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DOF and focal length is a common misconception.
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I hold my hand up to this.
As members are on during the day and without many new posts, I was posting this thread was to suggest to members that were on, that using focal lengths other than the most obvious would have an impact on the final image. Almost I soon came on I was under pressure from the ' management ' as a trip to the shops had been scheduled and I was holding things up...... priorities, priorities.
So if I can, with a drink in hand, ammend the topic to lens effects on perspective which was the primary thought.
Its Robs ' Gable Roofs ' that brought this to mind.
I had a lot of explaining to do to the ' Boys in Blue ' at Windsor when I was setting up to take the castle with 400mm + 2x. As the castle is set up on high ground and across the main road is also high ground level with the castle, this is where I was. I wanted to use the perspective compression of 800mm to make the road to the castle appear considerably steeper than it is. I had to prove to the boys in blue that the camera was a camera and the lens a lens etc, etc. This was years ago - would not try it today.
Saphire's ' Frozen Lake ' or Steve Randles ' Buttermere View ' both use the huge depth of field that a wide angle gives. This is really where the DOF bit came in. Take Steves, picture selective focusing and use of dof gets everything sharp.
Snappy's ' Bright Eyes ' using a 500mm lens at f5.6 has just blown the background away ( selective use of aperture ).
I have to admit to being a bit confused by some of the conversion factors shown in the exifs. Steves reads Camera - Canon EOS DIGITAL REBEL - Lens 25.0mm (35mm equivalent: 174mm). I have difficulty seeing this as an aperture of f10 at 174mm.
I have never considered dof from the image size on film before. If I wanted more dof I would use a slower film wider lens and enlarge that part of the frame. I have used bellows on a 300mm just to blast the background before now. That is what I was referring to.
Forgiven? ............
Don
PS greypoints ' Riverside flowers ' is another example of using a long lens small aperture to blow a background. Although this could have been taken with a shorter lens the effect on out of focus area would not be the same. If you return to the tutorial and look at the tower in the background it has a far softer blurr at 400 than the 200 and through to 50mm. It is a good example if you ignore the blurr, of telephoto perspective compression effect. Compare the tower to subject through all focal lengths imagining they were both in focus.
PPS I must be nuts being here at this time of night. Trying to catch up on the Gallery.