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laroygreen
3-Mar-2011, 16:04
Good day all,

Been reading up on LF techniques, and I have a question about camera movements as it relates to a specific example.

If you were taking an environmental portrait of someone on a stage, and you wanted the entire scene to be within the DOF, could you achieve that without going to say f64 and without distorting the frame and the main subject (a person)?

Put another way, can you use camera movements when doing an environmental portrait to carry DOF throughout the entire scene, without distorting the main subject (a person)?

Not sure if I'm being clear or not, but I'd really like to know if that is possible and if it is, how its done.

Vaughn
3-Mar-2011, 16:14
Shoot with a very wide angle from far back and then crop.

Brian C. Miller
3-Mar-2011, 16:15
This really isn't about using movements, it's about DOF. Movements change the plane of focus and perspective, but they don't actually change DOF.

For the whole stage to be in the frame, the camera would need to be away from the stage. This would be true even if you were using a wide-angle lens. For the stage to be in focus, front to rear, the only control available is f/stop. Tilting the front lens a little bit would keep the stage and performers in focus for a larger apeture, but the top of the stage would be out of focus.

Bob Salomon
3-Mar-2011, 16:15
Using tilts and swings controls the zone of sharp focus. Using the aperture controls the depth of field.

Think of it like this:

If you are in a theater and put the camera and tripod on the stage and focus wide open you can select any one row of seats and if you focus on a seat in that row the entire row will be in focus but the rows in front and behind that row will be progressively less sharp.

Now if you focus on that same seat and til the lens foward you can get every seat in front and behind that seat equally sharp, wide open. But the seats to either side will no longer be in focus. Stop the lens down and the seat to the side will start to come into the depth of field so the rquired width and depth of seats appear sharp.

Stopping down to f64 on 4x5 will put you into diffraction and that will degrade sharpness, especially in the center of the image as compared to the outside so ideally you do not want to stop down past the optimal aperture of your lens.
There are simple pocket calculators, like the Rodenstock, which computes Scheimpflug (tilt/swing) for any format from 35mm to 8x10 on one side of the calculator and depth of field for most common image ratios for 35mm to 8x10 on the other side. You might find one of these helpful.

laroygreen
3-Mar-2011, 17:09
Ok, so, how can landscape photographers, from what I read, maintain sharpness from the foreground to say distant mountains in the background or how an architectural photographer can shoot a large interior and maintain sharp focus throughout the interior? Certainly that can't be f-stop alone? Or am I interpreting it wrong?

Brian C. Miller
3-Mar-2011, 17:24
This is front tilt, changing the plane of focus.

Imagine you are out in a field, and you want to get the grass in front of you in focus. Tilting the lens forward brings the foreground into focus. Now, imagine that there is a tree in the field. But the tree is near to you, and there is a big limb, say 10 feet up, that is part of your composition. Now if you tilt the front lens forward, the tree limb will be out of focus, but the grass will be in focus. If you tilt the front lens backwards, the limb will be in focus but the grass will be out of focus. At this point your friend is f/stop.

There are a number of really good demonstrations of the Schleimpflug rule, with explanations and photographs. This takes some thought and experimentation to understand, and is best done if you have a camera.

Heroique
3-Mar-2011, 17:37
Been reading up on LF techniques...

Try also the forum article: How to focus the view camera (http://www.largeformatphotography.info/how-to-focus.html).

It might be a long read – but you can pick and choose the best parts.

For example, see the section titled “Estimate the best plane of focus.”

Here’s a juicy excerpt from that section:


“The difficulty comes when your subject is somewhat three-dimensional, and several planes seem to make sense.”

It continues w/ excellent ideas that would apply to your theater.

;)

laroygreen
3-Mar-2011, 17:40
I did go to the library today and spent 2 hours, but what I did find, really skimmed the topic and didn't explain it in a way I understood. But, I'll try again to see if there is anything else on-line I could read that may help.

Edit
Thanks for the link!

Bob Salomon
3-Mar-2011, 18:05
You also need to focus on the correct spot so your DOF will go from the nearest desired point to the furthest.

That means that if you focus on the mountain the DOF will run from some point in front to beyond infinity. So you want to focus on a point 1/3rd into the scene so you maximize the DOF by making it run from the near point to the far point.

For most applications the DOF runs 1/3rd towards the camera and 2/3rd away from the point focused on.

engl
3-Mar-2011, 18:29
Ok, so, how can landscape photographers, from what I read, maintain sharpness from the foreground to say distant mountains in the background or how an architectural photographer can shoot a large interior and maintain sharp focus throughout the interior? Certainly that can't be f-stop alone? Or am I interpreting it wrong?

The landscape photographer can really only do this if the scene lends itself to using front tilt, which is far from always the case. The same goes for an architectural or interior photographer, in a lot of situations tilt/swing won't help.

For some compositions you will find yourself forced to stop down very far, at which point any large format resolution advantage is lost and the exposure time is very long. For those situations, using a smaller format would probably be better. Doing that is essentially the same as the first suggestion, using a wider lens and crop.

For some subjects focus stacking can be a way to work around DOF problems, but it is mostly used with digital, and not suited to shooting anything that moves.

Jack Dahlgren
3-Mar-2011, 19:55
I did go to the library today and spent 2 hours, but what I did find, really skimmed the topic and didn't explain it in a way I understood. But, I'll try again to see if there is anything else on-line I could read that may help.

Edit
Thanks for the link!

You can just think about it.

