ioannis
Veteran Member
Amen
--
Yiannis
'We don't take pictures with our cameras,' Newman once said. 'We take them with our hearts and we take them with our minds, and the camera is nothing more than a tool.'
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How does sensor size produce a shallower DOF?...
- Thread starter EOSMan
- Start date
Yiannis
'We don't take pictures with our cameras,' Newman once said. 'We take them with our hearts and we take them with our minds, and the camera is nothing more than a tool.'
ioannis
Veteran Member
DOF calculator says:
20D, 85mm f/2.8, 10ft, DOF=0.44ft
FF, 135mm f/2.8, 10ft, DOF=0.27ft
In practice this comparison only makes sense for the same FOV. The above numbers are for real lenses, can be attained by using prime lenses, which removes zoom focal length inconsistencies and is visible by eye, and show exactly what so many people term the "3D effect".
This is the best answer I ve read here:
Yiannis
'We don't take pictures with our cameras,' Newman once said. 'We take them with our hearts and we take them with our minds, and the camera is nothing more than a tool.'
20D, 85mm f/2.8, 10ft, DOF=0.44ft
FF, 135mm f/2.8, 10ft, DOF=0.27ft
In practice this comparison only makes sense for the same FOV. The above numbers are for real lenses, can be attained by using prime lenses, which removes zoom focal length inconsistencies and is visible by eye, and show exactly what so many people term the "3D effect".
This is the best answer I ve read here:
--The problem is that in practice in order to frame a shot in a
similar way with two cameras, one with the larger and one with the
smaller sensor, you have to either move further away with the
larger sensor or use a longer FF lens when using the larger sensor
camera.
The tricky bit is that the change in the DOF effected by the sensor
is linear while the change effected by the distance or lens focal
length is expodential. As a result, the effect of the sensor size
is lost in the larger change attributable to the focal length or
distance.
So as a practical matter you may not notice the sensor size. People
think consumer cameras produce very large DOF -- and this is true.
But that is due to the very short focal length lenses being used
and despite the small sensors, not because of them.
I understand aperture size, subject to camera distance and focal
length and I understand that all of these change compared to APC
size sensor in order to get the same FOV. But how does the size of
the sensor contribute?
Thanks
--
EOSMan (got print button?)
http://www.pbase.com/eosman
Yiannis
'We don't take pictures with our cameras,' Newman once said. 'We take them with our hearts and we take them with our minds, and the camera is nothing more than a tool.'
What? You can't frame the same subject using the same lens the same way on an APS-C camera that you can on a full frame camera. Period. You either have to use a shorter lens or increase your distance to the subject.No need to back up.
I'm pretty sure the origial question was "How does sensor size produce a shallower DOF?" which has no mention of film or lens properties.The question was whether film affects lens properties.
--
Whoever said 'a picture is worth a thousand words' was a cheapskate.
http://www.pbase.com/dot_borg
vor
Leading Member
This is right. To see this for yourself, do the following experiment: take an image with four times the resolution as your screen, one that has both in-focus and out-of-focus areas with a smooth transition in between. Viewing it full-screen, take note of the DOF on that image. Then, crop out a section within it that is the size of exactly the resolution of the screen, and make sure the crop includes the in-focus and out-of-focus areas previously mentioned (at least a representative sample). Make this crop full-screen. Now, compare the two. There will be some areas that appear out of focus in the crop, but that appeared in focus in the full-size image.
The key here is the final "viewing medium" (it need not be a print) being the same size for both, and keeping the subject distance and focal length constant. The crop here corresponds to a smaller sensor, and the full-screen image to a larger sensor. The pixel densities of the two sensors need not be the same, as long as they are both high enough to produce clearly in-focus and out-of-focus areas when the image is in the final viewing medium.
