Techie question for the gurus

[ChrisN]

OK - techie question for the gurus. I understand crop factor and how the smaller sensor on most DSLRs affects field of view. What impact does the smaller sensor have on the depth of field? Is the DOF scale on my manual lenses still accurate for a given aperture, or does the smaller sensor give me a bit more DOF?

[GeneW]

DOF doesn't change. A 50mm lens looks like an 80mm after the crop factor, but retains the DOF of a 50mm, and so on up and down the line. Of course DOF is also affected by distance to subject and that tends to be a little different when using an APS-size sensor.

Gene

[JohnL]

One further consideration is that you tend to enlarge from APS by a greater factor than you would need to from film or from a "full-frame" sensor. Thus you might consider a smaller circle of confusion to be appropriate, to get the same resolution on the final print.

[ChrisN]

Ah - thank you. That's a good point John. In practice I guess this doesn't make much real difference, looking at small prints and at images on pretty average monitors, but it's always interesting to argue the theory.