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DPChallenge Forums >> Tutorials >> Depth of Field for Digital Cameras- A Brief Primer
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 08/14/2002 03:18:09 PM · #1
Discussion of...
Depth of Field for Digital Cameras - A Brief Primer
by magnetic9999

* This message has been edited by the author on 8/14/2002 3:23:15 PM.
 08/14/2002 03:34:36 PM · #2
Originally posted by drewmedia:
Discussion of...
Depth of Field for Digital Cameras - A Brief Primer by magnetic9999


Good tutorial. One thing that is missing is the
impact of camera <-> subject distance on DoF

I.e., you get a whole lot less depth of field when you are doing
macro shots, vs. when the point you've focused on is say 5ft away,
at the same aperture settings


* This message has been edited by the author on 8/14/2002 3:34:06 PM.
 08/14/2002 06:47:19 PM · #3
minor thing - need to correct the spelling for aperture thoughout.
 08/14/2002 07:30:12 PM · #4
I think this tutorial should be moved up into the Camera Operation section rather than the Composition section.... thoughts?
 08/14/2002 07:40:42 PM · #5
Good addition, could I also suggest mentioning that angle of attack (often my advice) also has an impact. High angles increase the amount of shooting territory to attempt to focus on. Reducing that angle to closer to straight on helps those with less manual control. If only I had a digital camera that could go up to F68.....

Originally posted by GordonMcGregor:
Originally posted by drewmedia:
[i]Discussion of...
Depth of Field for Digital Cameras - A Brief Primer by magnetic9999


Good tutorial. One thing that is missing is the
impact of camera <-> subject distance on DoF

I.e., you get a whole lot less depth of field when you are doing
macro shots, vs. when the point you've focused on is say 5ft away,
at the same aperture settings[/i]


 08/14/2002 07:49:19 PM · #6
good points, all :)..

i always thought either spelling was acceptable .. :P

i'll add a section elaborating on that Gordon, that's a good point.

as for where it should be, on the one hand DOF is used as a compositional tool, on the other hand, it requires the ability to operate your camera to be used effectively. any further thoughts on that?

Originally posted by GordonMcGregor:
Originally posted by drewmedia:
[i]Discussion of...
Depth of Field for Digital Cameras - A Brief Primer by magnetic9999


Good tutorial. One thing that is missing is the
impact of camera <-> subject distance on DoF

I.e., you get a whole lot less depth of field when you are doing
macro shots, vs. when the point you've focused on is say 5ft away,
at the same aperture settings[/i]

 08/16/2002 05:18:38 PM · #7
Mag, there is still one point that my thick skull can't seem to allow to pass. Apeture Priority vs. Shutter Priority. I get the part about which is weighted more heavily, that's in the name, but I don't get why one version would produce a "good" image and the other would not, given the same F stop and shutter speed.
Let's spell it out. If I am in AP mode, F8 and 1/500 sec and take a shot, it looks the same to me as SP mode, F8 and 1/500 sec. What's the difference? Signed eternally confused.....
 08/17/2002 12:12:27 AM · #8
dear swashbuckler

you are absolutely right. whether you're in f/8 at 500 in A mode or f/8 at 500 in S mode, there will be no difference in the picture. the point of A and S modes are that each has potentially the same 'end', but are different 'means to getting there, depending on what the photographer is after.

For example, if you know that you want a shallow DOF, then you know you can control that by controlling the aperature. so you go to A mode and select a wide ap (small number). then you let the camera figure out what shutter speed is needed to give a correct exposure.

Similarly, you might want a lot of DOF and there's enough light, so you give the camera a small aperature and again let it select the shutter speed. Again using aperature priority.

But say, you're in a different situation where you know you're going to need a fast shutter. i.e. you're shooting bands and you don't want their to be any chance of camera shake, so you know you want to lock the shutter to 1/60 s. Then you would use Shutter priority or S mode. You choose the shutter and trust the camera to pick the aperature that again fulfills the conditions for a good exposure. If it was bright, the camera might choose a small aper (hi number) and if it was dark the cam might choose a big aper to let in more light, so the DOF would vary depending, but because your PRIORITY was the shutter speed, you used shutter priority.

so again, they can do the same things, they're just different means/tools.

hope that's a little clearer :)
 08/17/2002 12:40:07 AM · #9
Three things affect DOF, Aperature, focal lenght, and subject distance.