Of course, this exercise is somewhat artificial, as (in my experience) we tend to go for the framing and perspective we desire, and obtain lenses in the focal length needed in order to achieve this given the size of the sensor in the camera we're using. In that case, given the same f/ratio in the aperture of the lens, the larger sensor will give the shallower DOF. But that point has been discussed a-plenty elsewhere.
Happy shooting,
Victor
The key here is the final "viewing medium" (it need not be a print) being the same size for both, and keeping the subject distance and focal length constant. The crop here corresponds to a smaller sensor, and the full-screen image to a larger sensor. The pixel densities of the two sensors need not be the same, as long as they are both high enough to produce clearly in-focus and out-of-focus areas when the image is in the final viewing medium.
Of course, this exercise is somewhat artificial, as (in my experience) we tend to go for the framing and perspective we desire, and obtain lenses in the focal length needed in order to achieve this given the size of the sensor in the camera we're using. In that case, given the same f/ratio in the aperture of the lens, the larger sensor will give the shallower DOF. But that point has been discussed a-plenty elsewhere.
Happy shooting,
Victor
More enlargement ratio means smaller CoC for the same blur circle
in the final print and that means less DOF.
You heard right. You get less DOF with smaller sensors. It's a
linear relationship.
The reason the prevailing wisdom is the opposite of that is the
basic assumption used - constant framing. For constant framing,
you need to use a shorter focal length on the smaller sensors.
Shorter focal lengths have more DOF and the relationship is (kind
of) quadratic. That means it cancels out the linear of the
sensor-size term and reverses the effect so that, with constant
framing, you get more DOF with smaller sensors, and the effect is
(roughly) linear.
The "kind of" and "roughly" above are because the effect is only as
described for subject distance
not true, then the effect is non-linear.
--
Lee Jay
(see profile for equipment)
Those are all wrong. You can't enlarge one more than the other in a valid comparison. Brought to you by the same people who believe that digital zoom is the same as optical zoom.Whatever. As I posted above, these are from the exact equationsAnd if I enlarge a cropper's image to 10 feet by 15 feet then cut
out a 4 x 6 inch print? You can't compare at different quality
levels because you can get any result you want.
for DOF. Do you not believe this or something?
Using digital zoom. Digital zoom is not optical zoom. The full frame FOV can however be cropped to maintain a constant enlargement size at a constant quality level. That is the how you compare at identical film quality levels.They smaller CoC is caused by the increased enlargement.
Only if you believe digital zoom is the equivlent of optical zoom. Most professional photographers don't.And that's
why smaller sensors have less DOF at the same focal length -
smaller CoC.
5D, 100mm, f2.8, 10 feet, DOF = 0.5 feet
20D, 100mm, f2.8, 10 feet, DOF = 0.32 feet
Pro 1, 100mm, f2.8, 10 feet, DOF = 0.13 feet
S3, 100mm, f2.8, 10 feet, DOF = 0.08 feet
From: http://dofmaster.com/dofjs.html
That is all there is to it. Most professionals would "duh" right back at you for thinking that digital zoom is the equivalent of optical zoom.Erm, no you can't. The same lens, at the same distance on APS andNo need to back up. You can always use the same lens at the same
distance to produce an APS negative of the same quality from a full
frame negative. Whether backing up or changing focal length or
comparing at different quality levels might affect lens properties
is a different question. The question was whether film affects lens
properties.
35mm means that one of the two is incorrectly framed. If it's the
APS camera that is incorrectly framed then you've lost the edges of
the scene forever and nothing can bring them back. If it's the 35mm
camera that is incorrectly framed then all you are saying is that a
35mm frame cropped to 1.6 looks just like a 1.6 crop frame (DUH!).
dzDOF is very simply about what appears sharp in a standard sized
print (by convention this is 8x10"). If you crop a frame then you
need to enlarge it more to reach the standard print size.
The enlargement size is the same when you crop the film to APS.This
enlargement reduces apparent DOF. On the other hand to maintain a
constant field of view (FOV) you need a shorter focal length lens,
which increases DOF. This second effect is stronger than the first
so crop cameras end up with more DOF for a constant FOV.
