My lenses have various markings written on them. It’s about time I learned what those mean!

My first lens is the AF-S DX Zoom-NIKKOR 18-135mm f/3.5-5.6G IF-ED. On, the following lines are written “AF-S Nikkor 18-135mm 1:3–5.6G ED” and “DX SWM ED IF Aspherical ∞–0.45m/1.48ft ⊘67″.

My other lens is the AF-S DX VR Zoom-NIKKOR 55-200mm f/4-5.6G IF-ED. It has written on it “AF-S Nikkor 55-200mm 1:4–5.6G” and “DX SWM VR ED IF ∞–1.1m/3.61ft ⊘52″.

What do these mean?!

The easy part is the Nikkor part. A Nikkor is a camera lens by Nikon.

The mm number is the length of the lens. Since these are zoom lenses (thus the zoom in the lens names), they have ranges. 18-135mm for one lens, and 55-200mm for the other.

The 1: number is the aperture, which is listed as “1:3–5.6G ED” for the lens with a maximum aperture range of 3.5–5.6 (depending on zoom). The other lens lists “1:4–5.6G” with the len’s maximum aperture range being “4–5.6″. I don’t know what the “G” stands for. I don’t know why the former lens lists “ED” at the area, while both lenses list it elsewhere (so I’ll address it further down).

The AF-S refers to the len’s “AF-S (Silent Wave Motor)”, which is also what the SWM on the lens refers to.

The DX is mentioned on the lenses pages on Nikon’s site as being a “compatible format” with “DX”. My guess is that this means it’s compatible with the D-series of Nikon cameras, such as my D40.

The latter camera’s VR refers to the “vibration reduction” technology.

The IF means the lens has “internal focusing”, and the ED is “extra-low dispersion”, a glass element which “minimizes chromatic aberrations, contributing to superb contrast and resolution performance.”

Nikon’s page for the former of my two listed lenses lists “Aspherical (Elements): 0″, yet the lens has the word “Aspherical” right on it. Nonetheless, this probably refers to it having an aspherical lens, which is something I know nothing about.

The ⊘ part (with the line actually passing through the cicle on both sides) refers to the filter and lens attachment size. The ⊘67 is for a 67mm filter or lens attachment, and the ⊘52 is for 52mm filters and lens attachments.

The ∞–m/ft gives the minimum focus length, in meters and in feet. Maybe the ∞ is the maximum focus length? As for minimum, my former lens cannot focus on anything closer than 1.5 feet, and my latter lens cannot focus on anything closer than 3.6 feet.

I understand a lot of this now, but I sure didn’t “get” any of it before I had the Nikon D40 and used these lenses!

I should have saved one of the photographs showing it, but there was a piece of dust showing up in my photographs. This isn’t the first time it’s happened, and I know it won’t be the last.

My first thought when seeing a spot in the viewfinder was that it was on the lens. Switching to another lens, however, did not “remove” the spot. This means it was on the camera itself.

I’m not sure how it happened when I haven’t swapped lenses recently, and the spot wasn’t there until today. Maybe there was dust inside, and it “fell into place” when I moved the camera?

The solution? I removed the lens, and in the camera is a rectangle piece of glass. I lightly brushed that with a lens brush, then put the lens back on. Pointing the viewfinder to the clear, blue sky (a good place to find spots of dust on a lens), I found the dust was no longer there.

Another spot of dust bites the dust!

Most sellers on eBay sell a DSLR camera in a “kit”, with “kit lenses”. Typically there is a lens used for most common photography, and a second lens Often there will be an attachment for a wide angle lens, and another for a telephoto lens.

There are so many lenses out there! The terminology can be confusing, and I have a lot to learn. From 18-55mm to 55-200mm, 28-80mm to 75-300mm (numbers in millimetres); from f/3.5-5.6 to f/4.0-5.6. What does all this mean? Before I make any purchases, I must know this information!

Focal Length

According to Wikipedia, focal length is:

The focal length of a lens determines the magnification at which it images distant objects.

