Depth of field difference between APS-C and full frame

I'm taking a class that deals primarily with developing and printing b&w
film so I pulled out my old Minolta SLR. Since I've been shooting
digital exclusively for the last 3 years I just want to get my head
around the difference in depth of field with the 35mm SLR.

At a given focal length and aperture (and ISO) will the DOF be less on
the 35mm?

Greg
--
Ticketmaster and Ticketweb suck, but everyone knows that:
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Dethink to survive - Mclusky

"G.T." wrote in message
...
I'm taking a class that deals primarily with developing and printing
b&w film so I pulled out my old Minolta SLR. Since I've been
shooting digital exclusively for the last 3 years I just want to get
my head around the difference in depth of field with the 35mm SLR.

At a given focal length and aperture (and ISO) will the DOF be less
on the 35mm?

Depth of Field depend on:
1.The focal length of the lens
2.The aperture
3.The distance from film plane to subject

The size of the film or CMOS is of no consequence.



Greg
--
Ticketmaster and Ticketweb suck, but everyone knows that:
http://www.ticketmastersucks.org

Dethink to survive - Mclusky

G.T. wrote:

I'm taking a class that deals primarily with developing and printing b&w
film so I pulled out my old Minolta SLR. Since I've been shooting
digital exclusively for the last 3 years I just want to get my head
around the difference in depth of field with the 35mm SLR.

At a given focal length and aperture (and ISO) will the DOF be less on
the 35mm?

No, it's the same but that's because of your wording. For the same
*field of view* at the same print size the DOF changes by the same 1.5x
(.66x) factor as is used for the 35mm equivalent field of view.

At 50mm f/1.8 on full frame, to match that field of view with APS you
would zoom out to 33mm & have 1.5 times the DOF. This is the same effect
as cropping the full frame image by .66x and enlarging it so that's an
easy way to see exactly what the effect is. If you wanted the same
shallow DOF you would need a faster lens. There is a 30mm f/1.4 Sigma
for about $380 versus the typical $100 50mm f/1.8. I'm not sure how to
apply the math to the f-stop but it would require a lens even faster
than that which is not available.

OK here's a calculator:
http://www.cambridgeincolour.com/tut...h-of-field.htm

at 50mm f/1.8 focused at 3 meters
2.8m Closest distance of acceptable sharpness
3.2m Furthest distance of acceptable sharpness
0.4m Total Depth of Field

at 30mm f/1.4 focused at 3 meters (a little wider than eq. 33mm)
2.8m Closest distance of acceptable sharpness
3.3m Furthest distance of acceptable sharpness
0.5m Total Depth of Field


Here's a comparable set:

at 75mm f/2.8 focused at 3 meters
2.9m Closest distance of acceptable sharpness
3.2m Furthest distance of acceptable sharpness
0.3m Total Depth of Field

at 50mm f/1.8 focused at 3 meters (1.5 stops faster)
2.9m Closest distance of acceptable sharpness
3.1m Furthest distance of acceptable sharpness
0.3m Total Depth of Field



--
Paul Furman Photography
http://edgehill.net
Bay Natives Nursery
http://www.baynatives.com

Paul Furman wrote:
G.T. wrote:

I'm taking a class that deals primarily with developing and printing
b&w film so I pulled out my old Minolta SLR. Since I've been shooting
digital exclusively for the last 3 years I just want to get my head
around the difference in depth of field with the 35mm SLR.

At a given focal length and aperture (and ISO) will the DOF be less on
the 35mm?

No, it's the same but that's because of your wording. For the same
*field of view* at the same print size the DOF changes by the same 1.5x
(.66x) factor as is used for the 35mm equivalent field of view.

That's what I figured but just wanted to make sure I wasn't missing
anything.


At 50mm f/1.8 on full frame, to match that field of view with APS you
would zoom out to 33mm & have 1.5 times the DOF. This is the same effect
as cropping the full frame image by .66x and enlarging it so that's an
easy way to see exactly what the effect is. If you wanted the same
shallow DOF you would need a faster lens. There is a 30mm f/1.4 Sigma
for about $380 versus the typical $100 50mm f/1.8. I'm not sure how to
apply the math to the f-stop but it would require a lens even faster
than that which is not available.

OK here's a calculator:
http://www.cambridgeincolour.com/tut...h-of-field.htm

Excellent.

Greg

--
Ticketmaster and Ticketweb suck, but everyone knows that:
http://www.ticketmastersucks.org

Dethink to survive - Mclusky

"Frank Arthur" wrote in message
.. .

"G.T." wrote in message
...
I'm taking a class that deals primarily with developing and printing b&w
film so I pulled out my old Minolta SLR. Since I've been shooting
digital exclusively for the last 3 years I just want to get my head
around the difference in depth of field with the 35mm SLR.

At a given focal length and aperture (and ISO) will the DOF be less on
the 35mm?

Depth of Field depend on:
1.The focal length of the lens
2.The aperture
3.The distance from film plane to subject

The size of the film or CMOS is of no consequence.

Oh crap, some of my cameras have neither film or CMOS, how the hell are they
affected?

G.T. writes:

At a given focal length and aperture (and ISO) will the DOF be less on
the 35mm?

Take a 35mm film exposure. Trim the edges of the film with scissors so
that it is APS-C size. Did you just change the DOF?

"G.T." wrote in message ...
I'm taking a class that deals primarily with developing and printing b&w film so I pulled out my old Minolta SLR. Since I've been
shooting digital exclusively for the last 3 years I just want to get my head around the difference in depth of field with the 35mm
SLR.

