Field of depth

[Paul Engen]

(Please excuse my English.)

On many of Canons cameras, you have to multiply by 1,6 to get the focal lenght of the mounted lense.

With that in mind, you get the correct field of depth (not sure if I use the right term for this) using a 50 mm lense on a 35 mm camera (or a full format digital camera - like the EOS 1 mark II) - the distance between objects infront of each other seems to have the correct distance to each other. (With tele lense they seem closer to each other, with wide lense they seem further apart.)

THE QUESTION:
Does the 50 mm lense make the correct field of depth on all cameras (e.g. Canon 350D/XT) or do you have to calculate to find the lense which makes the "correct field of depth"? (31,25 mm x 1,6 = 50 mm)

[Paul Engen]

On many of Canons cameras, you have to multiply by 1,6 to get the focal lenght of the mounted lense.

With that in mind, you get the correct field of depth (not sure if I use the right term for this) using a 50 mm lense on a 35 mm camera (or a full format digital camera - like the EOS 1 mark II) - the distance between objects infront of each other seems to have the correct distance to each other. (With tele lense they seem closer to each other, with wide lense they seem further apart.)

THE QUESTION:
Does the 50 mm lense make the correct field of depth on all cameras (e.g. Canon 350D/XT) or do you have to calculate to find the lense which makes the "correct field of depth"? (31,25 mm x 1,6 = 50 mm)

(Please excuse my English.)

[Longwatcher]

For Depth of Field (DoF) the lens will have the same DoF at the same distance whether it is APS-C (1.6x), or full frame (FF) 35mm format. However, if you back up to get same field of view (same coverage area in image) then because you have changed distance, the DoF will be different at the point of focus.

The only difference between 1.6x, 1.3x, and FF is the field of view of the image. Because the 1.6x sensor is smaller it effectively crops the image, thus to get the same area of coverage you need to back up. This makes it seem like a telephoto lens, but nothing has really changed, your sensor is just covering a smaller area then a FF sensor would.

Hope that helps,

[Longwatcher]

For Depth of Field (DoF) the lens will have the same DoF at the same distance whether it is APS-C (1.6x), or full frame (FF) 35mm format. However, if you back up to get same field of view (same coverage area in image) then because you have changed distance, the DoF will be different at the point of focus.

The only difference between 1.6x, 1.3x, and FF is the field of view of the image. Because the 1.6x sensor is smaller it effectively crops the image, thus to get the same area of coverage you need to back up. This makes it seem like a telephoto lens, but nothing has really changed, your sensor is just covering a smaller area then a FF sensor would.

Hope that helps,

Also, please only ask the question once in the future, makes it easier on those of us who get confused easily. :)

[CyberDyneSystems]

Also;
http://photography-on-the.net/forum/showthread.php?t=45388

As the link above covers the issues involved in depth,. (of field? ;) )
And Longwatcher's reply pretty much sums up hundreds of pages of chatter in 4 economical and accurate sentences...


Let's lock these two merged threads here :)