please helps shead some light on lens specs.

[Badams]

FOR GIVE ME FOR ASKING A DUMB QUESTION.....
But Ive been looking at camera lens for awhile now and cannot figure out for the life of me what F, USM, IS, EF, MM means.
an Exaple of this follows:

"28-200MM F3.8-5.6 "
and
"28-135MM F/3.5-5.6 IS USM EF"

thanx,

BJ

[timmciglobal]

F means the F stop or apature at max of the lens. (or min apatur to be technical) basically Lower F numbers mean more light comes threw lens means faster shuttters. F 2.8 is faster (more light) then F 3.5. F3.5-5.6 indicates at the wide angel setting it is F3.5 at fastest at zoom setting F 5.6.

IS is image stabilization which reduces the effects of camera shake and lets you shoot at slower shutter speeds while still getting sharper pictures. It is not magic, if you have 1/200th a sec shutter speed without image shake and the lens has IS it could probably do 1/100th reliably due to the IS system.

EF is the mount of the lens. New canon SLR and dSLR take EF and eF-s mounts.

USM means ultrasonic motor. Significantly faster focusing speed and far less noise then non USM or non canon lenses. This doesn't effect "focus ability" but rather speed of focus search the lens itself has to do.

Tim

[Rhys]

FOR GIVE ME FOR ASKING A DUMB QUESTION.....
But Ive been looking at camera lens for awhile now and cannot figure out for the life of me what F, USM, IS, EF, MM means.
an Exaple of this follows:

"28-200MM F3.8-5.6 "
and
"28-135MM F/3.5-5.6 IS USM EF"

thanx,

BJ

In addition to what has already been explained, mm means millimeters.

[Badams]

thanks alot guys.... Another Q I have is how do you know how far millimeters are, so like if I wanted to get a 200mm lens how far would that go? Someone told me that a 100-200mm lens is equal to the human eye.

[nate]

thanks alot guys.... Another Q I have is how do you know how far millimeters are, so like if I wanted to get a 200mm lens how far would that go? Someone told me that a 100-200mm lens is equal to the human eye.

I have no idea how to compare the focal length of a lens with the human eye. But this page will answer your questions: http://consumer.usa.canon.com/app/html/EFLenses101/focal_length.html

[Badams]

On that page , what does the degrees stand for? is it the focal point?

[Badams]

Are there any good sites that anyone can reccomend that tell you about MM size?

[Rhys]

Are there any good sites that anyone can reccomend that tell you about MM size?

I thought the human eye could see about 28-35mm. After that everything is magnification. So, a 300mm lens will be a 10x magnification from what you can normally see...

[nate]

On that page , what does the degrees stand for? is it the focal point?

The degrees is the field of view when looking through the lens. A telephoto lens will isolate a small section in front of you, which is only a few degrees. A wideangle will include much more to the sides, so it is a much larger angle. If you had "perfect" peripheral vision, and could see everything from your left shoulder to your right shoulder, you'd be seeing 180 degrees (a half-circle).

Degrees aren't talked about much in photography -- Canon just put those on there for reference. Study that chart to get an understanding of focal lengths though (the MM), because those are essential. For your reference, a 50 mm lens is considered "standard", as it has a very similar field of view to the human eye. To calculate magification power, divide a focal length / a short focal length. So a 200mm lens will make any given object appear 4x bigger than it would in a 50mm lens (4x = 200/50).

[Badams]

so, what your trying to say is that a 200mm lens is 4x more powerful than that of a 50mm? So, in other words the higher you go in mm the closer you get? vs the smaller the mm the further away you get?

[Badams]

so, when buying a zoom lens one needs to keep in mind how close they wanna go and also keep the (F-stop) in mind as well?

[nate]

Yes, that's right.

Some people like a zoom that covers a big range, such as 18-200mm lenses by Tamron and Sigma. The advantage of this is convenience (not having to switch your lenses) and relatively low cost. The disadvantage is that the optical quality doesn't quite match lenses that are prime or only cover a smaller focal range. Also, the "mega-zooms" tend to have slower maximum apertures than primes or zooms that cover a smaller range.

[Badams]

Im weighing heavily on getting a Sigma lens. Im thinking about getting the Sigma - 70-300mm f/4-5.6 APO Zoom Macro Super II Lens for Canon AF now, looking at this one, it looks to me like it would be 6x more powerful than the one that I have right now which is the canon 18-55mm. Plus it looks like its a macro lens too. now, the only Q I have is that what is "APO" does it have somthing to do with the macro lens or what?

[George Riehm]

Im weighing heavily on getting a Sigma lens. Im thinking about getting the Sigma - 70-300mm f/4-5.6 APO Zoom Macro Super II Lens for Canon AF now, looking at this one, it looks to me like it would be 6x more powerful than the one that I have right now which is the canon 18-55mm. Plus it looks like its a macro lens too. now, the only Q I have is that what is "APO" does it have somthing to do with the macro lens or what?

I believe that APO is Sigma's abreviation for Apochromatic which means a lens virtually free from chromatic aberration, aka CA or "purple fringing".

http://www.daviddarling.info/encyclopedia/A/apochromatic.html

The Sigma 70-300 APO is a good choice for a consumer grade long telephoto lens at a reasonable price. It's not really a macro lens, as it only focuses down to 1:2. Apparently there is a 58mm adapter for this lens that will allow focusing down to 1:1. A true macro lens will focus down to 1:1, but many manufacturers are streching that term these days. Also you will see the terms macro and micro both referring to this function.

I suggest that you Google on the terms you want to learn as that is the quickest way to get all of this stuff.

Hope that helps.

[ReF]

i've also heard many times that 50mm is about equal to what the human eyes see. a 50mm lens on a film camera with a large bright viewfinder, the objects seen through the viewfinder appear pretty much the same size as with the naked eye. if i look with both eyes (one looking through the viewfinder) things look pretty much like they do without the camera. keep in mind that 50mm on a digital SLR isn't really 50mm anymore due to the 1.6 crop factor. plus those viewfinders are a bit small as well.

that 1:2 macro rating (half life size) on the sigma is pretty damn good, especially considering that it's at 300mm and the pricing as well. heck, true macro lenses only go up to 180mm (as far as i know) and cost around $700. the canon version is $1200.

[cwphoto]

F means the F stop or apature at max of the lens. (or min apatur to be technical) basically Lower F numbers mean more light comes threw lens means faster shuttters. F 2.8 is faster (more light) then F 3.5. F3.5-5.6 indicates at the wide angel setting it is F3.5 at fastest at zoom setting F 5.6.

IS is image stabilization which reduces the effects of camera shake and lets you shoot at slower shutter speeds while still getting sharper pictures. It is not magic, if you have 1/200th a sec shutter speed without image shake and the lens has IS it could probably do 1/100th reliably due to the IS system.

EF is the mount of the lens. New canon SLR and dSLR take EF and eF-s mounts.

USM means ultrasonic motor. Significantly faster focusing speed and far less noise then non USM or non canon lenses. This doesn't effect "focus ability" but rather speed of focus search the lens itself has to do.

Tim

You were right the first time - maximum aperture or minimum aperture value

EF-S will only work on some Canon DSLRs, namely the EOS 20D, EOS 300D/Digital Rebel, and EOS 350D/Digital Rebel XT.

Rule of thumb for IS is three stops.