Maximum depth of field

[Herlev DK]

Arrgggghhh I just don’t get it :-(

Okay here is one more example (of my logic…)

Okay I want to take a picture of 2 persons, one standing 2 meters behind the other.
I want to have both in focus and the background blurred.

Now using a DSLR with the 1.6 FOV, we adjust the focal length and aperture, until we get the desired DOF.

Now without adjusting the lens, we put the lens on a FF SLR, and shoot the same photo.

The DOF will in both cases be 2 meters, only difference is that the photo from FF camera has much more space around the to persons due to the wider FOV.

But in order to get the same framing in the photos, you would have to zoom in with the FF camera, and then the focal length is not the same, and of cause the DOF will then change.

Br. Karsten

 

[Peter G]

Arrgggghhh I just don?t get it :-(

Okay here is one more example (of my logic?)

Okay I want to take a picture of 2 persons, one standing 2 meters
behind the other.
I want to have both in focus and the background blurred.

Now using a DSLR with the 1.6 FOV, we adjust the focal length and
aperture, until we get the desired DOF.
Now without adjusting the lens, we put the lens on a FF SLR, and
shoot the same photo.
The DOF will in both cases be 2 meters, only difference is that the
photo from FF camera has much more space around the to persons due
to the wider FOV.

But in order to get the same framing in the photos, you would have
to zoom in with the FF camera, and then the focal length is not the
same, and of cause the DOF will then change.

Yes you have it. When taking pictures with different sized sensors/film you will need to change the focal length to equalize the FOV.

When you do that you alter the DOF, luckily that difference is Exactly equal to the focal lenght multiplier between the cameras.

Peter

 

[Forrest41926]

Nice shot, what software do you use for the frame?

Thanks.

The frames are Photoshop layers with shadow and bevel effects.

 

[hm]

The DOF will in both cases be 2 meters, only difference is that the
photo from FF camera has much more space around the to persons due
to the wider FOV.

You haven't made a print yet, so you don't know what your depth of field is. If you're planning on making a tiny wallet-size print, then everything will appear in focus; if you're planning on printing it huge and viewing it from up-close, then very little will appear in focus. Enlargement matters.

DOF depends on: focal length, subject distance, aperture, and "circle of confusion" (which depends on target print resolution, print viewing distance, and enlargement).

In your experiment, an identical image is projected by the lens onto the sensor plane, though the 300D sensor cuts out a smaller rectangle from this lens image than the 1Ds does. So you may be tempted to say that DOF is the same. But you haven't made a print yet. If you make 8x10 prints of each image, with no cropping, then you will have enlarged your 300D image 1.6x more than the 1Ds image. So the out of focus blur on the sensor will have been enlarged more, making it more apparent, reducing the depth of field (you might try to think of this as "each out of focus blur represents a larger fraction of the smaller sensor frame size, and is thus more visible in the final output"). If, for some reason, you made the 300d image into a 1.6x smaller print, then that print would look identical to the "middle" of the 1Ds print, and DOF would be identical in that portion.

Similarly, if you crop the 1Ds image to match the 300d image, then you'll have identical depth of field, as you'll effectively be enlarging each image by the same amount to reach the same print size.

But this is not a typical comparison, you'll ordinarily adjust either focal length or subject distance to achieve identical framing, and this will increase depth of field by a far larger amount than the reduce enlargement will decrease it, yielding greater depth of field on the 300D.
-harry

 

[Steven Noyes]

Many things enter in to DOF calculations. One of the items that many people forget is the print size. The DOF on a [perfect tack sharp] 4X6 print is greater than the SAME EXACT print at 16X20.

So items that were sharp at 4X6 might look somewhat OOF when rinted at 16X20.

Steven

--
---
New and Updated!!!
http://www.pbase.com/snoyes/a_study_in_light

 

[Forrest41926]

... are hideous.

Thanks. Do you mean some of the colors ( I'd have to agree, actually ) or the frames themselves?

 

[psd250]

Not to be mean, but the colros and the frames. If you intended to do a vistorian style frame as seen in new England coutry cottages, then you suceeded, other than that I feel they are overused.

