Focal length and Macro lenses..why 105mm?

[Jredtugboat]

I have a question that I can't figure out. I believe it illustrates that I don't understand focal length as well as I thought I did.

When I think of focal length, I think of "small number = wide angle" and "large number = bring what's far away closer". When I think of "macro" I think of pushing the little flower button on my camera so I can take pictures of things centimeters away from the lens.

Why then would you use a 105mm macro lens on anything that is really close, ie., close enough to require a macro lens?

One friend said something like, "It has something to do with ratios".

The only other thing I have to go on is that I read somewhere, Once Upon a Time, that long focal lengths tend to distort images by making the distance between foreground and background seem compressed (is there a name for this effect?).

Any help on this would be appreciated.

Thanks!

[dwig]

Your confusion comes from having the wrong idea about what macro is. It has nothing specifically to do with distance from the lens although it often is done at close distances. There is one optical manufacturer that makes lenses for industrial use that will photograph, with a 35mm camera, areas smaller than 1x1.5" at distances up to 10 feet or so.

To start with, "macro" is not the proper word but is, none the less, the common term. In its common usage it roughly means "photomacography" but _NOT_ "macrophotography", an altogether different animal.

Common "macro" refers to taking pictures of small things, generally pictures with field of views around 1x1.5" to about 4x6". There are many reasons why you would want to do this with a WA and with somewhat of a Tele. The longer focal lenghts allow for greater working distance reducing the change of casting an unwanted shadow and offering what is generally considered better perspective.

Due to the nature of how the optical systems in zoom lenses work, it is easier for the lens manufacturers to get a macro function if they do it at the lens's WA settings. For this reason, the common macro button on a digital camera results in very close working distances since the macro is working at the WA end of the zoom range. Some digital cameras, like the Nikon CP950 & CP990 that I use regularily, allow access to the full zoom while in the macro mode. This allows me better perspective, at the tele end, for the jewelry photography that I do on a daily basis. A ladies' ring will fill the frame nicely at around 6-7".

[Ray Schnoor]

To start with, "macro" is not the proper word but is, none the less, the common term. In its common usage it roughly means "photomacography" but _NOT_ "macrophotography", an altogether different animal.

Just as photomicrography is photography of microscopic subjects, but microphotography is photography with a really, really small camerahttp://www.dcresource.com/forums/images/icons/icon12.gif

[dwig]

Just as photomicrography is photography of microscopic subjects, but microphotography is photography with a really, really small camerahttp://www.dcresource.com/forums/images/icons/icon12.gif

or more commonly, making very small prints. microphotography is what makes all of this possible. Large drafting of the conductor paths for integrated circuits are optically reduced photographically to make the very small "prints" are then etched into the silicon

[gary_hendricks]

Hey, I share your pain.

There's a book that'll clear this up for you once and for all.

It's called 'Macrophotography: Learning from a Master' from Ronan Loaec which is a wonderful resource. Read it and you'll never be confused again. :)

[Jredtugboat]

or more commonly, making very small prints. microphotography is what makes all of this possible. Large drafting of the conductor paths for integrated circuits are optically reduced photographically to make the very small "prints" are then etched into the silicon

Dwig,

Thanks for your insights. I think I'll have to do some more puzzling, but now I have a start, and I at least understand most of what you're talking about.