more light required for large format

[andy_shand1]

i have read on more than one occasion that large format requires

greater ammounts of flash than say medium format on interiors....is

this to do with using wider lenses on smaller formats thus increasing

depth of field and thus allowing greater appetures ect ect ..or is it

just a load of *&**

[lwg]

It is because you need to use smaller apertures to get the same DOF as a smaller format - thus you need more light. If you shoot at the same aperture then obviously there will be no difference.

[andy_shand1]

thanks

[steve_levine]

Tricks of the trade: multiple pops of flash.Exposing the same sheet multiple times,flash "accumulates" allowing low WS units to be used at F22.

[jay_de_fehr]

Less effective for portraits. Thanks, Steve.

[dave schlick]

as the format gets larger (and using that formats average lens) you do loose depth of field that is in focus.. in this instance you will need more light to have the same in focus depth as with smaller formats.. if you use a 135mm lens on a 35mm cammera, and a 135 mm lens on the 4x5 then the focus depth of field, (except subject coverge on the film, will be the same.. sorry i cant explain it better.. dave..

[golliegwillie]

Also most large format lenses are not optimized for wide open use; whereas medium format lenses, because of their wide use in portraiture, are design to be used at wide apertures.