Tips Cameras Lenses Photography

Okay, I realize that some of you don't have SLR (Single Lens Reflex) cameras, and some of you that do don't have lenses to change out anyway, well who cares I'm going to talk about lenses anyway. Even with a point and shoot understanding your lens could help out with your photography. Also, I don't really know of an assignment to give for this one, so it can be some nice reading as your finishing up your composition assignment. This is also really long, just a lot of reading, so you may want to read it sections at a time. Especially since there is probably some confusing stuff in here.

Sensor Size

Okay before we can start talking about aspects of a lens we need to understand a little bit about our sensors. When the light comes into the lens and hits the medium to save the data on you get a different view based on how big that medium is. In most digital cameras, in all until you get high end models, your sensor is smaller than a frame on a roll of film. What does this mean, well just think of it as your camera cropping off the edges of what you would see in a film camera. Your camera should have documented somewhere how much this is, it is known as the crop factor. My camera has a crop factor of 1.5. This was confusing to me at first, but let me give you an example. If I put a 50mm lens on my digital camera and took a picture, then I wanted to take the same picture with a film camera, in order to see the same area I would have to use a 75mm lens, because the 50mm lens would have a bigger area, I would have to keep zooming in until 75mm to get the same area/crop that I had with the 50mm on my digital camera. I know this is hard to understand by reading it, so here is a fun place to play with what I am talking about. This website is a pretty good third party lens company, they make lenses and make them work with lots of different brands of camera. In order to help you choose the lens you need they have this tool. You can change the zoom to the desired spot, and you can choose digital or 35mm (film camera) to see what that lens would do on that type of camera. Check it out and play with it here until you get the hang of what I'm talking about.

Focal Length

Focal length is the distance from your lens to the medium, in our cases a sensor. These can range anywhere from 10mm to 1600mm, some lenses can go even lower or higher than that. Usually there are three categories that all lenses are placed into. The first category, on the lowest end, are your wide angle lenses. We've all heard of wide angle lenses right? These are the ones that are so wide, in some cases, that the edges of the picture start curving. When this affect starts happening they are also referred to as fish-eye lenses, because that is kind of how a fish sees things. These wide angle lenses are anything that has a focal length lower than 50mm in a film camera, or on my camera anything lower than 33mm, because of that crop factor we understand so well now. Basically just take the film number and divide it by your crop factor, most crop factors are 1.6. The next area are your normal lenses. These focal lengths are what "they" (who are they?) say our normal eye sees. In film terms this is anything between 50mm and 55mm, so on my digital it is between 33mm and 37mm. The last category are telephoto lenses, this is anything larger than normal, so anything above a 55mm, or in my case a 37mm is considered a telephoto lens. These values based on some simple math using arcs and stuff, you remember geometry, right, give us the number of degrees, or angle of view, we can see all at once looking through the lens, lets go over some of these values now, I'll just touch on some of the more popular values.

Focal Length 35mm Degrees Digital Degrees
14mm 114 92
33mm 66 44
37mm 60 40
50mm 46 30
55mm 43 27
75mm 32 20
135mm 18 11

I think you get the picture. If you notice the digital 33 is similar to the 35mm 50, thats good because above I told you those are basically the same field of view, which is shown here in the fact that they see the same number of degrees. Another thing to notice here, if you want wide angle shots you have an advantage with film, because the 14mm value will let you see more. If you like to get up close and tight from far away, then digital has an advantage because the 135mm value is a tighter shot on the digital camera. Understanding these values can help you determine what focal lengths you need to do the kind of shots you like. Those of you that like shooting portraits, which I think are a lot of you, you want somewhere between a 50mm and 88mm focal length, this is an unwritten rule, that is normally considered a good length, because you can give the person a little space and get a pretty normal perspective, or even a more narrow perspective, which we like because it makes us look skinnier. If you took a shot of a person with a 10mm lens they would stretch really wide, and I'm sure they wouldn't be too happy about that.

Types of Lenses

There are three different types of lenses, fixed focal length, zoom lenses, and macro lenses.

Fixed focal length lenses are kind of what they sound like, they are fixed in focal length, so a fixed 50mm lens, can only shoot at 50mm. These are also known as "prime" lenses. An advantage to prime lenses is the manufacturer knows what focal length you are always using so they can optimize the glass (oh side note photographers often refer to lens as glass, hey I need to get some better glass, that is some nice glass) to get a sharper picture, and they can often get you a wider aperture because they don't have to worry about all the different focal lengths. Our fixed 50mm lens has a max aperture value, I say max meaning how wide it can go, of 1.4. The disadvantage is that you need lots of these to get a good range of focal lengths.

If it isn't fixed, its a zoom. A lot of people think a zoom is a lens that gets you really close, but as I said above those are called telephoto, zoom is any lens that adjusts the focal length. So a 10mm-17mm zoom is a wide angle lens, and a zoom at the same time. The disadvantage of a zoom is that they are usually heavier, they usually have a "sweet" spot, a place where the lens is best optimized for a sharp picture, and unless you shill out the big bucks your aperture value usually isn't as wide, and it changes based on what focal length you have set, more on this later.

The last type of lens is a macro. This is really a different topic, but I think we can talk about it here, because there are fixed, and zoom macros too. The difference with a macro lens though, is it can focus closer up, so you can get those shots of ladybugs that fill the entire frame. Every lens you have has a certain point that it won't focus anymore, once you get closer than that value, it is different for each lens, it won't ever be able to focus. Macros are just optimized to let you get a lot closer than a typical lens will let you, and it isn't an easy thing to do, so macro lenses are usually a lot more money than a lens with the same focal length and f-stop range.

