DOF depth of field table
There is a lot of confusion about circles of confusion...predictable I suppose ! This table uses the equation from the focal encyclopedia. It shows, as a simple example, that the DOF of a 50mm lens on a 1/2 frame camera at f/1.4 is the same as that of a 100mm lens on a full frame camera at f/2.8, when both are focussed at a distance of 10metres, and for the same coc as a percentage of the frame - ie 0.2% or 1/500th. The table calculates the near and far distances around the focal distance where we reach this coc, the difference is the DOF. I use the % of the frame, since when we print our pictures out the same size, with in this example the same view, then it is that that matters, not the actual mm of the coc.
I didnt mention, but a 50mm lens on 1/2 frame gives the same field of view as 100mm on full frame.
Hopefully it will also be apparent from this that since the physical coc is larger on a larger format camera, then for the same resulting image sharpness the lens does not have to be so good - the molded plastic lens in the compact cameras are startlingly good when you consider the small sensor size, not to mention the zoom ratios achieved. CAD and CADCAM for you!
For the non-beleivers, have uploaded some test shots. Sorry for no exif on the 4/3rds shots, this is because I used a canon FD manual 50mm f/1.4 lens...bit out of my budget for a electronic one.
DOF depth of field table
There is a lot of confusion about circles of confusion...predictable I suppose ! This table uses the equation from the focal encyclopedia. It shows, as a simple example, that the DOF of a 50mm lens on a 1/2 frame camera at f/1.4 is the same as that of a 100mm lens on a full frame camera at f/2.8, when both are focussed at a distance of 10metres, and for the same coc as a percentage of the frame - ie 0.2% or 1/500th. The table calculates the near and far distances around the focal distance where we reach this coc, the difference is the DOF. I use the % of the frame, since when we print our pictures out the same size, with in this example the same view, then it is that that matters, not the actual mm of the coc.
I didnt mention, but a 50mm lens on 1/2 frame gives the same field of view as 100mm on full frame.
Hopefully it will also be apparent from this that since the physical coc is larger on a larger format camera, then for the same resulting image sharpness the lens does not have to be so good - the molded plastic lens in the compact cameras are startlingly good when you consider the small sensor size, not to mention the zoom ratios achieved. CAD and CADCAM for you!
For the non-beleivers, have uploaded some test shots. Sorry for no exif on the 4/3rds shots, this is because I used a canon FD manual 50mm f/1.4 lens...bit out of my budget for a electronic one.