JoeBiker Loc: homebase: Houston, TX

I recently got a Nikon D3100 with a Sigma 18-250mm f/3.5-6.3 Lens. I am struggling with the focus and depth of field with it. Here is an (non-artistic, but good technical) example. A piece of paper a few feet away; Maybe a slight angle, but less than 45 degrees (and mainly on the vertical axis). Any insight as to why the Rivera can be sharp, an the "M", a few inches away, is out of focus? It doesn't seem to me that f/6 would be wide enough to cause the DoF to be that shallow.

(in case, you were curious, we were touring the Waterford factory when they were making a crystal trophy for Mariana Rivera; this was part of the pattern.)

FYI, I am traveling so my responses may be delayed.

Thanks, in advance, for your help.

Searcher Loc: Kent, England

Nikon D3100, 135mm lens @ f/6 DoF is less than 2 inches with a subject distance of 5 feet.
The sharpest parts of the image are the letters "era", everything else is outside of the DoF range.

If you have not yet seen the Dofmaster site, give it a whirl.
http://www.dofmaster.com/dofjs.html

JR1 Loc: Tavistock, Devon, UK

+1

Read this

http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

JoeBiker Loc: homebase: Houston, TX

OK, thanks to both of you for your help.

JR1 Loc: Tavistock, Devon, UK

Don't think that my reply "Read this" was blunt, being dyslexic I find posting helpful links easier

jeep_daddy Loc: Prescott AZ

Because your depth of field at 135mm f/5.6 (closest I could get to f/6 and 36 inches from subject you'd have only .35 of an inch of the subject that would be in focus. You must learn DOF (depth of field) to understand. Here's a snap shot of a DOF calculator.

JoeBiker Loc: homebase: Houston, TX

No Problem at all. I had a technical understanding of DoF, and Aperture; but this is my first real zoom lens, and I didn't realize that it would become so severe. The DoF calculator was helpful, and the tutorial explained the implications of the zoom. I now know not to use the zoom as a crutch, and to "get closer, and then get closer" (and crack up the F stop).

Thanks again (to all of you) for your help.