At a given focal length and aperture (and ISO) will the DOF be less on the 35mm?

Hi Greg,

It depends on your reference point - in the camera or in the final print.

A lens of a given focal length and aperture will produce a image circle with the same DoF regardless of the dimensions of the media
(film/sensor) the image is projected onto. It doesn't matter whether that lens is from a tiny P&S camera or an 8*10 field camera. If
you put the latter's lens on the former's body, the DoF would be the same.

However, if you only use take a small section from the center of the theoretically available image, as happens with the APS-C
format, then you have to enlarge the image more to get the same size print. The result is reduced apparent DoF. The reduction is
somewhat more than the crop factor.

For example, a 15*10cm print from a 35mm camera with an 80mm lens @ f4 and a subject 4m from the lens will have a FoV of 1.8*1.2m
and a DoF of about 0.6m. The same 15*10cm print from a Canon 20D/30D with its 1.6 FoV crop factor (a true APS-C camera has a 1.43
FoV crop) and the same 80mm lens @ f4 and the same subject distance will have a FoV of 1.125*0.75m and a DoF of about 0.4m.

Conversely, if you use small-format camera with a wider angle lens and/or move back further, to capture the same area of scene as
you could see with the larger lens on the larger format camera, and don't change the aperture, you increase the DoF again, and that
increase is much more than the apparent loss through greater magnification.

So now, if you put a 50mm lens @ f4 on the Canon 20D/30D with subject 4m from the lens will have a FoV of 1.8*1.2m and a DoF of
about 1.0m. Alternatively, if you keep the 80mm lens @ f4 on the Canon 20D/30D and move back to 6.4m from the subject, then lens
will have a FoV of 1.8*1.2m and a DoF of about 1.0m. Note how in both cases the FoV is the same as in the first example. Note too
how changing lenses and position to capture the same FoV results in the same apparent DoF.

Cheers
--
cmyk

cmyk wrote:

"G.T." wrote in message
...

I'm taking a class that deals primarily with developing and printing
b&w film so I pulled out my old Minolta SLR. Since I've been shooting
digital exclusively for the last 3 years I just want to get my head
around the difference in depth of field with the 35mm SLR.

At a given focal length and aperture (and ISO) will the DOF be less on
the 35mm?


Hi Greg,

It depends on your reference point - in the camera or in the final print.

A lens of a given focal length and aperture will produce a image circle
with the same DoF regardless of the dimensions of the media
(film/sensor) the image is projected onto. It doesn't matter whether
that lens is from a tiny P&S camera or an 8*10 field camera. If you put
the latter's lens on the former's body, the DoF would be the same.

However, if you only use take a small section from the center of the
theoretically available image, as happens with the APS-C format, then
you have to enlarge the image more to get the same size print. The
result is reduced apparent DoF. The reduction is somewhat more than the
crop factor.

For example, a 15*10cm print from a 35mm camera with an 80mm lens @ f4
and a subject 4m from the lens will have a FoV of 1.8*1.2m and a DoF of
about 0.6m. The same 15*10cm print from a Canon 20D/30D with its 1.6 FoV
crop factor (a true APS-C camera has a 1.43 FoV crop) and the same 80mm
lens @ f4 and the same subject distance will have a FoV of 1.125*0.75m
and a DoF of about 0.4m.

Conversely, if you use small-format camera with a wider angle lens
and/or move back further, to capture the same area of scene as you could
see with the larger lens on the larger format camera, and don't change
the aperture, you increase the DoF again, and that increase is much more
than the apparent loss through greater magnification.

So now, if you put a 50mm lens @ f4 on the Canon 20D/30D with subject 4m
from the lens will have a FoV of 1.8*1.2m and a DoF of about 1.0m.
Alternatively, if you keep the 80mm lens @ f4 on the Canon 20D/30D and
move back to 6.4m from the subject, then lens will have a FoV of
1.8*1.2m and a DoF of about 1.0m. Note how in both cases the FoV is the
same as in the first example. Note too how changing lenses and position
to capture the same FoV results in the same apparent DoF.

So sticking with the 50mm f/1.8 lens, if you move it from 35mm to APS &
step back to get the same FOV, the DOF corrects itself to the same place
because of the longer distance? Of course the background 'magnification'
will change but will the actual DOF be the same like from nose to ears
in a portrait? I know that a longer lens at the same f-stop will have
shallower DOF for the same face and this is sort of the same concept.

--
Paul Furman Photography
http://edgehill.net
Bay Natives Nursery
http://www.baynatives.com

Richard J Kinch wrote:

Take a 35mm film exposure. Trim the edges of the film with scissors so
that it is APS-C size. Did you just change the DOF?

Blow the resulting 'cropped' image up to the print size you really
wanted for the composition. The DOF is shallower.

DOF scales on a lens assume approximately an 8x10 print viewed at a
normal distance for the print size.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.

On Sep 14, 9:16 am, Alan Browne
wrote:
Richard J Kinch wrote:
Take a 35mm film exposure. Trim the edges of the film with scissors so
that it is APS-C size. Did you just change the DOF?

Blow the resulting 'cropped' image up to the print size you really
wanted for the composition. The DOF is shallower.

DOF scales on a lens assume approximately an 8x10 print viewed at a
normal distance for the print size.

--
-- r.p.e.35mm user resource:http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems:http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz:http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.

SO many opinions, so many errors.