tilting the front or tilting the back or both

[tak_l._poon1]

Dear friends,

 

I understand that when the object is an obliquely oriented but flat plane, we can tilt the lens or the film to obtain

sharpness of the whole object.

 

my question is: should we tilt the lens only or the back only or both?

 

thank you very much in advance.

 

Tak

[sheldonnalos]

Tilting the back alters perspective and focus, while tilting the front just controls the plane of focus.

 

Tilting the front moves the image circle (using up coverage), while tilting the back moves the plane of focus within the stationary image circle (doesn't use up coverage).

 

It depends on what you want/need to accomplish in a given shot.

[jim_gardner4]

Tak, I am fairly new to LF but will try to answer your question. If the object is upright (tall building is the usual

example) and you want it to remain that way in the print, the camera back should be parallel to the object. i.e both

upright. Tilting the back one way would make the top of the buiding bigger and vice versa if you tilt the back the

other way. In this case you would use the tilt/swing of the lens to adjust the focus plane. If the perpspective is not so

important, you could use front, back or both. There is plenty of reading on this subject on the web and many books

have been written about it. Google view camera movements and you will find loads of stuff. Also try to imagine the

image coming through the lens and getting bigger as it comes towards the film back. As you move one part of the

back further away, the part of the image that will fall on that part of the film will be getting bigger the more you move

the back away from the lens. Also imagine a plane of focus parallel to the lens and film when everything is in

its "normal" position i.e no movements. When you swing or tilt the lens the focus plane will move in the same

direction but will not be parallel to the lens. That is to say the focus plane will move to a greater degree than that

which you have moved the lens. Others could probably explain this much better than that and as I am fairly new to it

and a little knoledge is a dangerous thing, I suggest you keep reading, get some books and use some film and look

at the results.

[jim_graves1]

I think the simplest way I've heard it said is to first compose the picture using back movements and then adjust the focus plane with front movements.

 

Back movements allow you to control convergence/perspective both vertically (tilt - e.g. tall building vertical lines) and horizontally (swing - e.g. long building shot from corner.) With back shift (vertical and/or horizontal) you can adjust the portion of the whole image you want on the film (useful, for instance to shift the camera's reflection out of a picture without changing perspective.) Once the image is correctly composed move from the back to the front to adjust the plane of focus.

 

With the caution thrown in that most people over-shift/swing/tilt ... so keep them to a minimum.

 

As suggested above, a good guide book and then experimentation helps a lot. Try Steve Simmons book "Using The View Camera" or Leslie Stroebel "View Camera Technique," or Jim Stone's "A User's Guide to the View Camera."

[leicaglow]

Tak, if you're fairly new to LF photography, I would highly recommend you work mainly by leaving the film plane where it is and working with just the lens board adjustments to start. Learn all you can about that, and then work with the back plane. The exception to this is if you have a Sinar (maybe other manufacturer's too) that have calculators to help you optimize your movements for the depth of field.

[bob_salomon]

Back tilts and swings control the plane of focus and will modify the shape of the object.

 

Front tilts and swing control the plane of focus but do not effect the shape of the object.

 

So, if you are shooting a square and use back tilts, and the camera and back are perpendicular to the object the object will

no longer be square when doing a back tilt or swing.

 

If the camera and back are perpendicular to the object and you do a front tilt or swing the object will still be square.

[tak_l._poon1]

thank you all for your kind help and quick answers.

 

indeed I am fairly new to large format. Having done mainly medium format in the past. I had been quite successful with macro of flowers as all I need was stronger flash and longer bellows. The calculations were pretty much the same.

 

however, I tried to take photo of a model locomotive, with the rail at an oblique plane to the camera. Now no matter how small I squint the aperture, I cannot bring the whole locomotive into focus. with a large format, then one must use the tilting function. I have been experimenting with different techniques after doing some reading and reading what has been mentioned above.