 08/19/2002 02:49:06 PM · #10
Mag, if you are not a teacher, you should be. The explaination was good to the extreme. Thick skull and all, I now have it! This was pretty much as I suspected, but at times, not being a total camera geek, I have my problems understanding differences when they are so similar. (No insult intended with the camera geek thing, one geek to another...)


Originally posted by magnetic9999:
dear swashbuckler

you are absolutely right. whether you're in f/8 at 500 in A mode or f/8 at 500 in S mode, there will be no difference in the picture. the point of A and S modes are that each has potentially the same 'end', but are different 'means to getting there, depending on what the photographer is after.

For example, if you know that you want a shallow DOF, then you know you can control that by controlling the aperature. so you go to A mode and select a wide ap (small number). then you let the camera figure out what shutter speed is needed to give a correct exposure.

Similarly, you might want a lot of DOF and there's enough light, so you give the camera a small aperature and again let it select the shutter speed. Again using aperature priority.

But say, you're in a different situation where you know you're going to need a fast shutter. i.e. you're shooting bands and you don't want their to be any chance of camera shake, so you know you want to lock the shutter to 1/60 s. Then you would use Shutter priority or S mode. You choose the shutter and trust the camera to pick the aperature that again fulfills the conditions for a good exposure. If it was bright, the camera might choose a small aper (hi number) and if it was dark the cam might choose a big aper to let in more light, so the DOF would vary depending, but because your PRIORITY was the shutter speed, you used shutter priority.

so again, they can do the same things, they're just different means/tools.

hope that's a little clearer :)

 08/26/2002 08:49:02 PM · #11
Thanks, Swash!! :):):):)

Originally posted by Swashbuckler:
Mag, if you are not a teacher, you should be. The explaination was good to the extreme. Thick skull and all, I now have it!

09/05/2002 05:01:00 AM · #12
Originally posted by drewmedia:
Discussion of...
Depth of Field for Digital Cameras - A Brief Primer
by magnetic9999]

My E-20 stops down to only f-11. Can the author give some literature/data references to explain why digital cameras have a depth of field 4 to 5 stops greater than 35mm cameras?

Pierce Day

* This message has been edited by an administrator (drewmedia) on 9/5/2002 10:49:14 AM - fixing bad html.
 09/05/2002 08:09:40 AM · #13
Dear Pierce Day

Please read the following article. Warning, it is fairly technical.

Depth of Field for Dcams

Best,

Kollin Bliss



Originally posted by pierceday:
Originally posted by drewmedia:
[i]Discussion of...
Depth of Field for Digital Cameras - A Brief Primer
by magnetic9999

My E-20 stops down to only f-11. Can the author give some literature/data references to explain why digital cameras have a depth of field 4 to 5 stops greater than 35mm cameras?

Pierce Day[/i]

* This message has been edited by an administrator (drewmedia) on 9/5/2002 10:49:37 AM - fixing bad html.
 09/05/2002 09:50:34 AM · #14
Originally posted by magnetic9999:
Dear Pierce Day

Please read the following article. Warning, it is fairly technical.

Depth of Field for Dcams

Best,

Thanks, Kollin.
It is a great article and makes it clear.
Maybe the manufacturers should change the f stop ingravings to reflect the real world for dummies like me..
Pierce

Kollin Bliss



Originally posted by pierceday:
[i]Originally posted by drewmedia:
[i]Discussion of...
Depth of Field for Digital Cameras - A Brief Primer
by magnetic9999

My E-20 stops down to only f-11. Can the author give some literature/data references to explain why digital cameras have a depth of field 4 to 5 stops greater than 35mm cameras?

Pierce Day[/i][/i]



* This message has been edited by an administrator (drewmedia) on 9/5/2002 10:49:58 AM - fixing bad html.
 09/05/2002 11:57:39 AM · #15
well, pierce, an aper isn't a set number. It's a ratio. an aper of 2 means that the diameter of the aper is 1/2 the focal length of the lens.

so there's no false advertising there. it's still that same ratio (and therefore, light gathering capacity) and that's what those numbers refer to, not the DOF.

on a similar note, the Olympus E-xx cameras have the actual lens focal length engraved on the barrel. It says 9-35mm. This is a case where I would actually prefer the 35mm equivalents on there (35-140mm) as my experience is more 'calibrated' to that scale. Since the numbers are sort of meaningless, I just use whatever frames the shot best through the viewfinder.

