DOF & Focusing

[Pawlowski6132]

So, I have shot primarily portraits with some occasional indoor still lifes to date in my short career as a LF photographer.

This weekend, I dragged the stuff out to experiment with some landscape shooting; in interesting tree line in a snowy field. Of course, the exposure was a complete disaster which I'm not surprised by. However, it seems like the focus was horrible also.

I'm assuming that it has something to do with DOF. It's hard to mess up with indoor portraiture because I can measure everything and calculate DOF. Plus not having to stop down past f11, I'm comfortable with what I see at f5.6. However, stopping down to f22 in the field, I think screwed things up.

Their was about 200 yards of field between me and the tree line. I focused on the trees (at f5.6) and then stopped down to f22. Seems like the entire image was out of focus. At these distances and at these apertures, do I need to be concerned with trying to understand hyper focal distances? Is it normal to "re focus" under actual actual aperture settings?

I don't know how you landscape guys do it; esposure, focus, the elements. God bless you.

Thanx in advance for the tips.

Joe

[ret wisner]

which camera are you using?

[Joanna Carter]

If the trees were sharp on the screen at f/5.6, they should be in the middle of the DOF at f/22. Hyperfocal distance is not something I bother with because, most of the time, I use front tilt to get everything in focus.

If the image was sharp on screen at f/5.6 and the neg was soft, I would suspect that either the screen or the film holder were out of register.

[Pawlowski6132]

which camera are you using?

Calumet 4x5 Rail w/210mm

Thanx for looking.

[Kevin Thomas]

As you have had good results with the camera and lens shooting at wider apertures I would suspect you might have accidentally moved the front or rear standard after focusing.

Another possibility might be camera shake if it was a very long exposure.

[J D Clark]

The dreaded "W" [wind] can cause the shake Kevin mentions even at 1/8 or 1/15 seconds. I got more soft photographs when I changed from Tri-x exposed at 1/15 and 1/30 to TMAX exposed two stops less (same aperture for desired depth of field) when photographing even in slight winds.

Using an umbrella, or your body to "shade" the camera from the breeze can help. I got sharp photographs in a 35 mph wind with the wife holding a golf umbrella (barely) to shield the camera and tripod.

Unless I'm missing something, if you're getting good sharpness inside with the same camera/lens, then I would think the ground glass and holder were in proper registration.

John Clark
www.johndclark.com

[Doremus Scudder]

Joe,

As mentioned above, if you focused on the trees at f5.6 and then stopped down to f22, those trees should be in the middle of the depth of field and should be very sharp. F22 is normally the sharpest aperture on a large-format lens. Something else is your problem.

To digress for a bit, you can, and should, check depth of field at the aperture you plan to use to take the photograph with. LF is very WYSIWYG, and, with a decent loupe, you should be able to tell which portions of your image will be in focus and which not.

If the entire image is out of focus, I (like the posters above) would suspect (in order of frequency in my experience) camera movement, accidental "unfocusing" by moving the camera back or focusing knob inadvertently, buckling of film during a long exposure, improper insertion of film holder, or misalignment of ground glass and film plane (likely not a problem if your studio stuff is coming out well at relatively wide apertures!).

As far as hyperfocal distance goes, this is usually a down-and-dirty focusing technique for action photographers. If you are taking time to crawl under the dark cloth, you don't need to fiddle with hyperfocal scales. One technique, however, that might be of use to you is the "near-far" focusing technique. In a nutshell, you compose your picture, focus on the closest object you want to be in focus, note the position of the camera back (or front, if you use front focusing), then focus on the far and find the difference in distance between the near and far focusing positions of the camera standards. Then you consult your (or someone else's) handy table of optimum f-stops to use (look here http://www.largeformatphotography.info/fstop.html ) and select the stop you need to keep everything sharp.

Hope this helps,

Doremus Scudder

[Wally]

If he has a lens that supports removal of an element to change the focal length (I forget what these are called- I'm getting old!) then focus may shift when he stops down.

With these one should refocus at shooting aperture (difficult, because DOF is greater. Use a good loupe).

[tom north]

I had the same problem some time ago. I don't know what lens you are using, however if it is fairly new (last 20-30 years) there should not be a noticable focus shift. My problem ended up being lack of rigidity of the bed. As I loaded the film holder, a slight movement occured in the back which was just enough to to cause a focus shift. I fixed the problem by getting a Linhof (5 x 7). Although it is an older camera (1960), it locks down rock solid. You may want to check to make sure there is no movement in the front and rear standard and make sure the locks are working.

Best

Tom

[Andrew O'Neill]

If the plane of focus was the tree line, that plane will be the sharpest plane even if you stop down to f/22. Sounds like some other problem. Are you sure you didn't knock the focus out before you made the exposure? I once forgot to lock the back standard on the rail and knocked focus out when I inserted the film holder on my 8x10.

[Bill_1856]

Many lenses have a pronounced shift of their focus plane when the aperture is changed. This is particularly true of older lenses, so with them it is necessary to check the image sharpness at shooting aperture. I have a Staeble Polyplast casket set which shifts 1/8" if stopped down from wide open to f:16.

[Scratched Glass]

Perhaps you breathed on a cold lens element when you stopped down, and didn't notice it. I've done that before.

[Leonard Evens]

It is possible but highly unlikely that the focus shifted when you stopped down. This should not happen with a relatively modern lens unless it is defective in some way. Otherwise, if you focus on a spot at f/5.6, it should remain in focus as you stop down to f/22. I agree with the others that most likely something else happened.

If the point of focus is relatively close to the lens, it should remain pret ty much in the center of the region in focus as you stop down. If the point of focus is further away, the far depth of field will be larger than the near depth of field, but the point of focus should still be well within the total range. If the point of focus is at or beyond the hyperfocal distance for a particular aperture, then every thing from the point of focus to infinity should be in focus at that aperture. The hyperfocal distance for a 210 mm lens at f/22 is about 20 meters (or 66 feet), where this is determined by what you would see with normal vision viewing an 8 x 10 print made from the negative at 10-12 inches.

If you are comparing what is in focus at f/5.6 on the gg to what is in focus at f/22 in the final print, it is possible that there is a significant difference between the position of the gg and the film position with the film loaded. If you are comparing both on the ground glass, it must be something else.