I own a Nikon D80 body....

I have a sigma 28 mm 70 mm DG 2.8

Is this a digital lens?

I want to buy a ultra wide angle lens. I found a

Sigma 10-20mm f/4-5.6 EX DC HSM Lens for Nikon Digital SLR Cameras

which is in my price range... and I only want to take outdoors photographs so the 4.6 is alright for me)

My question is: Is the mm size on both of these lens from a digital measure or is one of the old MM sizes with film camera.

I mean if I look at the 10-20 mm on the potential new lens
am I looking at the same numbers as the 28-70 mm lens?

I was told earlier that when I look at a digital mm I must multiply that MM 2.5 times the actual number on the lens.

for example if I had a 20 mm digital lens, the mm would really be 45 mm in the film lens. (I only understand the film mm's)

Sorry I am getting old......

I guess the simplest way for some of you to help me is to tell me whether this new 12 mm would be actually twice as small as the 28 mm on my other lens....

Thank you if you can figure this out enough to give me some help... I have saved my money for one year and I have enough and I am ready to order.. I live in a very remote area and there is not any camera shops near by. I do not want to spend my money to have to return the item....

Monte

I have a Sigma 10-20mm f/3.5 EX DC HSM that I like a lot. I use mine on a Canon camera that has a 1.6 crop factor, so it acts like a 16-32mm on my camera. One made for your Nikon would be a 15-30mm. I think you will find that more than adequate for wide angle.

Since the DC lenses Sigma makes will only work on a camera with a crop factor, I don't know why they don't put the "actual range" on the barrel. It would make things a lot less confusing. Putting the 35mm equivalent on a lens you can't properly use on a full frame (35mm) camera seems silly to me.

Sigma also makes a less expensive 10-20mm, so you might want to look at it too.

I am really new to the photography terminology. What exactly does "crop factor" mean?

I own a Nikon D80 body....


Most of us are shooting with cameras that have an APS-C sized sensor (Canon 7Ds, Nikon 7000Ds, etc.) instead of a full frame (35mm) sensor, primarily because of cost, but sometimes because of camera body size, or something else. When you buy a lens, the size of the lens is stated in a 35mm size. For example if you buy a lens that says it is a 135mm, that is a 135mm on a full frame camera. If you are using a Canon, Nikon, Pentax, Olympus, Sony, etc. that is not full frame (35mm), you have to multiply 135 buy the crop factor of your camera body. My Canon has a 1.6 crop factor, so the lens acts like a 216mm lens on my camera. Non full frame Nikons have a 1.5 crop factor, so the lens would act like a 202.5mm on them.

Thomas,

So if I am looking at a 10 mm lens, It is a 15 mm (crop factor 1.5) on my Nikon D80. Yes?

A "full frame" DSLR refers to any body that has a digital sensor of the same physical dimensions as 35mm film, that being 36mm x 24mm. Any DSLR with a smaller sensor is referred to as a "crop" sensor body because the smaller sensor in effect "crops" the image available from the lens rather than giving you the full image it is capable of.