Many interesting (and og course correct) things has been said in this group of topics regarding picture sharpness and the depth of field.

I wish to share four examples with you, now that I have an SLR camera with lenses with a rather small minimum aperture opening.

I made four photos, all with the same focal length and the same focus piont. Only the aperture is changed, thereof also the shutter opening time. Canon EF 28-200mm f3,5-5,6 at approx 100 mm focal length.
No modifications to the photos, except the size, reduced to 640 pixels width.

At the biggest opening, f5,6:


At aperture f8:



At aperture f16:


And finally at the smallest opening f32:


Good luck!

Hi Svein, Absolutely correct!
Nice set of experiments demonstrating a basic principle.
I like the fact you used "available light", it is much more natural than Flash
Of course you picked a loco in "photographic colours" a little trick that facilitates good contrast...

I like the height you choosed, rather than the "helicopter" view we see just too often
For model RR pictures, a little bean bag on which to rest the camera safely is a big help.
It will also help keeping the subject straight (your pics are slightly tilted)
Use your timer our a remote control to release, this way you'll avoid shaking the camera on long exposures.(I use ISO 100 consistently on model RR photography, which means sometimes you have exposure times of several seconds))
One last suggestion, try to place a white cardboard piece in front of the loco and make it act as a reflector to add some contrast on the front and reveal more details.
With some "trial and error" you discover how much more details can be revealed.
Great job in any case!
Cheers

Hi Pietro

It's no only the aperture.
Other things, like the type of lens, have influence on the result too. A wide angle lens has more depth than a telelens. Fokal distance is a factor too. Distance from the camera to the subject.

Compact cameras have a smaller chip and mostly a wider angle, which allows very short focal lengths.

Svein,
This last picture is simply perfect...

Thanks for the kind comments, friend.

It's more on my website [:I]