depth of field question - DPChallenge Forums

Sony 24-70mm F4 Vario-Tessar T* FE OSS

05/27/2009 10:53:25 PM · #1

Ok, I was playing around for the still life challenge, and I liked the condensation on the wine bottle. I can't seem to get a picture with enough depth of field when I shoot indoors. I'm using my 100mm macro lens, but using it as a regular lens. I was about 6-8 ft away, and this was shot at f32. The glass was right next to the wine bottle. When shooting indoor table shots, what lens/distance do you use to get a greater depth of field?

Bear_Music

Samsung Galaxy S24 Ultra

05/27/2009 10:57:52 PM · #2

Originally posted by vawendy:

f/32, 100mm lens, focused at 7 feet, should give you a couple FEET of DOF, kiddo. Something's not computing here.

R.

spiritualspatula

Panasonic LUMIX DMC-LX100

Nikon AF-S NIKKOR 24-70mm f/2.8G ED

05/27/2009 10:59:03 PM · #3

more distance= more DoF, though I can't imagine that F32 wouldn't have been more than overkill for your example....

ETA: too late... Bear beat me to it.

Message edited by author 2009-05-27 22:59:24.

BeeCee

Nikon D40

Nikon AF-S DX Zoom-Nikkor 18-55mm f/3.5-5.6 ED

05/27/2009 11:03:23 PM · #4

You sure that wasn't 3.2?

Bear_Music

Samsung Galaxy S24 Ultra

Sony 24-70mm F4 Vario-Tessar T* FE OSS

05/27/2009 11:03:47 PM · #5

Here's a link to Wolfram Alpha's DOF calculator, btw:

DOF Calculator

R.

dswann

Nikon D7000

Nikon AF-S DX Zoom-Nikkor 18-70mm f/3.5-4.5G IF-ED

05/27/2009 11:09:51 PM · #6

You might try the same shot at f/16 or f/18. Even though a 100mm macro lens will stop down to f/32, the lens will lose sharpness at that setting due to technical reasons that I can't quote at the moment. Most technical articles I've seen on the subject recommend not going smaller than f/22.

05/27/2009 11:11:34 PM · #7

A quick calculation using 100mm, 10 foot subject distance and f/16 gives 1.1 feet (13.2 inches) of DoF. I'm using 0.012mm as the circle of confusion, and this is approximately correct for the 40D.
You should not have to stop down further than f/16, and in fact doing so will give softer results because of diffraction. Make sure your focus distance is correct. Try setting focus manually, and tweaking slightly, taking test shots at each setting.

MelonMusketeer

Nikon D7000

Nikon MF 50mm f/1.4

05/27/2009 11:13:14 PM · #8

Maybe camera shake had more to do with the softness than the aperture setting. With a 100mm lens, it's pretty easy to have vibration, even with a tripod in some situations.

05/27/2009 11:15:01 PM · #9

Stretched out my arms in the dining room--camera is set 5 feet away from the table (maybe a little mroe). I grabbed the wrong picture, it was f5.6.

This picture is f32

I focused on the bottle this time--the wine glass stem looks soft to me

I've had this problem before on my table top shots.

the depth of field calculator looks helpful. What is the circle of confusion?

Message edited by author 2009-05-27 23:16:09.

Sony 24-70mm F4 Vario-Tessar T* FE OSS

05/27/2009 11:15:45 PM · #10

Originally posted by MelonMusketeer:

Maybe camera shake had more to do with the softness than the aperture setting. With a 100mm lens, it's pretty easy to have vibration, even with a tripod in some situations.

I don't shoot with mirror lock up--does that make a big difference?

Bear_Music

Samsung Galaxy S24 Ultra

05/27/2009 11:48:49 PM · #11

Originally posted by vawendy:

Originally posted by MelonMusketeer:
Maybe camera shake had more to do with the softness than the aperture setting. With a 100mm lens, it's pretty easy to have vibration, even with a tripod in some situations.