People who talk about cutting the edges off of a piece of film or a
print seem to forget about the constant print size part of the
equation (and sometimes even the framing). If in doubt forget the
mind experements and make some actual prints. It doesn't take too
long to figure out what is right providing you stick to a contant
print size.
Scissors.What? You can't frame the same subject using the same lens the sameNo need to back up.
way on an APS-C camera that you can on a full frame camera. Period.
Or use scissors. You don't think digital zoom is optical zoom too do you?You either have to use a shorter lens or increase your distance to
the subject.
The answer is film doesn't affect the lens.I'm pretty sure the origial question was "How does sensor sizeThe question was whether film affects lens properties.
produce a shallower DOF?" which has no mention of film or lens
properties.
They all have the same final size (8x10). The increased enlargement is caused by having to enlarge more when you start with a smaller original.Those are all wrong. You can't enlarge one more than the other inWhatever. As I posted above, these are from the exact equations
for DOF. Do you not believe this or something?
a valid comparison. Brought to you by the same people who believe
that digital zoom is the same as optical zoom.
Cropping = digital zoom. These comparisons (from DOF master) are from the full-frames of each image. My crops are just that - crops. Cropping is just like using a smaller sensor as long as you have enough pixels to resolve the CoC which you do in this case.Using digital zoom. Digital zoom is not optical zoom. The fullThey smaller CoC is caused by the increased enlargement.
frame FOV can however be cropped to maintain a constant enlargement
size at a constant quality level. That is the how you compare at
identical film quality levels.
Lot's of other people in this thread have confirmed that smaller sensors have smaller DOF at the same focal lengths and f-stops. That's what the equations say and that's what the optical evidence says. It's the truth. If you don't want to believe that, then that's your choice. But the rest of us will still continue to tell the truth to those who ask like the OP.
--
Lee Jay
(see profile for equipment)
Really? Please explain how cropping a piece of full frame film to APS size makes it "lower quality" than APS film.DUH again! By definition whenever you crop you lose quality.
Full frame cropped to APS is the same enlargement size. But digital zoom is not optical zoom.on viewing the same sized print at the same distance. If you want
to define a new concept based in part on equivalent image quality,
go ahead but call it something else so others will not be confused.
Roger Krueger
Veteran Member
Or if you change distance. Changing lens and/or changing distance are the only ways to use the entire image and have the same composition.Only if you change lenses.you take the same picture (exactly the same framing!) with a FF and
a crop camera at the same aperture? I think there will be less DOF
with the FF, right?
Sure, if you have wildly different lenses, but sticking to similar fields of view the FF will always have less DOF.Changing lenses on one but not the
other can produce any result you want on DOF.
You can throw half the pixels away without affecting quality? Yeah, right.There is no need to change lenses. Full frame film can be cropped
to APS size without affecting the quality of the final enlargement
or the lens.
Sure, there is NO difference between shooting a crop sensor and cropping from a larger sensor, assuming they have the same pixel pitch. But if you're happy with that low a pixel count, sell your FF camera and buy a 300d.
Last time I checked scissors didn't work on a CMOS or CCD sensor.Scissors.What? You can't frame the same subject using the same lens the sameNo need to back up.
way on an APS-C camera that you can on a full frame camera. Period.
See above. Also, I don't believe any DSLRs have digital zoom.Or use scissors. You don't think digital zoom is optical zoom tooYou either have to use a shorter lens or increase your distance to
the subject.
do you?
The answer is that your focal length and focus distance DO affect depth of field.The answer is film doesn't affect the lens.I'm pretty sure the origial question was "How does sensor sizeThe question was whether film affects lens properties.
produce a shallower DOF?" which has no mention of film or lens
properties.