Compositional Affects

As I just mentioned as you zoom in your aperture value changes on most zoom lenses. That seems a little odd, the f-stop value is just the size of the aperture right? Isn't the aperture still the same size as you zoom in and out? Well, f-stop isn't only based on the aperture size, it is actually based on the aperture size and the focal length. The f-stop is the focal length divided by the aperture diameter. My kit lens, the one that came with my camera, has a max f-stop of 3.5-5.6. Its focal length range is 18mm - 55mm. So at a focal length of 18mm with an f-stop of 3.5 my aperture is at 5mm. Setting the focal length to 55mm with an f-stop of 5.6 my aperture is at 10mm. I'm not sure why the aperture can get wider as the focal length gets longer, but it is usually just they cheaper way they can make the lens, thats just how it happens to work out because of how they made the lens. If the lens is a zoom and can always have an f-stop of 2.8, they have to work a little harder to get the aperture to adjust correctly to get at the right diameter at every focal length, so these are usually more expensive lenses.

If what I said above was confusing, sorry, but what does this mean to you? Well it means that there is something else affecting your dof. Yes, you always thought that setting your f-stop was giving you total control over dof, well you're wrong, although it is a big part of it, it isn't the only thing affecting it. The way the f-stop is controlling it, is because it is changing the diameter of your aperture, but as I just described above, zooming in gets you a wider diameter too given the same f-stop. So again, the wider the aperture the shallower your dof. So a 50mm lens at 3.5 is a smaller aperture diameter than a 100mm lens is at 3.5. So the 50mm has a bigger dof, since the aperture is smaller. This means as you zoom you are also getting a smaller dof. There is actually a third thing that controls dof, the distance from you to the subject. If you are really close to things then the planes that your objects sit on are exaggerated more, your eye works like this too, if you are looking at a mountain really far away, there isn't much difference between the rocks and the trees, but if you are hiking tree to tree you can tell which one is further away, so the closer you are to your subject, the more shallow the dof. So a simple recap, if you want a really shallow dof, you want your maximum f-stop value (the smallest number because they are fractions), you want to be zoomed in as much as you can, and you want to get as close as you can. This will give you your most shallow dof.


Okay, lets talk about some things you can add to your lenses, for people with higher end point and shoots, like Julie, some of these will apply to you too.

We talked about macro lenses before, here are a couple of lower cost ways to try out macro photography, although they aren't as good as a nice macro lens, they do a pretty good job. The worst quality way to do macro photography is with magnifiers. These do just what you think they would, they magnify the image, making it look closer, kind of like a magnifying glass. The reason these aren't the best is because you now have more glass for the light to pass through, meaning you are probably losing quality, and less light goes through so you are losing some exposure too, but our cameras are smart enough to adjust for that. These can be bought at different values and you can stack as many as you would like to get more magnification. They screw into the end of your lens. Oh, anything that screws into your lens has to be the right size, and your camera should have the theta symbol and then the number, which is the diameter of your lens. My lenses are 49mm, 52mm, and 62mm. So when getting this stuff you need to know those values, that is the same value used to know what size lens cap you need if you ever lose yours. The next way to do macro photography is to get a reverse lens converter. One style of these you screw the converter onto your normal lens, usually a telephoto works the best, and then you screw another lens backwards onto the converter, this works like a magnifier as well. Again, you now have to worry about more glass. The last method, which is what I opted with, is a set of extension tubes. These go in between your lens and camera body and because they push your lens further away from the sensor you can get closer up and still focus. These are the best, next to macros, because you don't lose any quality as they are just hollow tubes. The biggest downside, you don't have much room for focusing, if you want to get further away, you have to start removing tubes, if you want to get closer you have to add tubes, but hey that is a small price to pay.

The next thing that you screw onto your lens are filters. Filters are what they sound like, they just filter the light, you can find a filter for just about anything you want. Some of the most common are UV filters, these block UV, but are mostly just used to protect your lens, because they don't really affect the shot much. Graduated filters, these are usually some color on top and by the time you get to the bottom they are clear. These are helpful for sunsets for example, if you have a red or orange graduated filter then the sky will get those darker sunset colors, while the bottom half of the shot will just be normal. ND(neutral density) filters are strictly just to filter out light, they are usually named based on how many stops of light they filter out. These are very helpful in getting those long shutter speeds for moving water in daylight. If our smallest aperture still makes our shutter speed a 125 that is too fast to get the flowing water, so we add a ND4 to take out 4 stops of light and now we are at a 4 shutter speed, which will give us that flow a lot better. The last type is one of my favorites called a polarizing filter. This takes out that polarizing affect you get when looking at water, where the light reflects off of it. If you have this filter, you can take away all the reflection and you can actually see right into the water. These actually work to take reflection off any non-metallic surface, like glass. They also have the added affect of making blues more blue, and greens more green.

Teleconverters are something that I wish I had to throw onto my telephoto zoom lens. These also go between your lens and body and change your focal length values of the lens. If you buy a 2x teleconverter and stick it on a 70mm-300mm lens, your lens is now a 140mm-600mm lens. These have the downside of more glass for the light to pass through, most people recommend not getting anything stronger than a 1.4x converter because they think any more and you lose too much quality.

The last extra, and most lenses come with these, are your lens hoods. Thes go onto the end of your lens and they block out any extra light that may hit your lens from outside of the view. This is commonly called sun flares, those little spots of light that just happen to get in pictures sometimes. If the lens hood is made right, you shouldn't get sun flares using your hood. Most photographers think you should always have your hood on, even in the dark, but I don't put them on too often because I am just too lazy to get them out, maybe I should work on that.


Sorry this was just a long boring post with no pictures. There is a lot to learn, so read it again in chunks until you understand it. If you don't have lenses or a camera that even has interchangeable lenses then this probably didn't help you much, but some of it should have. Again, this will just give you a nice break from assignments after that long composition assignment.