I don't shoot with mirror lock up--does that make a big difference?

Tripod and mirror lockup make a BIG difference yes. Here's a brief statement re: relationship of DOF and Circle of Confusion:

The depth of field is the region where the size of the circle of confusion is less than the resolution of the human eye (or of the display medium). Circles with a diameter less than the circle of confusion will appear to be in focus.

Here's a link to wiki on CoC:

Circle of Confusion

It's a complex topic. In any case, stopping down beyond f/16, say, on a 100mm, is to be avoided. ON my 10mm, f/8 is about as far as I like to go, and no further than f/11... Generally, it looks to me like you're having issues that have little, if anything, to do with DOF and are related to other factors. I'd suggest making a bright, crisp setup for practice purposes, one with a lot of contrast where you can really nail the focus, and try shooting that at different f/stops.

Incidentally, as a rule of thumb, the DOF extends 1/3 in front of the point of focus and 2/3 behind it. So if you have 12 inches of DOF when focused on your wine bottle, say, then 4 inches of it is in front of the wine bottle and 8 inches of it behind the wine bottle. You have to choose where to focus to maximize DOF over the area where you want it. In a studio setup, we'd frame up the image, then use a tape to measure precisely the near and far limits we needed to have on focus, then we'd use a DOF calculator to derive from that the f/stop needed and the precise distance at which to focus. Then we'd use a focusing marker inserted into the scene to attain that focus. This was primarily when photographing architectural models, which we did a lot of, but it's a general rule for all sorts of commercials setups.

R.

spiritualspatula

Panasonic LUMIX DMC-LX100

Nikon AF-S NIKKOR 24-70mm f/2.8G ED

05/28/2009 12:10:36 AM · #12

Here is a good explanation of diffraction and it's effects on photography. Diffraction site.

Lytro Illum Light Field Digital

05/28/2009 07:52:46 AM · #13

Thanks all!
I'll play around with this. It's been a frustration in a couple of different challenges--I'm usually shooting from much farther away or larger things close up. Miniatures, especially were a problem. When everything's so tiny, it's really obvious when it's out of focus!

MelonMusketeer

Nikon D7000

Nikon MF 50mm f/1.4

05/28/2009 09:06:04 AM · #14

When you stop the aperture down, the open shutter time has to be doubled for each stop to get the same exposure value or "EV". For instance, if the correct EV at f5.6 is 1/125 sec, you would be shooting at 1/15 sec at f16 to get the same EV.
For subjects that don't change much while you are shooting, you may also want to use a remote shutter release, or the self timer in the camera to remove the hand shake from the equation. Try looking through the viewfinder with the 100 mm lens, and with the camera turned off, and you can see the motion caused by pressing the shutter button. If you want to see how much vibration and hand shake you are getting, strap a small laser pointer to the side of your lens with rubber bands, and watch the spot on the far wall of the room. I use the self timer set at 2 sec quite often for hand holding shots, and the difference in the sharpness of hand held images is quite noticeable.
ETA, I always thought that "circle of confusion" was a reference to forum threads discussing challenge descriptions.

Message edited by author 2009-05-28 09:09:41.

yakatme

Nikon AF-S Nikkor 17-35mm f/2.8D IF-ED

05/28/2009 09:11:03 AM · #15

Originally posted by Bear_Music:

Here's a link to Wolfram Alpha's DOF calculator, btw:

DOF Calculator

R.

Something seems wrong with that calculator.

I tried to input a typical shot that I've been doing lately in which my goal is to achieve what appears to be 100% depth of field throughout my image.

Here's my input data:

focal length: 13 mm
f-number: 4.5
focused distance: 5 m (I also tried spelling out 'meters')
circle of confusion: .25 mm

Here are the results:

The near and far limits shown are closer to me than the focused distance that I entered.

Am I reading and/or doing this wrong?