--
Whoever said 'a picture is worth a thousand words' was a cheapskate.
http://www.pbase.com/dot_borg
That is digital zoom. Starting with a crop and enlarging it. Stick to optical zoom for a valid comparision. Crop to APS to equalize FOV and enlargement size.They all have the same final size (8x10). The increasedThose are all wrong. You can't enlarge one more than the other inWhatever. As I posted above, these are from the exact equations
for DOF. Do you not believe this or something?
a valid comparison. Brought to you by the same people who believe
that digital zoom is the same as optical zoom.
enlargement is caused by having to enlarge more when you start with
a smaller original.
APS film doesn't use sensors but the same optics exist for digital.Cropping = digital zoom. These comparisons (from DOF master) areUsing digital zoom. Digital zoom is not optical zoom. The fullThey smaller CoC is caused by the increased enlargement.
frame FOV can however be cropped to maintain a constant enlargement
size at a constant quality level. That is the how you compare at
identical film quality levels.
from the full-frames of each image. My crops are just that -
crops. Cropping is just like using a smaller sensor as long as you
have enough pixels to resolve the CoC which you do in this case.
That is incorrect. Film size does not affect optics.Lot's of other people in this thread have confirmed that smaller
sensors have smaller DOF at the same focal lengths and f-stops.
The equaltions assume that digital zoom is the same as optical zoom which is wrong. If you equate digital and optical zoom as the same than you can get any DOF relationship you wish.That's what the equations say and that's what the optical evidence
says. It's the truth. If you don't want to believe that, then
that's your choice. But the rest of us will still continue to tell
the truth to those who ask like the OP.
Enlarge the full frame picture to 10 feet by 15 feet then crop a 4 x 6 inch photograph from the middle. Now you would have to say that the full frame has lower DOF versus APS. Unless you first accept that digital zoom isn't free.
You are confused. We're talking about 4 different cameras, all with different sensor sizes. There's no digital zoom going on at all.That is digital zoom. Starting with a crop and enlarging it.They all have the same final size (8x10). The increased
enlargement is caused by having to enlarge more when you start with
a smaller original.
Stick to optical zoom for a valid comparision. Crop to APS to
equalize FOV and enlargement size.
Is there a language barrier here or something?APS film doesn't use sensors but the same optics exist for digital.Cropping = digital zoom. These comparisons (from DOF master) are
from the full-frames of each image. My crops are just that -
crops. Cropping is just like using a smaller sensor as long as you
have enough pixels to resolve the CoC which you do in this case.
No, but film size does affect depth-of-field.That is incorrect. Film size does not affect optics.Lot's of other people in this thread have confirmed that smaller
sensors have smaller DOF at the same focal lengths and f-stops.
No the equations assume no such thing. You are confused again.The equaltions assume that digital zoom is the same as optical zoomThat's what the equations say and that's what the optical evidence
says. It's the truth. If you don't want to believe that, then
that's your choice. But the rest of us will still continue to tell
the truth to those who ask like the OP.
which is wrong. If you equate digital and optical zoom as the same
than you can get any DOF relationship you wish.
Did you read about how there have to be enough pixels to resolve the CoC or didn't you?Enlarge the full frame picture to 10 feet by 15 feet then crop a 4
x 6 inch photograph from the middle. Now you would have to say
that the full frame has lower DOF versus APS. Unless you first
accept that digital zoom isn't free.
--
Lee Jay
(see profile for equipment)
Snip the print.Last time I checked scissors didn't work on a CMOS or CCD sensor.Scissors.What? You can't frame the same subject using the same lens the sameNo need to back up.
way on an APS-C camera that you can on a full frame camera. Period.
Heard of the Nikon D2X? Does its lens have lower DOF compared to itself? It has digital zoom and you can print that crop any size you wish.
Every dSLR with less than a FF sensor.See above. Also, I don't believe any DSLRs have digital zoom.Or use scissors. You don't think digital zoom is optical zoom tooYou either have to use a shorter lens or increase your distance to
the subject.
do you?
