edited by jacob thomas
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That was a joke! (Apologies for my irony, I thought the word marvellous might give it away but...)

 

The real irony is I used to have a Sankyo CM 400 it came with another camera I bought. I shot a cart of K40 with it to verify it worked and gave it away. Now I wish I had kept it so that I could take it apart to show you the prism, which despite Matthew's assertion I am confident would be there.

HA! :lol: HA! :lol: HA! :lol: HA! :lol: HA! :lol: HA! :lol: HA! :lol:

Oh Jacob, you are truly a Doubting Thomas. :blink: Was yours a regular or Super CM400? Do you think that Matthew and I are lying about the Mirror in the Diaphragm Chamber? If you accept our assertion about the Mirror -- which would have no other purpose but to feed the Viewfinder, then why would the Camera need a Prism in front of the Film Gate? The light path to the Viewfinder could have a Prism to feed the Light Meter. In the near future I will be removing the Lens to clean it inside, and I will be able to further verify your error. I've been meaning to get a Webcam, and when I do I will try to take (and post here) a digital Picture through the Lens so that you can see this "fantastical Mirror" with your own eyes. Until then, I refer you to the professional opinion of Matthew's Sankyo Model:

"Sankyo's flagship model, features a unique 'Hi-Focus' Dichroid Focusing System, making this the sharpest focusing Super 8 camera in existence. An extremely rare camera." HA! :P

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I love my camera. B)

Mattie, I've come up with an absolute way to verify that Jacob's "fantastical Mirror" is for the Viewfinder. If you shine a Flashlight through the Eyepiece, the light will reflect onto the Mirror and out the Lens. My Camera has a second larger Mirror on the top of the diaphragm chamber facing upwards. It can only be for the Light Meter. Look inside your Lens again to see if you have that top Mirror. If you look really hard through the open Aperture, you'll be able to see the Shutter or the Film (if the Shutter's open) at the back. It's obvious that there's no prism.

For everyone else, if you shine a Flashlight through the Eyepiece you can determine if you have a Prism.

 

...Now I wish I had kept it so that I could take it apart to show you the prism, which despite Matthew's assertion I am confident would be there.

<_< :lol:

My good man Jacob of Auckland,

I do believe and declare that it is meet and proper for thee to now acknowledge thy complete and unmitigated error in stating that Sankyo Cameras have prisms and fantastical mirrors and the like -- thereby questioning and mocking mine competence. In furtherance thereto, but only in the event of the failure of such acknowledgement from thee, as men of honour I do believe that we shall have to resolve this matter definitively and with finality in the form of a Duel. God Save the Queen!

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Getting back on topic - does anyone know how much light is lost by a Canon 814 due to the viewfinder? I just bought one & am waiting for some suitable batteries for the meter. In the meantime I'd like to do some tests using a Sekonic incident as a benchmark.

I'm guessing 1 stop of light is lost to the finder, but I can't find any confirmation.

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  • 2 weeks later...

OK, question on the mirror idea. I have a Bolex H16 that came with a Pan Cinor 17.5 - 70. It's a reflex lens. There is a tiny mirror in the center of the image area that scoops out some light and aims it at a prism that throws the image at about 30 degrees down the viewfinder tube. At least that's how I understand it from looking at it. Now mind you the prism is only to bend the image to the eye, not in the lens to film path.

 

Still, doesn't adding a mirror, half silvered mirror or anything in the path degrade the image somewhat? I don't want to keep tossing all this down a rabbit hole but unless it is a true reflex camera where the mirror flips out of the path during the opening of the shutter, it's all affecting the image in some small way right?

 

S.

Edited by Sean McHenry
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Getting back on topic - does anyone know how much light is lost by a Canon 814 due to the viewfinder? I just bought one & am waiting for some suitable batteries for the meter. In the meantime I'd like to do some tests using a Sekonic incident as a benchmark.

I'm guessing 1 stop of light is lost to the finder, but I can't find any confirmation.

 

 

I just did a camera test with an 814 on saturday. I did some bracket exposures, comparing the BTL to my spot meter. I should be able to gleen something from this. I have to say while I was shooting I was suprised at how close my spot meter readings and the BTL meter readings were. Anyway I'll let you know how it comes out.

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OK, question on the mirror idea. I have a Bolex H16 that came with a Pan Cinor 17.5 - 70. It's a reflex lens. There is a tiny mirror in the center of the image area that scoops out some light and aims it at a prism that throws the image at about 30 degrees down the viewfinder tube. At least that's how I understand it from looking at it. Now mind you the prism is only to bend the image to the eye, not in the lens to film path.

 

Still, doesn't adding a mirror, half silvered mirror or anything in the path degrade the image somewhat? I don't want to keep tossing all this down a rabbit hole but unless it is a true reflex camera where the mirror flips out of the path during the opening of the shutter, it's all affecting the image in some small way right?

 

S.

 

Don't worry about some of the things you've read in this thread; if it's in good condition all the half-silvered mirror should do is absorb some light. You don't have a reflex Bolex, so the only way you can have reflex viewing is with a dog-leg finder like the one you have.

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I have a Bolex H16 that came with a Pan Cinor 17.5 - 70. It's a reflex lens. There is a tiny mirror in the center of the image area that scoops out some light and aims it at a prism that throws the image at about 30 degrees down the viewfinder tube. At least that's how I understand it from looking at it. Now mind you the prism is only to bend the image to the eye, not in the lens to film path.

 

Still, doesn't adding a mirror, half silvered mirror or anything in the path degrade the image somewhat? I don't want to keep tossing all this down a rabbit hole but unless it is a true reflex camera where the mirror flips out of the path during the opening of the shutter, it's all affecting the image in some small way right?

Are you talking about a Mirror in the Diaphragm Chamber that you can see when looking inside the Lens?

If so, the Mirror should be in front of and below the center of the Aperture Opening. The Light Rays which expose the Film converge at the center of the Aperture Opening. A Mirror below that point of convergence will not affect the Light going through the Aperture. The Mirror provides a separate light image to the Viewfinder which has only minor vertical parallax to the light image going to the Film Gate. If you have a Webcam, post a low-resolution Picture of your Mirror.

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O.K. looked at my footage from the test of my 814XL-S that I did on Saturday. The BTL seems to work just fine, and I was getting a difference of 1/3 to 1/2 of a stop between my hand held spot meter and the BTL, with the BTL being more open than the hand held, which makes perfect sense.

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Are you talking about a Mirror in the Diaphragm Chamber that you can see when looking inside the Lens?

If so, the Mirror should be in front of and below the center of the Aperture Opening. The Light Rays which expose the Film converge at the center of the Aperture Opening. A Mirror below that point of convergence will not affect the Light going through the Aperture. The Mirror provides a separate light image to the Viewfinder which has only minor vertical parallax to the light image going to the Film Gate. If you have a Webcam, post a low-resolution Picture of your Mirror.

 

There's no parallax with a reflex finder. That's the point. The partially-silvered mirror intercepts the entire pencil of rays- it's not above or below- and diverts some of it to the viewfinder. It's that simple.

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O.K. looked at my footage from the test of my 814XL-S that I did on Saturday. The BTL seems to work just fine, and I was getting a difference of 1/3 to 1/2 of a stop between my hand held spot meter and the BTL, with the BTL being more open than the hand held, which makes perfect sense.

Thanks Douglas.

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There's no parallax with a reflex finder. That's the point. The partially-silvered mirror intercepts the entire pencil of rays- it's not above or below- and diverts some of it to the viewfinder. It's that simple.

This is not the same type of Mirror that I have in my Sankyo. Where is this Reflex Mirror located in the Diaphragm? I would like to see a picture of it.

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I'm afraid it is the same type. Perhaps someone is prepared to saw a camera lens in half in order to check.

 

Of course the partially-silvered mirror appears to extend a little above or below the centre of the lens- it's got to be attached to the barrel somewhere, it can't hang in space. But that doesn't mean it doesn't intercept the entire pencil of rays. It does and it must, otherwise the finder image would be cropped.

 

It's a while since I studied lens design so I can't point you to a specific reference, but might I recommend Sid Ray's books "The Lens and all its Jobs" , "The Lens in Action" and "Applied Photographic Optics".

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I'm afraid it is the same type. Perhaps someone is prepared to saw a camera lens in half in order to check.

 

Of course the partially-silvered mirror appears to extend a little above or below the centre of the lens- it's got to be attached to the barrel somewhere, it can't hang in space. But that doesn't mean it doesn't intercept the entire pencil of rays. It does and it must, otherwise the finder image would be cropped.

I don't know why you're referring to the aggregate light image as a "pencil", but there is not just one light image passing through the Lens. The total number of images is monumental. The perfect light image goes through the center of the Aperture. All the other images have varying degrees of parallax. The "image" produced by a Lens is comprised of "perpendicular" Light Rays. Non-perpendicular Rays produce the other images. When there is low light, a larger Aperture lets in "parallel" Light Rays which are immediately next to the perpendicular Rays. These parallel Rays are not perfectly perpendicular. A person's Eye works the same way, but without an Aperture. The Eye has "rods" to filter out non-perpendicular Rays. You can look it up further in an Encyclopedia.

 

I explained earlier on in this Thread how the Sankyo Mirror works to intercept a separate light image -- separate from the central image which exposes the Film. The Sankyo setup has no impact whatsoever on the image exposing the Film. If the Reflex Mirror Sean refers to is the same as the Sankyo Mirror, then it has no impact on the exposing image. Having not seen his Camera, I can't say if it's the same -- nor can you say since you haven't seen my Camera either. It is possible to look through the Lens without cutting it in half.

