Comparative DOF, sensor size and lenses...

[Duke]

Barry Green posted an excellent article that gives you a much better idea how cameras will compare as far as DOF goes with different camera sensors and different lenses.

In essence, an EX1 would have to be 3 1/2 stops (1.4 vs 4.8) wider to match a 7D in DOF.
An HV30 would only have to be 1 stop wider to match the EX1, but would need 4 1/2 stops to match a 7D (1.8 vs 8).

I might add that a standard full F-stop scale is as follows:
1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22 - 32 - 45

A half F-stop scale is:
1.4 - 1.7 - 2 - 2.4 - 2.8 - 3.3 - 4 - 4.8 - 5.6 - 6.7 - 8 - 9.5 - 11 - 13 - 16 - 19 - 22

The full article is here:
http://www.dvxuser.com/V6/showthread.php?p=1803716#post1803716

The parts I found most useful:
"Here are the iris differences I derived, to get the same DOF at the same field of view at the same subject distance, on different-sized sensors:

A 1/4" sensor would need to be 3/4 of a stop more open to match a
1/3" sensor, which would need to be 1 stop more open to match a
1/2" sensor, which would need to be 2/3 of a stop more open to match a
2/3" sensor, which would need to be 2 1/4 stops more open to match a
4/3 sensor, which would need to be 1/2 stop more open to match an
APS-C sensor, which would need to be 1 1/2 stops more open to match a
Full-frame sensor.


Okay, so... put another way, here are some tables based on each camera size, showing the difference in stops you'd have to use in order to get them to look visually equvalent:

For a 1/4" camera to match to
1/3" - open up 3/4 of a stop
1/2" - open up 1 3/4 stops
2/3" - open up 2 1/2 stops
4/3 or GH1 - open up 4 3/4 stops
APS-C or 7D - open up 5 1/4 stops
Full frame - open up 6 3/4 stops

For a 1/3" camera to match to
1/2" - open up 1 stop
2/3" - open up 1 2/3 stops
4/3 or GH1 - open up 4 stops
APS-C or 7D - open up 4 1/2 stops
Full frame - open up 6 stops

For a 1/2" camera to match to
2/3" - open up 2/3 of a stop
4/3 or GH1 - open up 3 stops
APS-C or 7D - open up 3 1/2 stops
Full frame - open up 5 stops

For a 2/3" camera to match to
4/3 or GH1 - open up 2 1/4 stops
APS-C or 7D - open up 2 3/4 stops
Full frame - open up 4 1/4 stops

For a movie camera or APS-C-sized camera like the Canon 7D, to match to
a full frame - open up 2 stops"

[dcloud]

i guess 1/3 to 1/2 idoesnt have THAT much difference at all
as well as 4/3 to aps-c

[Duke]

And not that much real difference in the 2/3" scarlet, which is what I suspected all along {despite Halsu's arguments to the contrary.} For example:

For a 1/3" camera to match to 2/3" - open up 1 2/3 stops.

That isn't much difference. The other factor is the length of the lens. I've always thought that with only an 8x zoom the fixed scarlet isn't going to beat an A1 in DOF with a 20x zoom.

In fact, my rough calculation before was that a Scarlet at full zoom is about the same as an A1 at 3/4 zoom (16x) at the same aperture. Or at the same zoom its 1 2/3 stops different albeit with a change in the FOV. Not a huge difference.

Of course 1/3" sensors with only 10-14x zoom will be beaten in DOF control by the Scarlet all the time.

Consider too that the A1 opens to f1.6 while the Scarlet fixed is rumored to T3, about f2.8. Thats about 1.5 stops different. That means the A1 should have more DOF control at the far end of the zoom, if you have the room to back up. :hv20-smilie58:

Resolution should be another matter so the Red fanbois don't need to get out the torches and wooden stakes. :hv20-smilie84:

[dcloud]

pixel/sharpness is the advantage

[Duke]

Yep, the resolution should provide more details with the Scarlet. However, can you think of one movie where the level of detail told the story, or made you think someone was worth paying attention to, or that the characters are in love.

That's what DOF control can help you do, help you tell the story by focusing the audience on certain things, or to indicate that the characters are concentrating on each other.