Talk:Photographic lens

From Wikipedia, the free encyclopedia

	This article is within the scope of Wikipedia:WikiProject Filmmaking, an attempt to better organize information in articles related to filmmaking. If you would like to participate, you can edit the article attached to this page, or visit the project page, where you can join the project and/or contribute to the discussion.
B	This article has been rated as B-Class on the assessment scale.

1 Lens Classification

[edit] Lens Classification

Why is the classification of lenses meaningless ? This is based on objective datas. I'm not a great fan of zooms and I agree with the sentence that the best zoom (not lens) are your feet. But well this has senses have you ever tried to shoot handheld at 1/15s with a 300mm ? Or to make portraits with a 21mm ? Ericd 22:44, 7 May 2005 (UTC)

True, but I could create a new classification based on another type of objective data (e.g. focus range at a particular zoom); also, the current classification isn't what one would call scientific ("considerably smaller", "about the same", and "considerably larger" than the than the diagonal of the frame.) And finally, my whole point was that there is no classification when shooting: one just chooses a lens which matches the scene—and your examples illustrate that—, as opposed to some rigid lens "classes". And just to make my point clear: I wanted to write that paragraph for SLR newbies who must (IMHO) understand that the lens choice is theirs, and theirs alone, and it's not dictated in any way by some immutable laws. --Gutza 23:06, 7 May 2005 (UTC)

The classification and the explanation of it is awkward. There needs to be an explanation that lenses are intended for certain formats because of the circle of coverage within which an image does not have significant vignetting. For example, a 90mm lens would be telephoto on a 35mm camera, "normal" on a 6x7cm camera, and wide angle on 4x5 in. camera. However only the lens designed for the 4x5 camera could produce an unvignetted image on all three. A 90mm lens designed for a 35mm camera will produce a small image circle, too small for either of the other formats. Also noteworthy is the fact that because the 90mm wide angle lens is designed for the 4x5 format, it would not resolve as well in the center as a 90mm lens optimized for 35mm cameras.

[edit] "Nitpick"

My "Encyclopedia of Photography" defines a "telephoto" lens one that is shorter physically than its focal length would indicate, and the correct term for a lens that is significantly longer than the diagonal of the film area is "long-focus."

As an aside, "significant" in the above sentence refers to the fact that most normal lenses sold on SLR's for the 135 market ("35mm film") are 50-52mm in length- rather longer than the film diagonal of 42-43mm (film gate measurement).

This is adressed in Telephoto lens. Ericd 08:59, 19 October 2005 (UTC)

[edit] Is "objective lens" inappropriately redirected here?

It doesn't seem like an objective lens is the same as a photographic lens. Some objective lenses are not involved in photography, like those in microscopes and telescopes. -- Kjkolb 01:58, 10 November 2005 (UTC)

I changed it into a sub. -- Kjkolb 02:42, 10 November 2005 (UTC)

[edit] f-number and aperture diameter

I have edited the article slightly to remove the common misconception that the f-number is equal to the ratio of the focal length to the aperture diameter. It is not. The f-number is equal to the ratio of the focal length to the diameter of the entrance pupil of the lens. The latter is proportional to the diameter of the aperture. It is true that doubling the f-number halves the diameter of the aperture but it is not true that the aperture diameter is equal to the focal length divided by the f-number.--Srleffler 04:30, 14 February 2006 (UTC)

[edit] Camerapedia copying OK?

It's not plagiarism to copy the "free content" from camerapedia.org; however, the GNU license they use makes their material unsuitable for the wikipedia:

         Copyright (C) 2000,2001,2002  Free Software Foundation, Inc.
         51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
         Everyone is permitted to copy and distribute verbatim copies
         of this license document, but changing it is not allowed.

If changing the content is restricted, we can not use it here. Dicklyon 04:01, 6 July 2006 (UTC)

Erm, isn't it talking about the license, not content, when it says "changing it is not allowed"? --Imroy 04:12, 6 July 2006 (UTC)

Perhaps you're right. I had read it as "this licensed document", but I see now that's not what it says. OK, so why did you revert the content? Dicklyon 04:32, 6 July 2006 (UTC)

I didn't like a huge pile of content from a different site (and context) being copied verbatim into the article. It also had a lot of redundant information that was already covered in the article and other articles. Camerapedia looks like a useful resource, but I would prefer the information to be integrated into the article - carefully and with consideration of what is already in the article and other articles. Not just regurgitated with the simple click of a button. Wikipedia is not a mere dumping ground for random bits of information found elsewhere. The articles need to be well-written and well-laid-out, both within an article and the way in which information is broken into separate articles. --Imroy 05:06, 6 July 2006 (UTC)

The content of Camerapedia is under the GFDL, exactly like Wikipedia. --Rebollo fr 21:25, 26 July 2006 (UTC)