Balancing depth of field

[andre]

Lately I started to get a feeling that many of my portraits lack definition, clarity and resolution (for a lack of a better word).
They just feel like low quality somehow. Although all of my gear is top notch
I started comparing images from different scanners, film stocks, lenses, etc.

(Maybe this attention to sharpness started when I switched from MF to LF recently.)

And I think that my answer lies in DOF. I hardly stop down my lenses. On none of my formats.
I was always looking for the 3D effect and soft backgrounds. And I think that might have just let to a lot soft images that actually looked rather flat then anything else.

I guess there's something like a minimum DOF that I have to keep in mind.

Does that make any sense?

[rbultman]

Sounds like you need to do some experiments to find out what you like. You can achieve greater DOF and still have a soft background by placing your subject farther from the background. Note the distances between the camera, subject, and background as well as the aperture setting and lens used for each shot. Bracket the aperture for a given setup. Try using a shorter lens.

[mdarnton]

Examples, please.

[djdister]

Shallow DOF and/or blurred backgrounds are not tied to an image looking flat. Insufficient contrast between the subject and background can make any shot look bad, whether it is shallow DOF or extreme DOF. Work on subject/background contrast.

[Jmarmck]

Shallow DOF and/or blurred backgrounds are not tied to an image looking flat. Insufficient contrast between the subject and background can make any shot look bad, whether it is shallow DOF or extreme DOF. Work on subject/background contrast.

This is one of my issues as well.

[Jim Jones]

LF equipment testing may identify the problem. For example, a fresnel lens (or lack of one) may shift the ground glass, leading to a focusing error. A dirty lens may cause the image to look flat. Failure to lock down focusing and other movements can cause unsharpness. DOF decreases as format size increases, making focusing more critical.

[Bob Salomon]

A good portrait is sharp from the tip of your nose to the base of the ear. Is that the DOF that you are getting? If not then you have to adjust your focus so that is covered.

When you were shooting small format optimal aperture was much closer to open aperture then with large format. To get the depth of field that you had with the small format you need to be stopped down much more. Additionally, to get the image quality that you obtained on a small format you also need to be stopped down more.

Optimal aperture on most large format lenses is f22. On MF, which is about 25% the size of 45 the optimal aperture is closer to f8.

Try adjusting where you are focused and try other apertures.

[Bob Salomon]

LF equipment testing may identify the problem. For example, a fresnel lens (or lack of one) may shift the ground glass, leading to a focusing error. A dirty lens may cause the image to look flat. Failure to lock down focusing and other movements can cause unsharpness. DOF decreases as format size increases, making focusing more critical.

A properly installed Fresnel has no effect on the image plane. Either the back is adjusted for a Fresnel beneath th gg or it is adjusted for one on top of the gg. The only way the fresnel can effect focus is when someone who did not know how to properly install one put it in the wrong place.
But that person is just as likely to have installed the gg upside down as well.

Another, more common, focus error is by using a loupe that is not properly adjusted to be in focus on the grain of the gg and instead is focused on the top surface of the gg and/or Fresnel screen. That will let you be out of focus by the thickness of the gg and/or the Fresnel.

[goamules]

How is your lighting set up? You said portraits, do you mean a studio setting? Or outdoors less formal? Lighting is everything.

What speed are you shooting at, and what focal length lens? How close (i.e. just head and shoulders, or full body?) It makes a big difference. I shot a portrait I'm pretty happy with the other day "wide open." But it was an F6.8 Dagor, and I was back enough to get some good depth of field. The background is nicely blurred, but not so blurred it becomes an abstract painting. An F3.8 Petzval would have looked much different, and been more difficult to get a shot I like. Try stopping down, and think about is your light even, or contrasty?

[Lenny Eiger]

For me, there is no balance. I like DOF. I shoot everything down to f45, sometimes f64 or f90. I don't like this blurriness... unless there's a good reason for it aesthetically.

Just an alternate opinion....

Lenny