First - the film is a plane. If the lens axis is perpendicular to that plane, then there is a corresponding plane on the other side of the lens which the lens will focus onto the film plane. Everything on that plane will be in focus (there is some simplification here as lens can have some distortion - but they generally aim to be planar). Aim your camera at a wall keeping the film plane parallel to the wall and the whole wall will be in focus. Things sticking out of the wall towards you, or objects behind the wall will be out of focus in amounts varying with their distance from the plane of the wall.



Tilting the lens will tilt that plane of focus. So if the wall were instead a brick walkway, the whole plane of the brick walkway could be in focus, but things above the walkway, or below it would be out of focus.

If a person is on a stage, the difficulty is choosing which plane you want to be in best focus. Is it the front of the person (implying a vertical plane) or is it the foreground, the person's head and perhaps the upper scenery behind them (implying a tilted plane)

Stopping the lens down works to diminish the amount of focus lost as objects become further from that plane of focus. Stopping down a lot maximizes the amount that would be in focus, but also causes diffraction which softens the overall image.

Balancing focus plane, depth of field and sharpness can be calculated, but it may be easier to just stick your head under the dark cloth and see how it works on the ground glass.

Leigh
3-Mar-2011, 20:34
Tilts or swings control the plane of focus.

Aperture controls how "thick" that plane is, i.e. how far from the plane objects can be and still be "in focus".

- Leigh

Brian Ellis
3-Mar-2011, 20:40
Tilts or swings control the plane of focus.

Aperture controls how "thick" that plane is, i.e. how far from the plane objects can be and still be "in focus".

- Leigh

Not exactly. Only one plane can be "in focus." Everything in front of and behind that plane is out of focus. Those things may appear "sharp" despite being out of focus depending on a number of variables such as degree of enlargement of the print and viewing distance.

Leigh
3-Mar-2011, 20:49
Everything in front of and behind that plane is out of focus.
Hi Brian,

I intentionally avoided using terms like "in front of" and "behind" because they're not relevant to a tilted plane of focus.

What I said was the aperture controls how "thick" the plane of focus will be, meaning distances measured perpendicular to the plane.

- Leigh

laroygreen
4-Mar-2011, 08:19
Ok, I think I understand now. Basically, I can only decrease my f-stop to get a larger DOF, where as movements will determine the orientation of that DOF.

I guess my problem was that I had made assumptions about movements even before I read anything about it.

Thanks all for the help, and rest assured, I'll be back with more questions soon!

E. von Hoegh
4-Mar-2011, 09:07
Not to mention the difference between "depth of field" and "depth of focus".................

Leigh
4-Mar-2011, 09:10
Not to mention the difference between "depth of field" and "depth of focus".................
Depth of field is on the subject side of the lens.

Depth of focus refers to the image at the film plane.

- Leigh

E. von Hoegh
4-Mar-2011, 12:13
Depth of field is on the subject side of the lens.

Depth of focus refers to the image at the film plane.

- Leigh

Thank you. Too many toss the " DOF" abbreviation about; it isn't always apparent which they mean.

I think the OP was putting a hypothetical case, he's made it apparent that he's just getting off the toe of the learning curve. When I was getting into LF in the mid 1980's I had endless confusion arising from misunderstanding jargon and so on.
Another lesson I needed to learn was that LF isn't always the correct tool. For commercial work the "use the smallest format that will do the job" rule is important.
The smaller the reproduction ratio the less DOF (focus) is available.

Leonard Evens
4-Mar-2011, 16:39
You have to understand the geometry of the depth of field region. If the standards are pa rallel, it is a slab perpendicular to the lens axis which extends infinitely up and down and to either side. Its size depends on the camera position and the f-stop. The further bakc you get, the large it will be.

In your case, you don't want to stop way down to increase the depth from front to back of the DOF region because you would then have to use long exposure times and subject motion might be a problem.

If you tilt the front relative to the back, the geometry changes. The DOF region lies between two half planes which meet somewhere below the lens. The line where they meet is called the hinge line. The vertical extent in focus is narrow close to the lens and expands as you move further from the lens. As you focus, the whole DOF region swings about the hinge line, which depends only on the camera position and the fstop. It is conceivable in some special circumstances, that you could include everything that is needed in focus with an appropriate tilt, but usually that won't be the case. It won't be the case, if there is considerable vertical extent needed in focus which is relatively close to the lens. It may be worth a try, but don't be surprised if it doesn't work.

Bob Kerner
4-Mar-2011, 17:14
Rather than treat it as a hypothetical, can you take your camera and actually do it?
Some of this stuff only begins to make sense by seeing it on the ground glass.

rdenney
4-Mar-2011, 17:26
We can write things like: The focus plane, the lens board plane, and the film plane all intersect, and when they are parallel, they intersect at infinity. But we can't make such words have meaning.

But it's easy to learn by having it demonstrated by one who understands it, or even by seeing pictures in books on the subject. A classic book on the subject is Ansel Adams's The Camera.

The text we are stuck with here just doesn't provide much illumination.

Were it me, I would pick three things in the subject that I wanted sharp even with the lens wide open, visualize how the plane going through those three points intersects the film plane, and then aim the lens board at the line representing that intersection. Then, stop down to achieve the necessary depth of field beyond that. If you have studied geometry, that description might be meaningful, but if you haven't, it will be a struggle. Pictures will help.

Rick "suggesting a local lesson" Denney

Heroique
4-Mar-2011, 20:07
...visualize how the plane going through those three points intersects the film plane, and then aim the lens board... Pictures will help.

This picture helps me visualize the two planes, where they intersect, how to aim, etc.

:rolleyes: