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Thread: General C mount sensor sizes?

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    General C mount sensor sizes?

    So I've begun shopping around for those industry cctv lenses and I have noticed that they are generally made for 2/3" sensors with the odd 1" sensor.

    Obviously I'd want to go for the larger one but just curious as to what were the sensor sizes for those old 16mm cmount lenses that everyone is using...1"? Just wanted to confirm.

    I currently have a 25mm Avenir cctv lens made for 1"sensors and there appears to be no signs of vignetting. There is a 12.5mm also made for 1" sensors. I would assume the image circle will stay the same offering a good alternative for a fast 12.5mm wide lens? Am I to assuming wrong because people say if you go lower than 25mm it then doesn't cover the sensor anymore which I find strange because if it was made to cover a 1" sensor it would always cover it if you know what i mean? i dunno. crazy aussie talking.

    cheers.

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    Re: General C mount sensor sizes?

    Coverage and illumination are different aspects to take into consideration.

    Even the 1" CCTV c-mount lenses do not cover the entire 4/3rds sensor, though many illuminate it completely thus giving the "unique" look.

    With the stacks of glass plates on the 4/3rds sensor and the presumable lack of microlenses, exacerbate the aberrations from the lenses giving rise to mush and swirl. The stacks also appear to spread the beam more thereby increasing the illumination area to more than a lens can offer (!).

    There isn't a c-mount lens of 12.5mm FL (1" or otherwise) that I know of that will even illuminate the 4/3rds sensor fully.

    The most talked about 12.5mm Cosmicars and Computars cover about 10 to 12mm circle and fail to illuminate the whole frame.

    If you want full coverage you need to look at the m4/3rds lenses with AF (and other lens corrections programmed in them) or Olympus pen F lenses and similar such lenses.

    If you want more control over focus, rendition and speed (focus and aperture!) then manual focus lenses are swell.

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    Re: General C mount sensor sizes?

    CCTVs don't currently come with 1" sensors which is why you will find mainly 1/2" and 2/3" C-mount lenses for CCTVs.

    There are far fewer C-mount lenses in 1" and ever fewer still in 1 1/3" (but there are some).

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    Re: General C mount sensor sizes?

    Quote Originally Posted by Vivek View Post
    There isn't a c-mount lens of 12.5mm FL (1" or otherwise) that I know of that will even illuminate the 4/3rds sensor fully.
    yeah, do you know why though? cause you would think if it is made for the same sensor size like 1" then it would have the same coverage as say a 25mm designed for 1" sensor?

    I'm gonna see if i can test fit some next week and see what i get.

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    Re: General C mount sensor sizes?

    They would cover 1" sensors but not the 4/3rds.

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    Re: General C mount sensor sizes?

    yeah i understand that bit. ok so by that reason the coverage that i see on my 1"sensor made lens now for the 25mm i should also expect to see on the 12.5mm version then? and if not why? diffraction angles because its wide...i'm just pulling words out of the air now...lol

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    Re: General C mount sensor sizes?

    I don't know.

    If you are looking for a ~12.5mm solution, this is what I use now-

    Olympus-D 17mm f/2.8 plus a Ricoh GW-1 = 12.75mm (use it at your own risk).

    Simply superb.

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    Re: General C mount sensor sizes?

    Quote Originally Posted by MRfanny View Post
    yeah i understand that bit. ok so by that reason the coverage that i see on my 1"sensor made lens now for the 25mm i should also expect to see on the 12.5mm version then? and if not why? diffraction angles because its wide...i'm just pulling words out of the air now...lol
    The image circle for the 1" vidicon is about 15.5mm, while it is a bit more than 21mm for Micro 4/3rds (4/3" vidicon).

    As a general rule, the longer the focal length is, the wider the coverage. Provided there is no mechanical obstruction, a 100mm lens to cover the 8mm ciné frame will usually cover the full 35mm photo frame. Most 25mm lenses more or less cover the 4/3rds sensor, not because they have to, but just because they happen to, because of their focal length. The aberrations on the edges prove that the lenses where not designed to cover such a large format.

    On the other hand, the lens designers have to struggle to create a 12.5mm lens that illuminates the whole image circle for a 1" vidicon. So there is no chance that the lens will also illuminate a larger format. And I don't speak of coverage...

    Cheers!

    Abbazz

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    Re: General C mount sensor sizes?

    Thanks Abbazz!

    Hey Vivek, thats interesting. So what issues would i be looking at with that Ricoh setup? Does it also work on the pana 20mm?

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    Re: General C mount sensor sizes?

    Quote Originally Posted by MRfanny View Post
    Hey Vivek, thats interesting. So what issues would i be looking at with that Ricoh setup?
    You need to attach a 37mm filter (without any glass) on the lens first before you can mount the GW-1.

    You will be attaching a ~80g converter on the 71g lens!

    I am waiting for some step rings and may be I will test the Pana 20/1.7 after that.

    The may be is because the Pana 20/1.7 focuses much slowly on its own either AF or MF. With any added weight it might not move at all.

    Also, Pana say not to leave the lens even attached to the body while storing. I think it is very delicate.

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    Re: General C mount sensor sizes?

    Quote Originally Posted by Vivek View Post
    I am waiting for some step rings and may be I will test the Pana 20/1.7 after that.

    The may be is because the Pana 20/1.7 focuses much slowly on its own either AF or MF. With any added weight it might not move at all.

    Also, Pana say not to leave the lens even attached to the body while storing. I think it is very delicate.
    The focus motor in the Panasonic 20mm appears to be very strong if the force of the lens retraction on power down is anything to go by.

    On the other hand, the Olympus 14-42 zoom is incredibly weak and any load of more than around 14g starts to tax the lens and 24g is painful to say the least. Finding a suitable lens hood for the this lens is difficult and the combo of a filter and lens hood is out of the question. Whacking a wide angle adapter on that lens would be impossible.

    BTW, how did this get into a thread about C-mount sensor sizes?

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    Re: General C mount sensor sizes?

    My sample is stiff, even for the pseudo manual focus.

    Also, you should read the instructions manual that comes with this plastic wonder.

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