I bought a new 50mm lens, which is a "normal" focal length, not wide-angle or telephoto so that I can take photographs when it is almost completely dark at night. Like when people are looking through telescopes at night, at least on Long Island where there is so much light pollution. WARNING: Photography Lesson Ahead! So the opening in a lens that lets light through to the sensor in cameras is based on a system which I will spare you the explanation of. You're welcome! Suffice it to say, a lot of camera lenses have an opening expressed this way: f/4. If you pay more money, then you can get a lens that has a larger opening of f/2.8. That number is smaller, BUT that number means the opening in the lens is larger so more light can pass through. I know, I know, very confusing. The difference between f/4 and f/2.8 is twice the amount of light comes through. Pay more money and you can get an f/2 lens. Twice the light again, or four times the amount of light from f/4. And then if you really want the most amount of light, you can get a lens that has an opening of f/1.4 which will give you EIGHT TIMES MORE LIGHT! Don't worry, I bought a lens made in China and I don't know how they do that, but an f/1.4 lens that SONY makes goes for $1,298. Yikes. But my Chinese lens was only $377. It probably does not have the quality that the SONY lens has, but I bet most people would not know the difference. The thing about an f/1.4 lens is, that there something called "depth of field" and that means, when you focus on something, how far in front and behind what you focus on, will also be in focus. With an f/1.4 lens the sharp focus is only about 1/4", So I used my new lens in daylight and photographed this fern late in the day at f/1.4. The whole point of this blog, now that you are bored silly, is to talk about the soft focus effect I got by using that lens to photograph this fern. It is sort of in focus in the center, but becomes less in-focus as you move toward the edges. So I really like that effect. Whew, I sure used a lot of words to explain my soft-focus fern! Anyhow, here are two photos of the two lenses and you can see how much more glass is in the F/1.4 lens - a larger opening in front. And you can also see that the new lens is much larger than the other one, and, because of more glass, it is much heavier, but the weight and size are worth it. It is a magic lens!
End of lesson! Class dismissed! Thank you for your attention!
4 comments:
I got through your narrative OK but now I am exhausted. At least I had a rudimentary understanding of a lens F-stop before beginning today's lesson. I am pleased that I did not need to sit in the corner of the room wearing a dunce cap!
I tried to pay attention but my mind is tired reading all of this. Like that you photographed the lenses to show the big difference in size of glass.
Joan
Thank you, teacher, for your explanation. I’m glad that you explained the soft-focus because I thought my eyes were deceiving me as I looked at the ferns. There is such a difference between the amount of glass in the two lenses. Betsey
Rokinon makes terrific lenses. I thought for sure it would have been a manual focus, but I see it is an AF, Auto Focus lens. Have fun with your new lens and the extremely shallow depth of field at max open aperture.
Mark
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