How small do your tilt angles get?

[Leonard Evens]

I've been trying to make some estimates, and it would be helpful to know how small the tilt angle can be in practice. Also, under what circumstances would you use very small tilt angles and how do you make sure you have got it right.?

When I use tilt, the angle is usually at least 2 or 3 degrees. For my camera, a tilt angle of less than 1 degree would be almost impossible to set accurately, and it would be difficult to distinguish the result from the standards being parallel. I sometimes try a very small tilt in the hope that I can improve things slightly, but I find it very difficult to tell if I have by looking at the ground glass, even after stopping down. I have to wait and look at the resulting negative, which is of no use in the field.

So any information about what others do would help me make my theoretical calculations, which probably no one else is interested in, but might also help me when taking pictures.

[David A. Goldfarb]

Out of curiosity I just set up my Tech V to see how small a front tilt I can set, and I agree--I wouldn't likely use a tilt smaller than 2 degrees, and if I did, it would be hard to set reliably. I could set a 1 degree tilt on the rear standard, but I tend not to use rear tilts for focus issues, and if I need a slight tilt to square up objects in the frame, I'm more likely to move the whole camera.

[Vaughn]

I have never measured the amount of tilt I use in a photograph -- I just tilt the amount I need -- very little to very much. My cameras (4x5, 5x5 & 8x10) do not have indents nor scales...and seem to be able to smoothly go from negative tilt to positive tilt.

All is done visually on the GG.

vaughn

[Bill_1856]

If you're tilting to coinside the vertical plane of the film back, the earth, and the plane of the diaphragm, it's easily calculated (though I don't know why anyone would want to). For a 6" lens mounted 66" above the ground, the angle is arctan of 6/66 or about 5 degrees. For a 12" lens it's about 10 degrees. Obviously would be less if you raise the camera, or more if you lower it.
(Someone should check my figures since it's been over 55 years since I took trig.)

[ic-racer]

Not sure I get the question. Are you referring to the zero detents interfering with small tilt angles? With the Horseman 6x9cm with the 65mm lens is somewhat difficult to do any tilt because once you get the lensboard frame off the zero-detent, the tilt is too much in many cases. For me, this difficulty only occurs with short lenses and small formats.

With other cameras the tilt angle is whatever is required for the scene.

[Leonard Evens]

Not sure I get the question. Are you referring to the zero detents interfering with small tilt angles? With the Horseman 6x9cm with the 65mm lens is somewhat difficult to do any tilt because once you get the lensboard frame off the zero-detent, the tilt is too much in many cases. For me, this difficulty only occurs with short lenses and small formats.

With other cameras the tilt angle is whatever is required for the scene.

The zero detents are part of the problem, but it is more than that. I could in principle move the standard enough to produce a 1 degree tilt or swing, but I can't position it exactly enough to be sure I'm not off, possibly by as much as 1/2 degree.

Of course it is much easier to set the tilt if the mechanism is geared. Are there view cameras which have geared tilt and swing?

[Donald Miller]

The zero detents are part of the problem, but it is more than that. I could in principle move the standard enough to produce a 1 degree tilt or swing, but I can't position it exactly enough to be sure I'm not off, possibly by as much as 1/2 degree.

Of course it is much easier to set the tilt if the mechanism is geared. Are there view cameras which have geared tilt and swing?

My Wisner has geared rear tilt but no swing. I would think that the Sinar P models have both.

[Leonard Evens]

I have never measured the amount of tilt I use in a photograph -- I just tilt the amount I need -- very little to very much. My cameras (4x5, 5x5 & 8x10) do not have indents nor scales...and seem to be able to smoothly go from negative tilt to positive tilt.

All is done visually on the GG.

vaughn

I only rarely measure set the tilt angle explicitly. I use the near point/far point method. I guess at a tilt, focus on the far point then note whether focusing on the near point increases the distance between the standards or decreases it. In the first case I tilt more, in the second case I tilt less. After a few iterations there is no focus spread between the near and far point on the rail.

Occasionally I use Wheeler's rule, which uses the ratio of the focus spread between near and far point to the vertical distance on the gg between them. In those case, I measure the distance the relevant edge of the standard moves from the vertical and compare that to the distance of that edge to the tilt axis.

[David A. Goldfarb]

The Sinar P does have both geared asymmetric tilt and swing, plus friction controlled base tilts for large tilt movements as you might use to get indirect rise/fall. When I'm not using the Sinar P, I don't usually measure the tilt angle, but I did it using my Technika for this exercise.

To take advantage of the asymmetric tilts and swings on the Sinar, you need to find the tilt angle using the rear standard, and then read the angle on the scale and set the front standard to the corresponding angle, if you want the tilt or swing on the front standard.