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A person's Eye works the same way, but without an Aperture. The Eye has "rods" to filter out non-perpendicular Rays. You can look it up further in an Encyclopedia.

 

Iris/pupil acts as an aperture. You can look it up further in an encyclopedia.

Wikipedia: Pupil

Wikipedia: Iris

 

As for how a lens works see Wikipedia: Lens.

Edited by jacob thomas
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I don't know why you're referring to the aggregate light image as a "pencil", but there is not just one light image passing through the Lens. The total number of images is monumental. The perfect light image goes through the center of the Aperture. All the other images have varying degrees of parallax. The "image" produced by a Lens is comprised of "perpendicular" Light Rays. Non-perpendicular Rays produce the other images. When there is low light, a larger Aperture lets in "parallel" Light Rays which are immediately next to the perpendicular Rays. These parallel Rays are not perfectly perpendicular. A person's Eye works the same way, but without an Aperture. The Eye has "rods" to filter out non-perpendicular Rays. You can look it up further in an Encyclopedia.

 

I explained earlier on in this Thread how the Sankyo Mirror works to intercept a separate light image -- separate from the central image which exposes the Film. The Sankyo setup has no impact whatsoever on the image exposing the Film. If the Reflex Mirror Sean refers to is the same as the Sankyo Mirror, then it has no impact on the exposing image. Having not seen his Camera, I can't say if it's the same -- nor can you say since you haven't seen my Camera either. It is possible to look through the Lens without cutting it in half.

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I don't know why you're referring to the aggregate light image as a "pencil", but there is not just one light image passing through the Lens. The total number of images is monumental. The perfect light image goes through the center of the Aperture. All the other images have varying degrees of parallax. The "image" produced by a Lens is comprised of "perpendicular" Light Rays. Non-perpendicular Rays produce the other images. When there is low light, a larger Aperture lets in "parallel" Light Rays which are immediately next to the perpendicular Rays. These parallel Rays are not perfectly perpendicular. A person's Eye works the same way, but without an Aperture. The Eye has "rods" to filter out non-perpendicular Rays. You can look it up further in an Encyclopedia.

 

I explained earlier on in this Thread how the Sankyo Mirror works to intercept a separate light image -- separate from the central image which exposes the Film. The Sankyo setup has no impact whatsoever on the image exposing the Film. If the Reflex Mirror Sean refers to is the same as the Sankyo Mirror, then it has no impact on the exposing image. Having not seen his Camera, I can't say if it's the same -- nor can you say since you haven't seen my Camera either. It is possible to look through the Lens without cutting it in half.

I don't know why you're referring to the aggregate light image as a "pencil", but there is not just one light image passing through the Lens. The total number of images is monumental. The perfect light image goes through the center of the Aperture. All the other images have varying degrees of parallax. The "image" produced by a Lens is comprised of "perpendicular" Light Rays. Non-perpendicular Rays produce the other images. When there is low light, a larger Aperture lets in "parallel" Light Rays which are immediately next to the perpendicular Rays. These parallel Rays are not perfectly perpendicular. A person's Eye works the same way, but without an Aperture. The Eye has "rods" to filter out non-perpendicular Rays. You can look it up further in an Encyclopedia.

 

I explained earlier on in this Thread how the Sankyo Mirror works to intercept a separate light image -- separate from the central image which exposes the Film. The Sankyo setup has no impact whatsoever on the image exposing the Film. If the Reflex Mirror Sean refers to is the same as the Sankyo Mirror, then it has no impact on the exposing image. Having not seen his Camera, I can't say if it's the same -- nor can you say since you haven't seen my Camera either. It is possible to look through the Lens without cutting it in half.

 

The term 'pencil of rays' is a standard one in optics, as you would find out if you did a little study of the subject.

 

I have thought long and hard about whether or not to say the following in a public forum, and have previously given you the benefit of the doubt, but in the interests of alerting novice posters to your singular notions, here goes. Hopefully the moderators will not remove this post too soon.

 

I'm sorry, but this stuff about different images is preposterous. It defies the laws of physics. It's not helpful of you to confuse novice posters with such balderdash. Your camera is NOT designed according to your unique conception of optical principles different to all others. The eye has an aperture- it's called the iris, as Jacob correctly pointed out. The 'rods- are the receptors in the retina insensitive to colour. They've got nothing to do with 'filtering out non-perpendicular rays'. Any encyclopedia which told me what you have would go straight in the bin.

 

I have every sympathy with your wish to help those less knowledgeable, but you cannot invent your own parallel universe of physical laws and principles to do so. The rest of us are stuck in this one.

 

Having got this off my chest, I will try to stay away from your posts in future. But I will respond if I think you are misleading anyone else.

