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i have a quick question. We have a machine which has a camera mounted above a board at 75cm. The cameras ability to focus on an object at 0 zoom is 1cm, and all full zoom 120cm. The zoom is build into the camera and i have no idea what optic is on the camera at the moment. To reduce the focal length of the camera at full zoom we use an optic, this enables the camera to focus correctly whist fully zoomed in dispite it only being 75cm away form the camera(not 120cm). This optic is very very expensive however, http://www.edmundoptics.com/optics/optical-lenses/achromatic-lenses/mgf2-coated-achromatic-lenses/67-330

It works fine but i'm not sure we need this, is there way to firstly determine what optic is on the camera by the focal lengths given? and secondly what optic would need to be mounted on front of the camera in order to make the focal length at full zoom 75cm, as i can't take out the optic in the camera all ready i would like something to add to it to make up for the shortfall.

Sorry i'm a programmer and i have to get this camera focusing properly, my knowledge of physics is not great so apology's in advance for what is surely a poorly worded question

UPDATE

Sorry guys the camera im using in a Sony FCB-6500
http://pro.sony.com/bbsc/ssr/cat-camerasindustrial/cat-cihighdefinition/product-FCBEH6500/

I have also attached an image from the camera, its a grossing station however as you see there is the need to zoom in and study small object in great detail, at the moment tho the focus is no working so its blurry

This is an image from the camera

Thanks Again

Colm Clarke
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    I have read the question, and found not a mention of photography. It seems to be all about optics; even references an Edmund Optics catalog. One of the founding parties of the American Institute of Physics (AIP) was the Optical Society of America. (OSA) How can this question NOT be about Physics ?? –  Oct 23 '13 at 22:36
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    Crazy Buddy, im not really interested in photography, however the cameras we use are scientific and therefore need to be very accurate. As we are (and will ultimatley) need to use an optic, i'm looking for any suggestions that would help me identify the correct one. Also any ramifications that occur due to using that optic, ex image distortion, chromatic aberration etc. –  Oct 24 '13 at 14:30
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    Got an image of the camera? – jinawee Oct 26 '13 at 15:08
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    What camera is it and are you able to change the existing lens on that instead of adding your own elements? – James Snell Oct 26 '13 at 22:14
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    Hi Colm. Before we can offer any solid assistance, we really need to know exactly what you are referring to when you say "camera". Given the optical element you linked, I am going to venture a guess and say that you are using some kind of unique camera, and not something like a DSLR, Mirrorless, or Point & Shoot photography camera. We can probably help you, but we do need a bit more clarity first. Thanks! – jrista Oct 26 '13 at 23:22
  • As a side note, there are a few ways of changing focal length. Focal reducers, diopters, and extension tubes. Again, more information would be necessary to help you determine which one is best for your needs. – jrista Oct 26 '13 at 23:23
  • My favorite part of this question is where it says "I have a quick question". Lol. – dpollitt Nov 05 '13 at 13:09
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    This question appears to be off-topic because while it is about cameras, it isn't about cameras in a way that is likely to be of use for people using a camera for photography as opposed to as part of a scientific instrument. A comment even says "I'm not really interested in photography". – mattdm Nov 05 '13 at 14:07
  • I knew I had deja-vu here. – mattdm Nov 05 '13 at 14:26
  • Sorry but I didn't post this question here, i posted in on Physics stack exchange and some bright spark had it migrated here so if its not on topic blame them. – Colm Clarke Nov 08 '13 at 12:49

1 Answers1

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Your description of the camera is vague. If it a photographic one, the lens focal-range will be written on the lens in front or on the side of the barrel.

Regardless, the optics you use is not expensive compared to most. What you are looking for in photographic terms is a close-up diopter. They come in various strengths. Image quality is usually proportional to price. At Adorama for example, price ranges from $25 to 737 USD.

In order to get the right diopter you need to know the thread-diameter of your lens. It is also normally written on the lens barrel using next to the ⌀ symbol. If you don't find an exact size match, you can get a bigger one and bridge the gap using a step-up-ring.

Those items are easy to find at a dedicated photography store. Just search online at a store like Adorama. I mention them because they have a very extensive catalog. They also ship to most countries.

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