[Once]

I've been trying to make some estimates, and it would be helpful to know how small the tilt angle can be in practice. Also, under what circumstances would you use very small tilt angles and how do you make sure you have got it right.?

---
So any information about what others do would help me make my theoretical calculations, which probably no one else is interested in, but might also help me when taking pictures.

Good news for you, Leonard - You can make whatever small angle you like even on your non geared standards! How? If you use shims of a given thickness at a given distance from the pivotal point of your standard you can easily set whatever small fraction of a degree you need. Just put the shim between the standard's frame and a horizontal reference point chosen on your camera. You can even use the same shim just at a different distance from the pivotal point to get the desired degree fraction. I'm sure you know the math to take care of the rest...

[Alan Davenport]

All is done visually on the GG.

What he said.

I can think of no persuasive argument for abusing myself in an attempt to set a tilt to a particular angle, when inspection of the image on the groundglass produces equal, if not better, results.

That said, with wide angle lenses, tilts get small indeed.

[Nathan Potter]

I set the swing and tilt on my Technikardans only by visual inspection of the GG. But I then record all the swing and tilt angles on the sleeves of the Quick / Ready loads. I just scanned thru about 100 sleeves and found, as David above, nothing less than 2 degrees.

Nathan Potter, Austin TX.

[Dave Jeffery]

To focus using tilt near the zero detent I just tilt away from the zero detent to go out of focus slightly, tighten the tilt knob enough to give the tilt movement resistance, and then squeeze the lensboard frame and front upright slowly until the perfect focus is set. The resistance in the tilt movement stops the frame from popping into the zero detent.
This may not be specifically what you are looking for but hopefully someone may find it helpful.

Have Fun

[ic-racer]

To focus using tilt near the zero detent I just tilt away from the zero detent to go out of focus slightly, tighten the tilt knob enough to give the tilt movement resistance, and then squeeze the lensboard frame and front upright slowly until the perfect focus is set. The resistance in the tilt movement stops the frame from popping into the zero detent.
This may not be specifically what you are looking for but hopefully someone may find it helpful.

Have Fun

I'll have to try that.

[Leonard Evens]

What he said.

I can think of no persuasive argument for abusing myself in an attempt to set a tilt to a particular angle, when inspection of the image on the groundglass produces equal, if not better, results.

That said, with wide angle lenses, tilts get small indeed.

I also set the tilt angle based on what I see on the ground glass, and I don't worry about what it is. I use the near point/far point method, but all such methods are fundamentally limited by depth of focus. My estimate is that the error could be as much as +- 1/4 degree Thus, if I set the tilt twice in a row, the two angles I ended up with could differ by as much as 1/2 degree. For larger tilts that presumably won't make much difference, because the relative error would not be too large. But for a very small tilt, it would be a large relative error. Still, it may be the case that it is not simply the relative error that is important. That is what I'm trying to understand.

Also, a very small tilt would be difficult to distinguish, on the basis of what you see on the ground glass, from no tilt at all. In the rare circumstances in which I've used very small tilts, I didn't rely on what I saw on the gg because that wouldn't have done any good. * I just nudged the standard slightly in the hopes of improving the situation. So perhaps I should rephrase the question as follows. Do you ever find a need to tilt so slightly that you can't see the difference on the ground glass? I would also like to know how much one would tilt in such cases for the purpose of analysis, not because I would try to measure such angles in practice.

*This is not exactly true. In the process of doing my error analysis, I have figured out one way to detect a very slight tilt from the gg. But it is complicated enough that even I would be unlikely to do it routinely, and it is not necessarily related to the actual scene being photographed.

[aduncanson]

There have certainly been times when the subject geometry suggested to me that a tilt would help, so I carefully determined the tilt by viewing the ground glass, and yet when I was done I could not distinguish the tilt from zero by looking at the camera's scales. Have I used tilt in those instances? I am not sure. It seems sort of like a question for a philosopher.

[Once]

I---
So perhaps I should rephrase the question as follows. Do you ever find a need to tilt so slightly that you can't see the difference on the ground glass? I would also like to know how much one would tilt in such cases for the purpose of analysis, not because I would try to measure such angles in practice.

---.

Not before reading this post but now I think it would please you somehow... In such a case I would like to tilt to a 23rd of a degree - for the purpose of analysis, of course, not to see anything on the ground glass or to measure the angle in practice, goodness forbid.

[Michael Chmilar]

Sometimes, when the zero-detent is causing a problem, I will tilt the other standard a little, which allows the standard I am adjusting to move away from the detent range. Crude, but effective. (This is when setting focus by eye on the GG.)

[Alan Davenport]

...rephrase the question as follows. Do you ever find a need to tilt so slightly that you can't see the difference on the ground glass?