 

I have just done a number of photos with front tilting only, back tilting only, and varying degree of combination of both. Of course I am still waiting for the results. It takes some time for the films to get developed.

 

(I am not complaining about the time lag to get LF films back. I am lucky to get LF service at all. All the shop keepers are saying that I am moving backward in history and should instead buy DSLR that they are promoting.)

 

thanks again.

 

Tak

[big toys are better]

View cameras are wonderful tools for correcting perspective issues that a fixed lens camera will necessary be

unable to correct.

 

First things first--

 

IF you insist on the tracks being oblique to the camera, then you need to take advantage of an old standard

technique-- putting the planes of desired focus, the lens plane and the film plane all pointing to a common

point-- the farther away the better. IF you are focusing too close AND the angle is too great, then your depth of

field just can't accomplish your goal.

 

Take three yardsticks (or their equivalent) and place them in alignment with those three planes-- the film back

(back standard), the front (lens) standard, and the train tracks. Adjust these until you get them meeting at a

single point, then focus carefully and maximize your f-stop for maximum depth of field. Take careful note of any

focus shifts in the final image that are caused by stopping down the lens, and correct for this.

 

IF you still don't get the tracks in focus, then two more possibilities:

 

Either make the divergent angles smaller (thereby flatter, and thus their common meeting point is farther away),

or add in a second corrective shift by tilting the front standard forward to place the tracks in that plane of

focus as well.

Doing so makes the plane of the "land" that the tracks are on a little bit more within the plane of the lens'

focus plane. Of course, this may then place something else outside the final plane of focus, so be careful.

 

IF you read the books suggested above, this will be easier to understand....

[laurentbaig]

Ok, you've got multiple similar answers for the technical aspect. The next thing is to try front tilt only and rear tilt only and both and see which you like. I'd also recommend Steve Simmons' book, lots of good examples in there.

[tak_l._poon1]

Dear Friends,

 

got my films back. none of them perfect. guess I still need to pay my learning fees. while tilting the front only, the back of the locomotive is too dark. when only the rear was tilted, the whole locomotive is too dark, but the front of the train is even darker still. tilting both planes theoretically should produce an even illumination but the result was under-exposure but both the front and the rear end of the train were darker. This illumination problem was not mentioned in the books that I have.

 

will continue experimenting tonight.

 

cheers,

 

Tak

[leonard_evens]

If you are doing close-up photography, you also have to compensate for bellows extension. That means you have

to increase exposure to compensate for the fact that the film is further from the lens than would be true for a

distant subject. There are a couple of ways to do this. The simplest is to put a disk of know diameter at the

point of focus and then measure its diameter on the ground glass. The ratio of that measurment to the actual

diameter is called the magnification. You then add 1 to it, square the result and multiply the time of exposure

by that number. For the scene you describe, I would get is would be about 0.5 or 1/2. Suppose that it the case,

then 1 + 0.5 = 1.5 and its square is 2.25. If you exposure meter tells you to expose for 1 sec, you would

expose instead at about 2 1/4 seconds

 

But it is probably easier to adjust the f-stop instead by opening up the appropriate amount. Here is a table to

tell you haw much to open up in fractions of an f-stop

 

magnification / #-stops

 

0.1 / 0.28

 

0.2 / 0.53

 

0.3 / 0.76

 

0.4 / 0.97

 

0.5 / 1.17

 

0.6 / 1.36

 

0.7 / 1.53

 

0.8 / 1.70

 

0.9 / 1.85

 

1.0 / 2.0

 

In using this atable it is fine to round off to the nearest third or half stop.

 

In the example where the magnification was 0.5, if you opened up by about 1 and 1/3 stops you would probably be

okay.

[leonard_evens]

I should have added that you can download something called Quickdisk, which does it all automatically for you. Try a google search if someone else doesn't provide a link.

