Film DOF vs Digital DOF: I switched to digital 18 months ago after shooting film for 40+ years; it takes some getting used to and I have learned a lot lurking around UHH and other...

jbrown

I switched to digital 18 months ago after shooting film for 40+ years; it takes some getting used to and I have learned a lot lurking around UHH and other sites. My biggest adjustments have been focus and sharpness. Am I correct that digital DOF is shallower than its film equivalent, given identical settings? This seems to be my experience and seems to be reinforced by the exif info I have seen on other posts. Thanks in advance for the help.

Wabbit Loc: Arizona Desert

jbrown wrote:

I switched to digital 18 months ago after shooting film for 40+ years; it takes some getting used to and I have learned a lot lurking around UHH and other sites. My biggest adjustments have been focus and sharpness. Am I correct that digital DOF is shallower than its film equivalent, given identical settings? This seems to be my experience and seems to be reinforced by the exif info I have seen on other posts. Thanks in advance for the help.

Hey Doc ..... welcome to digital ..... what camera are you using ..... and I don't think digital DOF is shallower than film .....

haroldross Loc: Walthill, Nebraska

It really shouldn't make any difference. The Canon EF 50mm f/1.4 lens will have the same DOF on a full frame digital body as it will on a 35mm body.

Putting the lens on a cropped frame body, then the DOF will be different because of the crop factor.

The DOF increases as the fucusing distance increases with any given focal length at any given f/stop. Taking a few steps back will change the DOF.

Nikonian72 Loc: Chico CA

DoF is a function of lens aperture, not related at all to any camera characteristic, such as film or digital sensor.

Danilo Loc: Las Vegas

Well, jbrown, there could be several reasons for arriving at the conclusions you state.
Fact is: DOF is a function of lens aperture, lens angle-of-view, and lens to subject distance, regardless of what is behind the lens (film, sensor, glass plate, et al).
You can increase DOF by increasing lens-to-subject distance, increasing lens angle-of-view, or decreasing the size of lens aperture.
Going from a full-frame sensor to a crop sensor does not increase DOF, it decreases angle-of-view. This would force an increase in lens-to-subject distance to obtain the same image, thus increasing DOF.

jbrown

OK! Thanks to all. I thought I was going nuts, becuase it made no sense to me and I didn't think there should be a difference. But I looked at http://www.dofmaster.com/doftable.html and it seemed the DOFs quoted were a bit shallow. I am shooting with a pentax k20d, for 2 reasons: I couldn't decide between Canon and Nikon, and 2. The I.S. is built into the body. (I rarely use it anyway). I have 3 lenses; a 50mm f1.4, and the kit 18-55 and a f4 50-300 Pentax. I have taken some good shots, shoot mostly in spot metering like I alsways did, but sometimes the DOF and focus don't work out. I am used to shooting at f8 specifically for DOF latitude, and it is not working the same for me as it did with my film cameras (Minolta, Nikon, Mamiya/Sekor). It could be the new spot meters use way smaller spots and much more accurate metering. Thanks

Racmanaz Loc: Sunny Tucson!

Nikonian72 wrote:

DoF is a function of lens aperture, not related at all to any camera characteristic, such as film or digital sensor.

<<<< agree's with Nikonian

CaptainC Loc: Colorado, south of Denver

Nikonian72 wrote:

DoF is a function of lens aperture, not related at all to any camera characteristic, such as film or digital sensor.

Oh yes it is. A crop sensor will require the subject-to-sensor distance to be greater to get the same image size and a concomitant increase in DOF. The DOF on a full-frame sensor will be identical to 35mm film.

DOF is affected by Aperture and the size of the subject on the sensor. If you shoot at - for example, f4 - and use a 50mm, 150mm, 200mm, or whatever, but move to keep the subject the same size on the sensor, DOF will be the same. What does change is perspective.

jbrown

Thanks to all. I shoot a pentax k20d with 18-55mm kit lens, a 50mm f1.4, and a 55-300 Pentax f4 55-300mm. I understnad DOF, aperture and the relationship from my flm days, just having trouble adjusting to digital. I also think my kit lens and the zoom are "soft". I usually use spot metering as I always have done; and try to shoot at f8 to get DOF, but it does not seem as reliable. Need more practice. Thanks to all.

Nikonian72 Loc: Chico CA

CaptainC wrote:

Nikonian72 wrote:

DoF is a function of lens aperture, not related at all to any camera characteristic, such as film or digital sensor.

Oh yes it is. A crop sensor will require the subject-to-sensor distance to be greater to get the same image size and a concomitant increase in DOF. The DOF on a full-frame sensor will be identical to 35mm film.

If you place an FX lens (like a Nikkor 105G) onto a Nikon FX camera, set to a specific aperture (like f/8), you can chose the camera to record image either as an FX-size image or a DX-size image.
DoF will not change! The only change is the recorded width and height of projected image onto sensor.

Final images will differ in field-of-view, but DoF will be identical.

Sensors - Full Frame (FX) vs APS-C (DX) Field-of-View Comparison

FilmFanatic Loc: Waikato, New Zealand

Nikonian72 wrote:

quote=CaptainC quote=Nikonian72 DoF is a functio... (show quote)

You are both correct. The difference is whether the image size is the same or not.

selmslie Loc: Fernandina Beach, FL, USA

Nikonian72 wrote:

DoF is a function of lens aperture, not related at all to any camera characteristic, such as film or digital sensor.

DOF is also based on the size of the circle of confusion (see Indie Film Gear's "Depth of Field Calculator" ).

For a D7000 sensor the circle of confusion is smaller (.02mm) than for a D700 (.03mm). The pattern of the light sensitive cells also has some effect.

Circle of confusion for film also depends on format: 35mm (.022), 6x6cm (.053mm) and 4x5 (.11mm)

There is more information at http://photo.net/learn/optics/dofdigital/ .

The key statement in this link is "If you use the same lens on a small-sensor camera and a full-frame camera, then shoot from different distances so that the view is the same, the small-sensor image will have 1.6x MORE DOF then the film image." Sounds like he was using a Canon.

On the other hand, if you crop the full frame image to a DX size you would get the same depth of field, but why would anyone do that?

Gill747

I shoot a Sony A55 (crop 1,5).
What I do not understand, lets say you are using a zoom lens, Sony DT 3.5-5.6/18-55 mm and camera set to manual mode.
You set your camera's aperture to F 22. Well, the lens' max aperture is 5.6, correct? Is the F 22 calculated by the camera?
I am finding the sharpness is much better if you set the camera to F 5.6 and adjust your speed and or ISO to achieve proper exposure.

Granddad Loc: UK

DOF on a dslr is governed by the size of the sensor in the camera. You can see this on a compact camera, which has a smaller sensor than whats in a dslr, the DOF is greater.

BboH Loc: s of 2/21, Ellicott City, MD

Another issue could be your len's "sweet spot" which may not coincide with the focal point the view finder is showing. Check the focal point in your image, the area just ahead and just behind it to see if either may be sharper than the focal point (had this issue in a thread yesterday or the day before - don't remember the question). Go to Luminous Landscape and read the essay about LensAlign. LensAlign is a produce but the essay defines the problem nicely