Wikipedia continues:

How focal length affects photograph composition: adjusting the camera’s distance from the main subject while changing focal length, the main subject can remain the same size, while the other at a different distance changes size.

Three images are shown on the Wikipedia page displaying exactly the effect I was trying to produce yesterday. In an image on Wikipedia, it’s shown that a photograph can be taken at 18mm showing a subject and background. By moving the camera (back farther from the object?) and using 34mm, the subject remains the same size, but the background becomes larger relative to the subject. Another movement of the camera relative to the subject, and switching to 55mm, keeps the subject the same size while the background is even larger.

Therefore, using different lenses and keeping the same size subject in each photo, a lower mm will have a farther background, and a higher mm will have a closer background. In other words, the higher the mm, the closer the object becomes.

When I look at eBay listings, I find cameras with mm from 18-55mm to 28-80mm are called “wide angle” lenses. The 70-300mm lenses are referred to as “telephoto” lenses.

My reading informs me that a low number, such as 20mm, is good to photographs of architecture. This is the “extreme wide angle” lens. When moving into the 20’s and early 30’s of the mm, you’re in the “wide angle” territory, which is useful for landscape photography. The rest of the 30’s, and up through about 70mm, the “normal” range, would be for most photos, photos taken on the street, or of trees and other forest nature. Moving up throgh the 70’s, up to about 135mm, is the “medium telephoto”, and this is for taking portrait photographs. Moving over 135mm, and up to 300mm and even beyond, takes you to the “telephoto” range, and to taking moving photos, such as wildlife and sports.

Can I even remember any of that? From buildings to landscape to normal to portrait to action.

When a camera lists two mm’s, this means it can zoom from one to another (“zoom lenses”). There are also non-zooming lenses (“prime lenses”) which cover only one mm, which must require the photographer to move around a lot more to get the right position, distance, and focus!

Aperture

The other number on a camera is the aperture. This can be f/3.5-5.6, f/4-5.6, and so on. These numbers refer to how much the len’s view opens to let light in. A high number such as f/8 is a small opening, and lets in very little light. A low number such as f/1.4 is a large opening, and lets in a lot of light. So, the larger the aperture, the smaller the opening, and the less light gets in. The smaller the aperture, the larger the opening, and the more light gets in. Not one bit confusing!

Practically, a higher “f-stop” number will require a slower shutter speed, to compensate for less light entering the lens. This gives a wider depth of field. A lower f-stop number can get by with a slower shutter speed, as more light enters the lens, and the result is a narrower depth of field. Maybe I will remember this after I’ve seen it in action a number of times. I think the important thing for me to keep in mind is that a lower number means a narrower depth of field, which leads to a blurry background and (depending on how the photo is taken) close foreground, putting the primary focus on the subject in the middle. This is a common depth of field of a macro photograph.

When to Use Which Lens

With a wide angle lens, I should be able to take photographs of landscape. Foreground objects take the center stage, and background fades off into the distance.

Using a telephoto lens, farther objects are brought closer. Were I taking photos at a sports event, this would bring the action to me.

What would be important for me would be a macro lens, for closer-up photography. These lenses, while similar to the “normal” lens, are able to focus must closer to the subject. Their focal length is often about 55mm, but a higher number such as 100mm allows macro of farther objects. This is probably used for photographs of insects, so they can be shot from farther away, so as not to scare them away, while still getting that prized macro photograph.

Another type of lens is the fish-eye lens, which makes a photograph look as it was reflected off of a drop of water. The edges of the photo round out, skewing the proportions. I haven’t seen any application of this lens on a photograph that I’ve found to be interesting, so I won’t buy one of these.

Closing Thoughts

I’ll probably buy a “kit” which will come with a normal lens and a telephoto lens, as well as attachments for telephoto and wide angle. If the normal lens doesn’t give me the quality of macro photographs I want, I would then start reading up on macro lenses. The reason for this method of buying is because it appears it would be much cheaper in the long run than buying things separately, considering that I would get use out of both kit lenses.