The large format groundglass is the original WYSIWYG interface. In an accurate camera, what you see on the groundglass is exactly what you'll get on the film. Therefore, if you can't see the difference on the groundglass, you'll not see it on the film either. Thus, if you can't see the effect of a tilt on the glass, it is impossible to "need" that tilt. So my answer to the rephrased question is, "No."

[David A. Goldfarb]

I don't tilt if I can't see the effect on the groundglass, but I think that it is possible to have a tilt that will show up on an enlargement but might be hard to read on the glass.

[Eugene van der Merwe]

Like most i also use the groundglass as a guide. For some reason i find the difference (in sharpness, ignoring perspective changes) easier to spot when applying a rear tilt than when doing a lens tilt, so in those cases tilts can be as little as 2 degrees. For lenses shorter than 90mm on 4 x 5, i'll often rather use rear tilts since, particularly when shift/rise is also used cutting the corners of the image circle becomes more likely.

[Leonard Evens]

First, let me report the results of some experiments. I put my camera at various heights over some horizontal plane to see if I could detect any focus shift between a near point and a far point. Using a 150 mm lens, at height about 15 meters, the associated tilt would be about 1/2 degree. I couldn't detect any focus shift. At height about 5 meters, where the associated tilt would be slightly under 2 degrees, I could detect a shift of about 1 mm. Given that I just used my 2 X glasses, where my normal focusing error (due to depth of focus) could be 0.5 mm or larger, that was consistent with the expected tilt angle. I could have got closer by using a more powerful loupe.

Those experiments, together with my past experince and what several of you reported, suggest that in practice, tilts less than 2 degrees are rare, and tilts smaller than 1 degree are not detectable on the gg.

A couple of other points.

I've already mentioned rare cases in which I would use a tilt despite not being able to set it based on what I see on the gg. I gather from the responses that most people never do that, but some occasionally do so.

Finally, let me remark that while what you see on the gg is a good guide, it is not that simple. What you see depends on the power of your loupe, the quality of the focusing screen, how good your vision is, and other factors. I am not usually surprised when looking at the developed negative or a print, but I usually stop down a bit extra, when I can, in order to account for inevitable errors in focusing, etc. But sometimes I find that despite my best efforts the result is softer in some areas than I would like. I've seen the same thing in prints on exhibition. I really doubt that anyone always gets exactly what he sees on the gg in the final print.

One point I keep making is the following. If you have to stop down beyond f/22 to get the depth of field you want, it will often be difficult if not impossible to do that by just looking at the gg at the taking aperture. In most cases the image will be too dim. You can improve that by using a bright focusing screen, but there is a limit to how far that will go. I have a Maxwell screen which is exceptionally bright, and I can't see much of anything past f/16. A younger person with better dark vision will probably do somewhat better, but when I polled this forum a few years ago on this subject, I don't think anyone claimed to be able to see well enough beyond f/22 to judge DOF.

One way to deal with the dimness is to use a higher power loupe. I'm not sure why that works but it appears to do so. The trouble is that a loupe in effect decreases your CoC. One can make the argument that a 2 X loupe shows approximately what you would see in a 2 X enlargement at normal viewing distance (or a larger print from proportionately further away.) If you use a 4 X loupe, you divide the viewing CoC in half, which means you in effect double the f-number you need to have everything you want in focus. Of course, if you stop donw something like two stops more than absolutely necessary, then you will get everythi8ng you want in focus. But you may also have to use too long an exposure problem. I am particularly sensitive to that because even a slight wind can blur foliage if the exposure time is too long, and that is often a problem for the kinds of pictures I take. I frequently find myself debating whether I should stop down just a bit more to get the DOF I want to to worry more about leaves blowing in the wind.

So what I do is the following. I focus using the near point far point method by seeing where on the rail those points are in focus and focusing halfway in between. Of course, I also look at the gg and make adjustments based on what I see. I set the tilt by a method based on what I see on the ground glass, though occasionally I use Wheeler's Rule, which requires some measurments and calculation. I calculate the needed f-stop based on the focus spread. (My rule of thumb is multiply the focus spread by ten and divide the result by two.) If that tells me to stop down to smaller than f/32, I also sometimes check what Paul Hansma's table, which tries to take diffraction into account, suggests. I then stop down to see if my choices seem consistent with what I see, in so far as I still can see anything. I also have a rule which allows me to estimate what I would see say at f/32 based on what I can see at f/16, and that helps.

This may seem much too complicated, but it doesn't really take much time to do. I spend much more time thinking about the location of the camera and the framing of the scene, which are by far the most important things. I don't carry a calculator with me since I can do all the necessary calculations in my head.