lense width question

[Sean Maroney]

im not a very good judge of lense capabilities...here's a question hopefully someone more knowledgable could help me with...on one of my cameras,the lense goes from: 5.5mm-88mm.. even with a wide angle adapter, it just isn't very wide for my needs....now, i have a chance to get a canon lense that goes from 7-112mm(for a different camera)....how much more width am i gaining- at the pictures widest point -between the two lenses???? doesn't seem like much to me at first glance, but then again like i said, im not that good at judgeing these things....thanks

[Kevin Randolph]

The easiest way to tell would be to set the two cameras side by side, open both up all the way and see what you get through the viewfinder. That being said, you probably don't have access to the canon lens before buying it (mail order?).

The relationship between the chip size and the lens measurement is going to be what you would look at. For example, on a 35mm film camera (still image) the width of the frame is actually 36 mm and the height is 24 mm. The measurement across the diagonal (say upper left corner to lower right for instance) is 50 mm. It just so happens that when a 35mm camera is fitted with a 50mm lens, the field of view is a very close approximate to the human eye's field of vision. This is what's known as a "Normal" lens. On a medium format still camera the human eye approximate is an 80mm lens (larger negative).

So, to answer your question, it depends on the chip size (negative size) of each camera. If your current camera has a chip size of 1/6 of an inch and the Canon has a chip size of 1/3 of an inch, then I believe that the Canon lens (at 7mm) would deliver a wider image than the first camera you mention (at 5.5mm). The real "standard" that you'll want to find out for each lens is their 35mm equivalent. That is to say, what would the measurement of each lens be if it was for a 35mm camera. For instance, I have a Canon XL2 with the 20x lens that came with it. The actual lens measurement is 5.4 - 108mm, but the 35mm equivalent is 42.3 - 846mm. So you can see that this is not really a "Wide Angle" lens as the 35mm equivalent measurement is 42.3mm (not that much smaller, i.e. wider, than 50mm). That's why the Canon sells a 3x lens for the XL Camera series.

But then you have the other variable that you mentioned - the wide angle adaptor. There are several different wide angle adaptors on the market. Almost all of them will have a number rating on the lens - 0.6x, 0.8x, 0.3x and the like. This number is to let the user know how much wider the adaptor will make the image. This is done by multiplying the lens measurement (in your case 5.5mm) by this number (5.5mm X 0.8 = 4.4mm). But the trick is to know the 35mm equivalent and use that number so that you're comparing apples to apples.

The 35mm equivalent may be in the owner's manual for your camera, if not you may be able to find it on the manufacture's website. The 35mm equivalent for the Canon lens that you want to buy should either be available directly from the seller, or by searching it's manufacture's website. Either way, you need to compare apples to apples.

I hope this helps, Sean. And to all those out-there that may have more experience, if I've misstated something please let me know.

Thanks,
Kevin

[Sean Maroney]

thanks kevin...now i know why im not very good at the whole lense thing...i can't do any sise by side comparisons yet since i haven't received the lens yet, but hopefully with a x.8 wide angle attached, i will be in better shape then the gy110's....thanks again

[Steve House]

Originally Posted by Sean Maroney

im not a very good judge of lense capabilities...here's a question hopefully someone more knowledgable could help me with...on one of my cameras,the lense goes from: 5.5mm-88mm.. even with a wide angle adapter, it just isn't very wide for my needs....now, i have a chance to get a canon lense that goes from 7-112mm(for a different camera)....how much more width am i gaining- at the pictures widest point -between the two lenses???? doesn't seem like much to me at first glance, but then again like i said, im not that good at judgeing these things....thanks

You're not gaining "width" with the new lens, you're losing it. The low numbers are the wide angle part of the spec and 5.5mm is a wider angle view than is 7mm. The big numbers are the telephoto end, the bigger they are the more the image is magnified and the narrower the field of view. While Kevin is correct in his discussion of the effect of the size of the image area (film area or image sensor) on how much of a wide angle or telephoto you get for a given focal length lens when comparing different cameras, if both the 7mm and the 5.5 lenses are compared on the same camera, the lower numbered lens will always be the wider angle. As he points out, a 150 mm lens is very much a telephoto lens on a 35mm camera but is a wide angle lens for a 4x5 view camera. OTOH, a 20mm lens is a wider angle than is a 35mm lens when both are mounted on a 35mm camera.

Now, even more to the point, are you sure the Canon lens is even going to fit on your camera?

[Kevin Randolph]

Steve,
When I suggested that Sean may be able to gain width with the 7mm lens, I was making the assumption that the Canon camera that he would use it on had a 1/3 inch CCD and that his current camera had a 1/6 inch CCD. So a technically narrower lense on a CCD about 4 times the size (inverse square law) of the first should yeild a wider field of vision.

"So, to answer your question, it depends on the chip size (negative size) of each camera. If your current camera has a chip size of 1/6 of an inch and the Canon has a chip size of 1/3 of an inch, then I believe that the Canon lens (at 7mm) would deliver a wider image than the first camera you mention (at 5.5mm)."

However, you are correct in that if both cameras have the same size CCD then the 5.5mm lens would be wider, even moreso with a wide angle adaptor. This would be why Sean would need to provide more information about each camera that he has for anyone to give him a straight forward answer about witch would be wider.

Thanks,
Kevin

[Steve House]

Originally Posted by Kevin Randolph

Steve,
When I suggested that Sean may be able to gain width with the 7mm lens, I was making the assumption that the Canon camera that he would use it on had a 1/3 inch CCD and that his current camera had a 1/6 inch CCD. So a technically narrower lense on a CCD about 4 times the size (inverse square law) of the first should yeild a wider field of vision.

"So, to answer your question, it depends on the chip size (negative size) of each camera. If your current camera has a chip size of 1/6 of an inch and the Canon has a chip size of 1/3 of an inch, then I believe that the Canon lens (at 7mm) would deliver a wider image than the first camera you mention (at 5.5mm)."

However, you are correct in that if both cameras have the same size CCD then the 5.5mm lens would be wider, even moreso with a wide angle adaptor. This would be why Sean would need to provide more information about each camera that he has for anyone to give him a straight forward answer about witch would be wider.

Thanks,
Kevin

Yep, and I had the impression too that rather than buying a Canon camera and lens, he was buying just the Canon lens all by itself, intending to mount it on his current camera in place of the existing 5.5mm lens. Setting aside the fact that very few DV cams even HAVE interchangeable lenses, I'd first worry about whether the lens mounts would be compatible.