Lens markings deciphered

[urfslam]

All,
I'm looking for a resouce to help me understand how to use the markings on my lenses. I'm not talking about the manufacturers acronyms that tell you what the lens does (G/D, AF-S, DX etc.) but the ones dealing with depth of field, reproduction ratio (1:1.2, 1:3 etc.). Any help would be appreciated.

Urf

[Prospero]

The markings regarding the reproduction ratio of a lens work as follows. If you focus on a certain distance, the lens will indicate the distance it is focussed on and sometimes a reproduction ratio (This happens mostly with primes, but with some zooms it is only indicated for the long end of the lens). Reproduction ratio indicates to what ratio a object located at the focussing distance is reproduced on the sensor.

For example, when I set my Sigma 70-300 at 300mm and I focus as close as possible, it will indicate that the subject is 0.95 meters away and that the reproduction ratio is 1:2. This means that object is twice as large as its projection on the sensor. A flower with a diameter of 2 cm will be 1 cm on the sensor.

The markings for depth of field will indicate the depth of field if the lens is focussed on the hyperfocal distance. This is mostly done in landscape photography. If you focus on the hyperfocal distance with a given apperture, the largest possible region will be in focus.
You can focus on the hyperfocal distance by alligning the infinity mark on the distance scale with the marking for a certain apperture.

Here's a picture I found on the internet of the 50 f/1.8:

http://homepage.mac.com/davebeaman/.Pictures/hyperfocal.jpg

In the second picture, you see a lens that is focussed on the hyperfocal distance if you were shooting at f/22. Notice that the infinity symbol is alligned with the line numbered 22. On the other side of the thick line, you see the same numbers. You can see that the number 22 is alligned with a distance of approximatly 2m on the distance scale. This distance is the near limit of the depth of field.

You can conclude from this that if you shoot at f/22, and focus on the hyperfocal distance, the depth of field will extend from 2m away to infinitly far away.

The hyperfocal distance can be useful for landscapes when the scene has very close objects as well as thing near infinity. The hyperfocal distance is then a good compromise. I seldom use it myself. I find that focussing on a object at a medium distance works just as well.
The markings can not help you determine the DOF at other focussing distances. Also, at smaller appertures than f/11 or f/22 it is hard to get an accurate result, because for larger appertures the hyperfocal distance as well as the near limit will approach infinity.

I hope this is clear.

[erichlund]

Actually, the hyperfocal distance is a poor choice for lanscapes. The human eye naturally perceives things close in focus, with a gradual loss of focus and resolution with greater distance. In a photograph, if everything, near, middle and far, is all in focus, then the picture will look flat. The scene will appear with more depth if you try to match what the eye naturally sees.

You want your foreground far enough away to give a reasonably deep depth of field, but still focus on the foreground.

Many newer lenses don't include hyperfocal distance markings.

[urfslam]

Thank you gentlemen. I appreciate the help. Do you know of a little booklet or something of the sort that has been published? I'd like to have something for reference.

Urf.

[K1W1]

Probably your library or even a second hand book store.
Pre 1980 when auto focus first appeared every book on photography had this sort of information in it because you needed to work these things out for yourself. The numbers and theory have not changed.