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Simple Lens Diagram

Jeffrey Rodgers , Dec 21, 1999; 03:23 p.m.

I am attempting to help beginners understand the terms used for camera lenses. There seems to be confusion about aperture and "f-stop". Is anyone intersted in seeing a diagram with explanation of terms used for a simple lens? I hope this helps... Click on my name and check out "portrait". Read text also.


Wayne DeWitt , Dec 22, 1999; 12:10 a.m.

You must have a point - I don't know what it is though. We tend to leave the "actual" aperture to the astronomers and the astrophotographers (I don't care if my 200mm f/4.0 lens has a 50mm aperture) - they care more than most other photogs. I guess we could all start saying "effective aperture" if it would make you happy. I would rather you spent your time explaining "t-stops" to people (it would help them to understand why a 5" 1000mm mirror isn't the same as a 5" 1000mm refractor), it would be more educational with regards to actual earth-bound photography. We use many misnomers in everyday language, it's just one more.

Jeffrey Rodgers , Dec 22, 1999; 01:50 a.m.

I don't really care if everyone uses proper optical terms. I just want them to understand how a camera lens works. I thought a picture would be helpful. However, a diagram of an actual camera lens would be better. Maybe some people are happy memorizing settings and techniques, but I like to understand how a camera lens works and why it works(or doesn't).

Wayne DeWitt , Dec 22, 1999; 10:35 a.m.

I stopped trying a long time ago to correct everyone I met on the usage of the word "aperture", they tend to look at you strangely after the monologue is over. I was serious about the "t-stop" thing though, I bet 9 out of 10 photographers (maybe 99 out of 100 in theses "auto-everything" days) are not aware that that they misunderstand the meaning of the term f-stop (as well as aperture). Didn't see reference to it on your site (forgive me if I missed it).

Alan Gibson , Dec 22, 1999; 11:37 a.m.

What you have called a 'field stop' is actually an 'aperture stop'. A 'field stop' would be at the focal plane.

Jeffrey Rodgers , Dec 22, 1999; 02:39 p.m.

OK, I am going to redo diagram showing an actual camera lens design. If anyone knows where I can find detailed info on lens elements & iris position of a common camera lens(50mm.)let me know. Sorry if I have caused more confusion to those of you trying to learn about lenses. In the meantime, I'm removing the diagram.

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