I am wondering if I can use my Tokina 12-24 at about 13mm and get 100% dof throughout my image from about 6 feet to infinity without having to use anything other than the largest aperture. I am shooting in dark and stormy conditions from a kayak and need to maintain enough shutter speed to keep the image sharp.

bjoern

Canon EOS-5D Mark III

Canon EF 24-105mm f/4.0L IS

05/28/2009 10:28:36 AM · #16

Originally posted by yakatme:

circle of confusion: .25 mm

That is wrong - it should be 0.025 mm

DrAchoo

Panasonic Lumix DMC-LX5

Canon EF 24-105mm f/4.0L IS

05/28/2009 11:11:23 AM · #17

Did you use a halogen light for the lighting and then color correct? I've seen image degradation from this before as camera sensors don't deal with reds as well as other ranges and the halogens give off a very red light.

yakatme

Lytro Illum Light Field Digital

Nikon AF-S Nikkor 17-35mm f/2.8D IF-ED

05/28/2009 05:38:51 PM · #18

Originally posted by bjoern:

Originally posted by yakatme:

circle of confusion: .25 mm

That is wrong - it should be 0.025 mm

It should be 0.025??? I thought the circle of confusion was a variable that I determined based on what I considered acceptable. Otherwise it wouldn't be changeable. I chose .25 mm because of the greater distance from my subject (the foreground) which means that I wouldn't be able to discern anything 0.025 mm in diameter anyway.

But maybe I'm totally confused about it. I don't understand how the circle of confusion factors into the equation anyway and how it would affect the final determination of dof.

Whatever value is used for the circle of confusion, the dof should at least be before and after the chosen focus distance. It didn't compute that way however.

05/28/2009 06:52:11 PM · #19

Yep, it seems the Wolfram calculator is giving erroneous results, which is odd, because it seems to be fine for longer focal lengths, and seems reasonable for small focal lengths when the focus distance is short. But it should *never* report a negative DoF. Something is amiss. I'll test this a little further when I get home.

05/28/2009 06:57:14 PM · #20

Originally posted by yakatme:

But maybe I'm totally confused about it. I don't understand how the circle of confusion factors into the equation anyway and how it would affect the final determination of dof.=

And thus it's name ;-)

Actually, you will hear different opinions about what the Circle of Confusion *should* be set to, and yoiu can make a good, logical case for very different values, especially if you are talking about viewing prints made from the images. For judging whether you will make an image *on the sensor* that is less blurry than the sensor can detect, set your Circle of Confusion value to twice your camera's pixel pitch. For instance, for the OP's Canon 40D, the pitch is 5.7Âµm, or 0.0057mm, so setting CoC to 0.011mm is optimal under the conditions I cited.

Canon EF 24-105mm f/4.0L IS

05/28/2009 09:53:40 PM · #21

OK, the Wolfram calculator seems to puke whenever the far limit of focus is at infinity. The denominator in the equation goes negative, driving the far limit negative, and invalidating the result. The near limit seems fine and correlates well to DoFMaster, which is the one I've always used.

DrAchoo

Panasonic Lumix DMC-LX5

05/28/2009 10:29:41 PM · #22

Originally posted by kirbic:

Well...DUH!! ;P

yakatme

Lytro Illum Light Field Digital

Nikon AF-S Nikkor 17-35mm f/2.8D IF-ED

05/29/2009 06:28:57 AM · #23

Originally posted by kirbic:

Now that one seems to work, or at least confirm what I've been thinking.

Again, I was trying to confirm that I could use my Tokina 12-24 at 13mm (to avoid vignetting with polarizer) to get 100% dof from the ground (or water) just in front of me to infinity without stopping the lens down. I need to keep a decently fast shutter speed since I'm shooting from a kayak and although I sometimes stick a tripod into the sand/muck, it's a hassle.

This DoFMaster calculates that I can focus on a point 8 feet away and have acceptable dof from 3.5 feet in front of me to infinity without stopping down the aperture.

Thanks

kirbic.

Message edited by author 2009-05-29 06:29:29.