A simple frame would do. Eever since people discovered ebevels and drop shadows in photoshop I have seen those efefcts used to death.

Sorry for the outburst, but I have seen this types fo frames used so much I just cracked under the pressure.

... are hideous.

Thanks. Do you mean some of the colors ( I'd have to agree,
actually ) or the frames themselves?

 

[Forrest41926]

Sorry for the outburst, but I have seen this types fo frames used
so much I just cracked under the pressure.

No need to apologize; I think we can chalk this up to constructive criticism, which is pretty much always appreciated. I wasn't being sarcastic when I said I agree if you mean the colors; it's one thing to photograph a scene, but quite another to pick complementary frame colors. That takes some learning ... and I need to go back and fix a lot of 'em. Probably make the frames smaller in relation to the photos, too, but at the end of the day I like the effect, so I'm going to continue to use it. But hopefully improve it a little, too.

 

[Sam Berry]

Forrect, that has to be one of the best responses to criticism I have ever seen on this forum. Impressive stuff.

Sorry for the outburst, but I have seen this types fo frames used
so much I just cracked under the pressure.

No need to apologize; I think we can chalk this up to constructive
criticism, which is pretty much always appreciated. I wasn't being
sarcastic when I said I agree if you mean the colors; it's one
thing to photograph a scene, but quite another to pick
complementary frame colors. That takes some learning ... and I
need to go back and fix a lot of 'em. Probably make the frames
smaller in relation to the photos, too, but at the end of the day I
like the effect, so I'm going to continue to use it. But hopefully
improve it a little, too.

 

[M. Mitchell]

Many things enter in to DOF calculations. One of the items that
many people forget is the print size. The DOF on a [perfect tack
sharp] 4X6 print is greater than the SAME EXACT print at 16X20.

So items that were sharp at 4X6 might look somewhat OOF when rinted
at 16X20.

Steven

--
---
New and Updated!!!
http://www.pbase.com/snoyes/a_study_in_light

When you are looking for large depth of field, there are other factors to consider. A point and shoot camera, such as the Canon S50, will give you the depth of field at F/2.8 equivalent to a 35mm camera at F/11 or F/16. Many times in order to stop down to F/16 you will need to use a high ISO or a tripod, whereas the point and shoot can be handheld and can use a noise free ISO of 50. Furthermore, lenses become diffraction limited at small apertures. So the 35mm lens at F/16 will not be as sharp as it would be at a larger aperture. Difraction cannot be corrected.

 

[Sam Berry]

Diffraction of a smaller lens happens just the same! Say a digicam has a crop factor of 3 from a DSLR. Digicam uses f/2.8, DSLR uses f/8. Digicam uses iso50, DSLR uses ISO400. DOF is the same, noise is still probably better on the DSLR and shutter time is the same. Digicam deep DOF is overrated.

Many things enter in to DOF calculations. One of the items that
many people forget is the print size. The DOF on a [perfect tack
sharp] 4X6 print is greater than the SAME EXACT print at 16X20.

So items that were sharp at 4X6 might look somewhat OOF when rinted
at 16X20.

Steven

--
---
New and Updated!!!
http://www.pbase.com/snoyes/a_study_in_light

When you are looking for large depth of field, there are other
factors to consider. A point and shoot camera, such as the Canon
S50, will give you the depth of field at F/2.8 equivalent to a
35mm camera at F/11 or F/16. Many times in order to stop down to
F/16 you will need to use a high ISO or a tripod, whereas the point
and shoot can be handheld and can use a noise free ISO of 50.
Furthermore, lenses become diffraction limited at small apertures.
So the 35mm lens at F/16 will not be as sharp as it would be at a
larger aperture. Difraction cannot be corrected.

 

[Sam Berry]

Sorry, realised you were comparing to 35mm film. Doesn't quite apply due to poor high-ISO.

Diffraction comment still applies.

Many things enter in to DOF calculations. One of the items that
many people forget is the print size. The DOF on a [perfect tack
sharp] 4X6 print is greater than the SAME EXACT print at 16X20.