[big toys are better]

As noted above, you do need to compensate for lens extension with any significant degree of closeup. You must also consider the effect of camera movements for the same reason since the film will be farther away from the lens on one side but just the opposite on the other. Adjusting lighting may be the most effective way to correct for differences in light at the film plane due to camera movements but no so for bellows extension where a relatively simple correction in time or aperture is all that is needed. Careful filtering with differential neutral density filters may work as well for the exposure effects of camera movements. If the final setup is complex, both lighting and filtering adjustments may be necessary (and perhaps even darkroom or digital magic still needed), but that is the wonderful thing about product photography under controlled lighting.

[tak_l._poon1]

Dear Leonard, thank your for your suggestion. I have already gone through that. without tilting, all exposures for my macros are correct. for my LF, I do not round off. I found that even 1/10 step change of exposure causes a discernable difference.

 

Dear Hofland, thank you for your suggestion. What I figured out is that first, if tilting the front element alone, the image of the far end of the object falls at the edge of the coverage of the lens and becomes darker. if I tilt the rear element alone, the image of the front end has a larger magnification and thus becomes darker. The best perspective that I would like to have is a combination of both front and rear tilt. This makes the illumination problem very complicated. The change over the entire field is not linear, therefore a central gray filter or gradation filter does not work for me. I am now trying to illuminate the field with 3 variable spot lights. since I do not have a ground glass spot meter, I have to experiment with different settings and then record down the best combination, so that I can reproduce the results a second time.

 

Cheers,

 

Tak

[leonard_evens]

Tak,

 

I've done the analysis to see how the normal fall-off is affected by a tilt. Unless the tilt angle is pretty

large, the tilt shouldn't affect things that much. I suspect that the big difference you see is mainly due to

the fact that one part of the scene is close to the lens axis and the other part is far from the lens axis, and

you are seeing mainly fall-ff from center to edges, with a small contribution from the tilt thrown in. If your

lens follows the normal 4th power of the cosine law that could conceivably result in a two to four stop

difference. Even if your lens has only cube of the cosine fall-off, this could amount to a significant

difference.

 

So your best strategy would be to use a center filter to deal with the lens fall off and make the fall-off

symmetric with respect to the center of the picture by placing the latter roughly where the lens axis intersects

the film plane. The simplest way to do

that is to use back tilt. But you can also do it by using front tilt plus rise/fall or shift of one or both the

standards and repositioning the camera relative to the scene.

Of course, there are limits to such movements, so it may not be possible to do it the second way, depending on

the details of the scene

[tak_l._poon1]

Hi, Leonard, I should have give you more details for the analysis. the rail of my locomotive is at an angle of 60 dg with the film plane before any tilting done. this is quite a significant obliquity. I use a macro 180 mm lens. The train was 1/87 scale, about 20 cm long. Tilting the lens element alone needs about 40 dg of tilt, which indeed puts the image at the edge of the lens coverage. I agree with you that to use additional back tilt should make the illumination more even. That need to be done anyway because I like the perspective. I failed to do that because I had run out of flash power and the whole scene was dark. I do not actually have a centre filter. The earliest one would be 4 weeks away, that is if I order it. The 3 spot light illumination that I have tried also failed because at the overlap of the spot lights there was over illumination. Last night I tried flashing 3 times with B shutter under total darkness. Hope that helps.

 

Tak

[tak_l._poon1]

I would like to thank all who had given their kind thoughts and suggestions to me here. The final picture was a success technically. The perspective is good. The whole thing is in focus. Lighting is also good. I have definitely learned a lot in positioning of the lens, film back and lights, and also the special compensation that I need. In the process I also had to throw away my bosscreen and to use a fresnel for better visually assess the lighting condition. The final product is a film and since I do not have a scanner I have to do scanning with a lab. I shall post my picture up here later.

 

Unfortunately there is some dust on the model, randering it useless in magnification. Such dust grains were invisible in my old medium format photos. That is something I need to learn too. As I have already returned my model I cannot repeat the shot of that particular model.

 

But it had been a wonderful learning process.

 

Thank you all again.

 

Tak