Thanks for your interest.

kollin

* This message has been edited by the author on 9/6/2002 3:30:08 AM.
 11/01/2002 08:46:53 AM · #16
On the shallow DoF theme, here's a shot I took yesterday - possibly
too shallow given the rear petals are soft, but I liked it.
11/01/2002 09:41:04 AM · #17
hey gordito : )

nice work.. setup ? details? ? ? ?

: )


Originally posted by Gordon:
On the shallow DoF theme, here's a shot I took yesterday - possibly
too shallow given the rear petals are soft, but I liked it.


 11/01/2002 09:48:49 AM · #18
Taken in the Zilker Botanical Gardens, Austin, Tx on a cold, overcast day
(which is excellent for good saturated colours)

G2, with custom white balance set (metered from a white card) and exposed
with I think a +2/3rds exposure comp. to stop the yellows going muddy.

Camera on a tripod, set-up to keep the flowers in the background to
give the 'spotted' effect of the very out of focus other blooms.

Hoya +4 macro adaptor lens on the camera, to get the zoom I needed, macro
focus set, then waited for quite a while on the wind calming down enough to get the flower sharp and not moving. Aperture as wide open as possible to blow out the background (f2.5 I think), shot in aperture priority mode. Other details I can find out later - don't have them handy.

* This message has been edited by the author on 11/1/2002 9:47:08 AM.
 11/01/2002 11:15:51 AM · #19
I have a question .. I understand , but never thought that it was for me;-) .. the importance of doing the white balance on a white card.
Is it still something that needs to be done even with the auto balance and auto everything ?

In that case Gordon, do you get more accurate colors because the white balance is adjusted on a white card, doing the settings correctly regarding the ambiant light. I am understanding correctly why to do that ?
 11/01/2002 12:08:10 PM · #20
Originally posted by lionelm:
I have a question .. I understand , but never thought that it was for me;-) .. the importance of doing the white balance on a white card.
Is it still something that needs to be done even with the auto balance and auto everything ?

In that case Gordon, do you get more accurate colors because the white balance is adjusted on a white card, doing the settings correctly regarding the ambiant light. I am understanding correctly why to do that ?

From my recent experience, you get much better colours doing white
balance from a neutral hue card, (white, grey etc) under the light
source that you are shooting. I believe in most cases the 'auto'
white balance setting is just picking out of the various pre-set
white balance 'temperatures' that are programmed into your camera
(E.g., sunlight, cloudy day, various artificial sources). Could be
wrong though, it might be trying to evaulate it on the fly (anyone
know ?) Either way, you get better, most accurate results using a
reference card and setting it.

Certainly I get much more realistic colours when I do custom settings. I'll put up several versions of this shot to show the difference this weekend if you like.





* This message has been edited by the author on 11/1/2002 12:15:51 PM.
 11/01/2002 12:13:44 PM · #21
Oh yes that would be great. And is it best to do the white balance with a white card or a grey card ? Does it depend on what you are taking a picture of ?
 11/01/2002 03:10:45 PM · #22
Originally posted by lionelm:
Oh yes that would be great. And is it best to do the white balance with a white card or a grey card ? Does it depend on what you are taking a picture of ?


White card or photographic quality grey card will all be fine.
White balance is measuring the comparative amounts of different colours
reflecting from the subject. So as long as the card has equal amounts
of red, green and blue (e.g, a grey card or a white card) then it will
give you the same white balance settings.
 11/01/2002 03:24:37 PM · #23
ok thanks .. I'll read about it then ... I need to learn a little more ...
thanks gordon !
Lionel
 11/02/2002 03:24:34 PM · #24
Very good tutorial. Thanks for posting it.
 11/12/2002 11:53:43 PM · #25
i'm surprised to see that depth of field and depth of focus are confused in this discussion. depth of field literally is how far from the nearest object is the furthest object. a short depth of field is from the lens to a wall five feet away, for example. a long depth of field is from the lens to a mountain some miles away.

depth of *focus* is what is nicely discussed in the article... depth of focus could be termed 'depth of acceptable focus', meaning a near object is in just as clear of focus as a far object. there are three ways to get additional depth of focus:

1) stop down the lens to a smaller f/ stop
2) adjust the focus ring to the hyperfocal setting, based on your distance from the nearest object
3) adjust (tilt) the lens relative to the film plane

more detail about these can be found in most photo books.
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