So items that were sharp at 4X6 might look somewhat OOF when rinted
at 16X20.

Steven

--
---
New and Updated!!!
http://www.pbase.com/snoyes/a_study_in_light

When you are looking for large depth of field, there are other
factors to consider. A point and shoot camera, such as the Canon
S50, will give you the depth of field at F/2.8 equivalent to a
35mm camera at F/11 or F/16. Many times in order to stop down to
F/16 you will need to use a high ISO or a tripod, whereas the point
and shoot can be handheld and can use a noise free ISO of 50.
Furthermore, lenses become diffraction limited at small apertures.
So the 35mm lens at F/16 will not be as sharp as it would be at a
larger aperture. Difraction cannot be corrected.

 

[Forrest41926]

Forrect, that has to be one of the best responses to criticism I
have ever seen on this forum. Impressive stuff.

Thanks, Sam!!

I meant what I said; I sure as hell wasn't born knowing everything, but I'd like to at least try to learn it all...! Besides, he really does have a point, about some of the frame colors being bad. My girlfriend was an art major ( she's a painter ), so I'm improving on this end.

 

[hm]

Digicam deep DOF is overrated.

The way to think of it is that deep DOF is achievable on smaller formats at faster shutter speeds (assuming same ISO). The same DOF can always be achieved on smaller and larger formats, but the larger formats will require slower "f-numbers" and thus longer shutter speeds to achieve them.

As you point out, diffraction isn't much of an issue, as you'll get roughly the same diffraction for roughly the same DOF on both small and large formats, but those "levels" of DOF and diffraction will just be seen at larger "f-numbers" (i.e. wider apertures) on the smaller formats.

The "advantage" of wide DOF for small formats is tangible, and it occurs when you're in need of wide DOF along with fast shutter speeds, namely when hand-holding. If you're using a tripod and willing to use slow shutter speeds (i.e. you're not worried about the subject itself moving), then the difference isn't very significant.
-harry

 

[Sam Berry]

What I was saying is that if the ISO can be boosted to the same extent as the lens is stopped down then there is no shutter speed advantage. With a DSLR this is the case. ISO 50 corresponds well with 10D ISO 400, for example. Here you lose the small-sensor advantage.

Digicam deep DOF is overrated.

The way to think of it is that deep DOF is achievable on smaller
formats at faster shutter speeds (assuming same ISO). The same DOF
can always be achieved on smaller and larger formats, but the
larger formats will require slower "f-numbers" and thus longer
shutter speeds to achieve them.
As you point out, diffraction isn't much of an issue, as you'll get
roughly the same diffraction for roughly the same DOF on both small
and large formats, but those "levels" of DOF and diffraction will
just be seen at larger "f-numbers" (i.e. wider apertures) on the
smaller formats.

The "advantage" of wide DOF for small formats is tangible, and it
occurs when you're in need of wide DOF along with fast shutter
speeds, namely when hand-holding. If you're using a tripod and
willing to use slow shutter speeds (i.e. you're not worried about
the subject itself moving), then the difference isn't very
significant.
-harry

 

[GreyCard]

Hmmm not sure that's right. as I understand it, the bigger the
sensor / film size the less DoF. So you'll get more DoF with a 10D
/ 300D than with full frame 35mm, and more DoF with 35mm than with
Medium format etc. etc.

I think that what I said is correct provided that the same focal length is used for the different sensor (or film) sizes.

However, if you want to keep the same field of view with a smaller sensor, then you have to use a shorter focal length, and that produces greater depth of field. (As in compact digital cameras, where the shortest focal length of about 7.2 mm gives around the same field of view as a 38 mm lens on a 35 mm camera or a 28mm lens on a 10D/300D.)

[In mathematical terms, the explanation is that the hyperfocal distance for a given f-number is proportional to the square of the focal length f and inversely proportional to the diameter d of the circle of confusion. So, reducing f has more of an effect than reducing d, which is basically proportional to sensor size.]

--
Neil Thomas
http://www.pbase.com/neilthomas_bham

 

[Kbone]

...just fine. Just my opinion.
-Kevin