stopping down for focus

[Leonard Evens]

Los,

Looking at the complete scene, I see another possibility. It is not possible to be sure without examining the image myself, but it seems that the wicker fence on the right is going out focus fairly quickly, but the picket fence in the background is still in reasonably good focus. If so, it is possible you have a slight swing, i.e, your standards are not paralel. If so, the exact subject plane might be closer to you on the right than on the left, and that might explain what you see. Often, the detent or zero positions for the standards are slightly off because of play.

You can check whether the standards are parallel as follows. Turn the tripod so the lens axis is pointing straight down. When that is the case, a torpedo level placed agains the lens barrel edge will be level in all directions. Then check with a small level right on the gg. It should also be level in all directions. You should be able to make slight adjustments to get them parallel.

You should also do the test I described to see if the gg plane and film plane coincide.

Finally, let me note that the crop you showed represents something like a 5 X magnification. With only a 600 ppi scan, I wouldn't expect the scan to retain enough detail to really analyze what is going on. Also, remember my warning that if you magnify the image enough, you are bound to see some things going wrong. If you are using a 5 X or higher loupe to examine the negative, then you shouldn't really expect what you see in the negative to be perfectly sharp. On the other hand, the near point and far point you used should look equally bad, and they don't appear to in what you posted. So I think there is something going on, either focusing error from shift of ground glass relative to the film or a slight swing or both.

[Los]

leonard,

i did the test you suggested for normal-ness. the front standard was indeed swinging by a little less than five degrees and not sitting in the detent. i was doing the test for dof and thought i had zeroed all the movements. must have bumped it somewhere. swing was locked, but not zeroed. i'd say your eyesight is pretty darn good. once the swing was fixed, the levels were all good.

still, i would think f45.3 would mask such a slight swing. from what you see in the crop, would you expect greater overall sharpness with diffraction? (mind you, the scan if from a flatbed and has not been sharpened). i am using a toyo loupe with a magnification of 3.6x to look at the negatives.

if you don't mind my asking, what has been your personal experience with diffraction at deep stops and modest sized prints, say 20x24 or 16x20?

[Dick Hilker]

Thanks to all for the clarification on GG brighteners. As a newcomer to LF, I assumed they might be something that could be used to brighten an existing GG.

[steve simmons]

5 degrees of swing is actually a lot and that will cause a problem with a straight ahead subject.

Stop worryng about diffraction. It is MUCH less a problem than having only part of the scene in the dof area.

You need to read some of the basic texts on lf. Try User's Guide to the View Camera by Jim Stone, Jack Dykinga's book Large Format Nature Photography, or my book Using he View Camera.

You are confusing your concepts and don't really understand enough about how the camera and lenses function yet. Do some homework, take a class, etc.

steve simmons

[Michael Kadillak]

You can also use a mini mag flashlight with the top taken off exposing the bulb as a focusing tool. Put a couple either on your plane of focus (near and far) or where you want to evaluate focus near and far and it will go from a diffused bulb to a point light source when in focus. Works like a champ.

[Dave Jeffery]

Re: Maxwell screens

I spoke with Bill Maxwell recently and I am wondering if the regular screen is the way to go or to buy the ultra- brilliant model. I am probably going to order the ultra-brilliant unless Ellis or anyone else thinks the regular screen is better. It's for an Ebony 45SU using 110XL, 150 S and 210 lenses for landscape photography.

Thanks as always!

[Leonard Evens]

leonard,

i did the test you suggested for normal-ness. the front standard was indeed swinging by a little less than five degrees and not sitting in the detent. i was doing the test for dof and thought i had zeroed all the movements. must have bumped it somewhere. swing was locked, but not zeroed. i'd say your eyesight is pretty darn good. once the swing was fixed, the levels were all good.

still, i would think f45.3 would mask such a slight swing. from what you see in the crop, would you expect greater overall sharpness with diffraction? (mind you, the scan if from a flatbed and has not been sharpened). i am using a toyo loupe with a magnification of 3.6x to look at the negatives.

if you don't mind my asking, what has been your personal experience with diffraction at deep stops and modest sized prints, say 20x24 or 16x20?

5 degrees is actually a fairly large swing for a 135 mm lens. Also, when you swing, the rules about where to focus are a bit different. First you choose points to the left and to the right which you want to be in adequate focus. The plane of exact focus should go roughly halfway between those points. (See below.) You set the swing so that the plane of exact focus does that. Once you have done that, swing the plane of exact focus to the left and right by moving the stnadard, i.e.. by focusing, until it passes through each of the chosen points to the left and to the right, note the position on the rail for both and determine the focus spread between. Then refocus halfway in between. This should get you back to the plane of exact focus you decided on or fairly close to it. Now use the focus spread to determine the f-stop as usual.

In your particular example, you want the wicker fence on the right to remain in focus, and it isn't, so you probably set the focus in the wrong place for a swung lens. After you had set the swing, you may still have been concentrating on near and far, while you should have been concentrating on left and right. But, I'm not sure this scene is actually amenable to improvement by use of a swing. If you had set the focus position so that the wicker fence were in focus, then you might very well have found the meter and wall to the left going out of focus. My guess is that you would have been better off with no swing.

Let me describe more precisely how you should go about setting the plane of exact focus. Imagine a plane at some distance from the camera perpendicular to its unswung line of sight. Also, imagine two vertical lines, one to the left and the other to the right which define the limts of DOF at that distance. The plane of exact focus should split the region between those lines in two. (However, in some circumstances, you may want to favor one side over the other, and then you would move it closer to the desired side.)

As to my own work, unfortunately, at present, I can't print larger than 13 x 19 inches. I did make one 25 inch wide print by printing three 8 1/2 x 11 sections which I matched at the edges while mounting. Everything in that print looks quite sharp, even close up,. But the subject in this "triptych" is the facade of a building, so all I had to worry about was focusing on one plane. When I look at my smaller prints under magnification, I see what I would expect, given the limitations of my scanner and printing process. I seldom find significant differences in sharpness between foreground and background. But of course, I am not perfect, and sometimes I get the focus wrong. One thing that I've noticed can be misleading, particularly when using a shorter focal length lens. If you look at detail under high magnification in the background, it may appear to be less sharp than similar detail in the foreground. But, of course, the same size object is much smaller in the background than in the foreground, so the foreground may appear sharper for that reason. But I consider this an artifact of looking at the image under too high magnification, and it doesn't bother me. If it does bother you, then you should the focus closer to your far point. When the far point is at infinity, Merklinger recommends setting it there, more or less on grounds of this nature. I don't personally buy his argument, but I do often adjust the focus point to emphasize what I consider important. Photography always involves some compromises, and you have to decide for yourself what you want to emphasize and what is not so important.

[Los]

leonard,

thank you for your insight. i plan to shoot another test and make a print. i'll be sure to share my results with you.

[terrylorch]

Google "hyperfocal distance" for maximum depth of field. I use a light-weight music stand and a tape measure, put the stand at the hyperfocal distance, focus, remove stand, and shoot.