Only if you first believe that digital zoom is optical zoom. The optically correct way to compare is to stick to optical zoom. That is crop to APS instead of vice versa.The answer is that your focal length and focus distance DO affectThe answer is film doesn't affect the lens.I'm pretty sure the origial question was "How does sensor sizeThe question was whether film affects lens properties.
produce a shallower DOF?" which has no mention of film or lens
properties.
depth of field.
No...digital zoom means cropping from an existing sensor and then interpolating up. A smaller sensor is just a smaller format.Every dSLR with less than a FF sensor.See above. Also, I don't believe any DSLRs have digital zoom.
--
Lee Jay
(see profile for equipment)
Scissors.Or if you change distance. Changing lens and/or changing distanceOnly if you change lenses.you take the same picture (exactly the same framing!) with a FF and
a crop camera at the same aperture? I think there will be less DOF
with the FF, right?
are the only ways to use the entire image and have the same
composition.
The FF always has an exact APS image within it.Sure, if you have wildly different lenses, but sticking to similarChanging lenses on one but not the
other can produce any result you want on DOF.
fields of view the FF will always have less DOF.
That is right. APS is a smaller format which means it uses less film area. Cropping FF film to APS size equalizes image quality. You are left with the exact APS negative.You can throw half the pixels away without affecting quality? Yeah,There is no need to change lenses. Full frame film can be cropped
to APS size without affecting the quality of the final enlargement
or the lens.
right.
A FF camera might have twice the pixel density as the APS camera. You are confusing variables. Reference film and you will understand why the format does not affect lens properties.Sure, there is NO difference between shooting a crop sensor and
cropping from a larger sensor, assuming they have the same pixel
pitch. But if you're happy with that low a pixel count, sell your
FF camera and buy a 300d.
You can't introduce digital zoom into the equation as if it has no ill affect. If you do then you can get any DOF result you wish from either format.
Okay...A FF camera might have twice the pixel density as the APS camera.
You are confusing variables. Reference film and you will
understand why the format does not affect lens properties.
8x10 film, 100mm, f2.8, 10 feet, DOF = 3.43 feet
4x5 film, 100mm, f2.8, 10 feet, DOF = 1.68 feet
6x4.5 film, 100mm, f2.8, 10 feet, DOF = 0.75 feet
35mm film, 100mm, f2.8, 10 feet, DOF = 0.5 feet
APS film, 100mm, f2.8, 10 feet, DOF = 0.42 feet
Happy?
--
Lee Jay
(see profile for equipment)
Interpolating up wouldn't change anything. Every dSLR with a crop factor uses digital zoom. Unless you always print smaller than you really want to by the crop factor.No...digital zoom means cropping from an existing sensor and thenEvery dSLR with less than a FF sensor.See above. Also, I don't believe any DSLRs have digital zoom.
interpolating up. A smaller sensor is just a smaller format.
The D2X even has selectable levels of digital zoom on top of the built-in crop factor. Do you contend that its lens has two DOFs simultaneously?
No matter how much I snip a 30D print it just won't be the same as a 5D.Snip the print.Last time I checked scissors didn't work on a CMOS or CCD sensor.
Hurray for Nikon.Heard of the Nikon D2X? Does its lens have lower DOF compared to
itself? It has digital zoom and you can print that crop any size
you wish.
Except they have more photo-sites per millimeter, so that's not true either.Every dSLR with less than a FF sensor.Also, I don't believe any DSLRs have digital zoom.
I don't know too many people who bought a full frame DSLR just so they could crop all their images to APS-C proportions. That sort of defeats the benefit of full-frame, don't you think?Only if you first believe that digital zoom is optical zoom. TheThe answer is that your focal length and focus distance DO affect
depth of field.
optically correct way to compare is to stick to optical zoom. That
is crop to APS instead of vice versa.
--
Whoever said 'a picture is worth a thousand words' was a cheapskate.
http://www.pbase.com/dot_borg
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