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I have thought long and hard about whether or not to say the following in a public forum, and have previously given you the benefit of the doubt, but in the interests of alerting novice posters to your singular notions, here goes.

 

I have every sympathy with your wish to help those less knowledgeable, but you cannot invent your own parallel universe of physical laws and principles to do so. The rest of us are stuck in this one.

 

The times I've read this subforum, I've stayed out of it for the same reasons but I agree. This is supposed to be a serious professional forum and should be committed to scientific and technical accuracy whether S8, 35, HD...

.

 

-Sam

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The term 'pencil of rays' is a standard one in optics, as you would find out if you did a little study of the subject.

 

I'm sorry, but this stuff about different images is preposterous. It defies the laws of physics. It's not helpful of you to confuse novice posters with such balderdash. Your camera is NOT designed according to your unique conception of optical principles different to all others. The eye has an aperture- it's called the iris, as Jacob correctly pointed out. The 'rods- are the receptors in the retina insensitive to colour. They've got nothing to do with 'filtering out non-perpendicular rays'. Any encyclopedia which told me what you have would go straight in the bin.

 

I have every sympathy with your wish to help those less knowledgeable, but you cannot invent your own parallel universe of physical laws and principles to do so. The rest of us are stuck in this one.

If you've seen that term "pencil of rays" used in specific books, then fine. I've never seen that term used in regards to light. It sounds like a layman's term. Yes, the Iris in the Eye widens and narrows like a Camera Aperture in order to accommodate varying Light Conditions. However, the Eye still needs Rods to provide a decipherable image! Last time I checked, a Camera does not have Rods! You seem to be confused as to how a Lens (both in the Eye and a Camera) produce a Light "Image". The central Image is comprised of those Light Rays which are perpendicular to the Lens and travel through the center of the Aperture! Do you know the difference between a perpendicular and non-perpendicular Light Ray hitting the Lens? Are you not aware that there are hundreds of millions of Light Rays hitting a Lens at any one time? Do you understand how a Light Image is produced from these millions of Rays? I'm afraid that you don't fully understand how light works. You need to study up further on the topic. I can't spend any more of my time trying to educate you. I'm afraid that you are doing the misleading.

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Below is a drawing to make things more understandable. There are 4 Points marked on the Sphere (a Lens of course is a portion of a Sphere). I've marked two Light Paths through each Point -- 90 & 85 Degrees. As you can see, the 90 & 85 Degree Paths converge at two points. The 90 Deg. (perpendicular) Path goes through the center of the Aperture, and this forms the "image" which exposes the Film or CCD. In reality, only a f/22 or higher would provide perfectly perpendicular Light Rays. The 85 Deg. Path hits the Aperture Plate, and doesn't expose the Film. This 85 Deg. Path produces a "parallax image" -- slightly off the central image. The Sankyo Mirror simply uses one of these parallax images to feed the Viewfinder, and it only causes minimal vertical parallax. Thus, your central image for exposing the Film is not touched! This is a fantastic ideawhether or not Mark, Jacob and Sam can understand it.

 

lightpth.jpg

 

As for this "partially-silvered mirror" you refer to, you need to explain further what you're talking about.

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Below is a drawing to make things more understandable. There are 4 Points marked on the Sphere (a Lens of course is a portion of a Sphere). I've marked two Light Paths through each Point -- 90 & 85 Degrees. As you can see, the 90 & 85 Degree Paths converge at two points. The 90 Deg. (perpendicular) Path goes through the center of the Aperture, and this forms the "image" which exposes the Film or CCD. In reality, only a f/22 or higher would provide perfectly perpendicular Light Rays. The 85 Deg. Path hits the Aperture Plate, and doesn't expose the Film. This 85 Deg. Path produces a "parallax image" -- slightly off the central image. The Sankyo Mirror simply uses one of these parallax images to feed the Viewfinder, and it only causes minimal vertical parallax. Thus, your central image for exposing the Film is not touched! This is a fantastic ideawhether or not Mark, Jacob and Sam can understand it.

 

lightpth.jpg

 

As for this "partially-silvered mirror" you refer to, you need to explain further what you're talking about.

 

This thread reached an impasse quite a while ago now. Is there an authority who you would accept being corrected by, perhaps they would be so kind as to step in and resolve this somewhat surreal difference of opinion (on a question of fact).

 

As for partially silvered mirror (often also referred to as pellicule mirror) again check wikipedia:

Wikipedia: Partially Silvered Mirror

 

If you want a good layman's explanation of how the eye works I can recommend the chapter in Richard Dawkins Climbing Mount Improbable on the evolution of the eye.

 

Dawkin also explains how only one image is formed in the eye and not an infinite jumble of images as you seem to believe: it's called a lens. The other option for extracting only one image from the infinite rays of light bouncing around in all directions is a pinhole.

 

Good luck

Edited by jacob thomas
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