Ever increasing tilt?

[Paul Kierstead]

Still patiently learning to use a view camera.

So, a little bit ago, tired of the weather, I decided to shoot an onion. OK, it is a phase I am going through, a whole produce obsession The relevant pic is:

http://homepage.mac.com/paulkierstead/tmp/onion11.jpg

When I attempted to use tilt using the increasing tilt method (focus point1, tilt for point 2, refocus for point 1, repeat) the tilt just kept increasing and increasing until I reached the limits of front tilt, a considerable amount on the Super Cambo I was using. In each iteration, it only seemed to get worse, i.e. point 1 would be further out of focus then the last iteration. I have used this method successfully on landscape. The two points were the tip of the sprout and the base of the sprout.

It is difficult, with the camera pointed down and the onion at an angle, to determine what exact plane the two points occupied relative to the camera.

Where did I go wrong? Did I attempt to apply tilt when none was required; swing, perhaps? Or did I possibly pick the two points in the wrong order?

I guess I am asking how you diagnose when the iterative tilt adjustment method does not converge.

[lee\c]

I may not be correct but I think I would have not used tilt but since you did not state the f:stop I would probably have used more (smaller hole) f stop. But that is just me. I generally try not to use movements if I don't think I have to. Why not set it up and do it again?

leec

[Leonard Evens]

It isn't possible to be sure without being there and knowing just how the subject was oriented with respect to the camera. Also, it would be nice to know the focal length of the lens.

From the best I can tell, the subject plane---the sprout---makes a very small angle with the film plane. In such a case, either the tilt angle would have to be very small or the bellows extension very short, or some combination of the two. This may not be achievable with your camera.

Here is the rule for finding the tilt angle. Pick two points, a far point and a near point. (In your case they would both be relatively close.) Focus on the far point. Now try a small tilt forward. Refocus if necessary so the far point is in focus and see how the near point point looks. Now focus on the near point and note which direction the standard moves. If you have to increase the lens to film distance to get in in focus, you need to increase the tilt angle. If you have to decrease the lens to film distance to get int in focus, you need to decrease the tilt angle. However, if the tilt angle is small, it will be hard not to overshoot, either when focusing on the near point or when trying to adjust the tilt angle. So in practice it may be impossible to do it.

If you are getting worse rather than better, it is because you are making your corrections in the wrong direction. Even if you start off in the right direction, if you overshoot, it it possible to then keep going in that direction, which of course would then be the wrong direction.

You might be better off just trying to rely on depth of field. You may have done that in the picture you posted, and it doesn't look too bad.

[Ken Lee]

Perhaps it would be easier if you went outdoors and worked with buildings, rather than with irregular objects. Keep in mind that view cameras allow you to adjust the plane of focus, so it will be easiest to learn with objects that are planar. Brick buildings are quite good, quite to tell if you are in and out of focus.

[Cesar Barreto]

Paul,

I'm also an onionphile and suspect that at this magnification, you sure can't count on tilt or swing to solve your focusing problems. You may even select a object plane to be on sharp focus, but DOF will still be awfully short and may get worst as tilting increases. So, I suggest stopping down more and tilting the less. Good luck!

[Paul Kierstead]

Wow, thanks for the help!

Let see, a couple of answers first: It was a 210mm lens (Rodenstock), magnification is somewhere around 1:1, perhaps a little more. I have used tilt a fair bit outdoors with success (well, the tilt worked anyway).

I have no delusions that I am Edward Weston and millions will covet my produce pictures Actually, very few can get past the "but it is just an onion" stage anyway. If it ain't exotic, it ain't good! Oops, slipping into rant mode. Anyway....I have no disagreement that -- in this case -- I would be better off just using DoF, which is what I did anyway since I couldn't get things to improve using tilt. However the shot was an exercise in the pure pleasure of shooting and as a learning experience (re: I am not Mr. Weston), so I wanted to the the technique in a "hard" situation simply as a learning experience even if it wasn't the wisest choice.

Lesson #2 learned: When your tripod is not the steadiest in the world (actually it is the crappy bogen quick release on the 410 that is the problem), doing multiple pops of the flash requires great care to not disturb the camera. The pic has a double image unfortunately. I think holding on the cable release was the error; I should have let it hang or something so I had no possible contact with the camera while shooting.

Anyway, back on topic, I will definitely try this:

"Now focus on the near point and note which direction the standard moves. " ...

the next time I have trouble. I missed this bit in my studies (or it wasn't listed). So many articles tell you how to do things *right* but don't tell you how to detect when you are doing them *wrong* which is just as important IMO.

[D. Poinsett]

Mr. Lee has it.

At close range with a complex shape like an onion, the plane of focus will not intersect the subject in all places. The area most blurry is the bulb. In this orientation, tilt will not help without sacrificing focus of the sprout. With a 210mm lens and its short DOF, this is a difficult shot. You may consider using a shorter focal length lens to increase the DOF. You will still be able to get close.

[Ralph Barker]

On the popular TV program, "Joan of Arcadia", the god character has occasionally reprimanded Joan of having a "failure of imagination". I think that also applies frequently when we try to use tilts to increase DOF - it's not always easy to imagine where the plane of focus is falling within the subject.

In this image, the desired focus plan is really vertical, with the desired DOF extending toward the lens from the sprout of the onion. Thus, I'd agree with the approach of using no tilt, but a smaller f-stop, perhaps with multiple pops of the strobes. The point of focus might be slightly forward of the sprout, so DOF could be used optimally.

Where I could see tilt being used with an onion would be if the onion were sliced. Then, the plane of focus might best be placed along the plane of the cut. The larger issue then would be counteracting the blur of the lens weeping from being in the fumes. ;-)

[Bruce Watson]

I agree with Ken. Easier to learn with big planar objects. But... I didn't do it that way either ;-)

Where did you go wrong? First, you chose a subject that isn't easy. Then you probably used too much tilt in the first iteration. If you go "over the edge" sometimes you just keep going. I did this same "run away tilt" a few times myself years ago. All you can do is rezero everything and start over. It is often surprising just how little tilt you can get away with, so keep the iterations small.

As I see it, you have several choices with this subject.

1) Align the film plane with the plane of the sprouts. No front tilt (that is, front/back parallel). Use DOF to pull in the front of the onion. Most people would do it this way, because the sprouts are the most interesting, and therefore should be in the sharpest focus.

2) Align the film plane with the plane of the sprouts again. Focus on the top of the sprout, and use front tilt to bring in the front of the onion. When you have this, the point where the sprout leaves the onion will be well out of focus. Now, rack the focus so that the focus plane moves about half way to the point where the sprout leaves the onion. Now, use DOF to bring the end points into focus. This method gives you a better chance to bring everything in the scene into focus, at the price of have little in the scene in *sharp* focus.

3) Align the film plane with the plane that intersects the top of the sprouts and the front of the onion. No front tilt. Focus and DOF as #2 above.

There are many more, which I'll leave as an exercise for the reader (you gotta love it). Of all the methods, I recommend #1 because it puts the sprouts in sharp focus, and with the film plane parallel to the plane of the sprouts, you get no distortion of the sprouts. If the front of the onion is a little out of focus, so be it. You could even push it out of focus using a small f-stop. "If you can't hide it - point it out."

[Bruce Watson]

Oh, yes. Nice onion. Nice picture. It's not like you actually need our help - you are doing fine.