Using swing for DOF?

[mealers]

Please forgive me if this is a real basic question but its been on my mind for a while and I'd just like to get it straight.
I've had my Shen Hao 4x5 for a couple months now and I'm pretty happy with using tilt and rise and fall on both standards, the one thing I haven't used much is swing but I'd like to experiment.

Say I wanted to take photo of someone keeping the depth of field very small, whats the best way of doing this using swing?

I've been playing around with swing just looking through the GG and the easiest way of getting that small DOF is to use maximum aperture. I have read that LF lenses dont like being used wide open as they lose alot of quality so is there an actual technique used for keeping the object sharp and in focus when shooting wide open and using swing?

Many thanks
Mike

[Daniel_Buck]

I've actually found that most of my large format lenses are pretty darn sharp when shot wide open, a bit softer than f22 or so, but not a whole lot. But not much of the scene will actually be IN focus.

Here is one I did a few weekends ago, having fun burning my last sheet of the day. I used a good amount of front tilt, and then some swing to let the focus follow the fence. The in-focus part of the fence (it's much thinner than what you see on a small web image) is actually fairly sharp, but falls off quickly.

http://www.buckshotsblog.com/wp-content/uploads/2008/09/rileys_09.jpg

[Dave Wooten]

Dan that is an excellent demo....

[ic-racer]

You are right in that swing and tilt will reduce the DOF, compared to having the front and rear standards parallel. Swing and tilt are the same thing, just 90 degrees apart.

To quote from Harold M. Merklinger (Focusing the View Camera):



On the other hand, if limited depth of field is the goal, try for a camera
angle that requires lots of lens tilt.

[Alan Davenport]

Of course, swings and tilts don't really change the DOF. They just change where it is in the subject space...

[Anupam]

Swing is tilt on its side. It won't change dof, but will alter the plane of focus.

Usually to achieve maximum sharpness we choose a plane that will cover most of the subject. To do the opposite, choose a plane that is at a maximum angle (right angle if possible) to the plane that your subject is in. That way, only the line of intersection between the focus plane and the subject plane will appear to be in focus. For example in photographing a face, if instead of the traditional parallel plane of focus you use tilt to have the plane go from near to far, it's possible to have just the two eyes in focus and nothing else. Swing will get you just the nose etc...

[mealers]

Dan - Lovely example!

If anyone has any more it would be good to see them :)

So shooting wide open is the way to go then? I did think that maybe I should stop down to around f/11 and use more swing but I guess I'd run into coverage problems?
I'm looking forward to the weekend so I can have another play already!


On a side note....I made my first ever 16x20 enlargement from 4x5 a couple days ago. WOW is all I can say!!!
After all the stupid mistakes and lots of head scratching while learning, LF for me has been the most enjoyable format I've ever tried!

Thanks for the everyone for the replies and tips.

[JPlomley]

After all the stupid mistakes and lots of head scratching while learning, LF for me has been the most enjoyable format I've ever tried!

Ain't that the truth. I just got a high res drum scan back from West Coast Imaging and ripped a ~ 30x40 in print on Hahnemuhle Fine Art Pearl. Unbeleivable. Just when I was thinking of adding a DSLR kit to the bag, I think I am going to pass and add a 180 mm Rodenstock macro lens instead. No question, LF is a lot of work, but oh the reward is so tremendous when it all works out.

[Leonard Evens]

Let me give you a short primer on depth of field. There is only one plane that is exactly in focus. But points that are not too far from that exact plane may still be in good enough focus that an observer looking at your final print can't tell the difference. The region of space encompassing all such points is called the depth of field.

If you swing, the shape of that region is constrained between two planes, one on either side of the exact plane. All three of these planes meet in a line called the hinge line. If you swing to the right, that line is to the right---looking from the back of the camera towards the scene---and if you swing to the left, it is to the left. Its position is determined by where the exact subject plane needs to go, i.e., bu the scene and the relation of the lens to the scen. The swing angle is determined by the distance of the hinge line and the focal length so it is not something you normally have to option to adjust at will.

Since the region is a wedge, its width, i.e., the horizontal depth of field at any distance is quite short near the lens and widens as you move away from the lens. At the hyperfocal distance its width will be approximately twice the distance from the lens to the hinge line. The width at any distance will also depend on the aperture. As you would expect, it is smaller for larger apertures (smaller f-numbers) and larger for smaller apertures. However, the actual width measured on the ground glass or in a print remains the same for all subject distances.

So let's consider your specific example of a fence trailing into the distance. Suppose you used a 150 mm lens and the plane of the fence passed 1.5 meters to the left of the lens. Then the swing angle would have to be be about 5.7 degrees. If you followed the fence in a print, and measured the distance in focus, it would remain the same as you moved from foreground to background. For example, if , in this example, you swung by about 5.7 degrees and stopped down to f/22, the width on a 4 x5 contact print would be about 22 mm, and about 44 mm in an 8 x 10 enlargement. . At f/11 it would be about half that. But your visual system makes certain adjustments when looking at a print, comparable to what you would see when looking at the actual scene. Points in the print from the foreground which are 22 mm apart as measured on the print will look much closer together than points in the print from the far background which are also 22 mm apart as measured. The reason is that the visual system normally interprets those background points as being further away and compensates by expanding apparent distances. So what you would see would tend to reflect what your visual system expects and you would see the horizontal depth of field as increasing from foreground to background. If the fence extended into the far background, you might find the fence was not as well isolated as you wanted. Also, if the plane of the fence passes far to one side of the lens, the swing angle would have to be much smaller, and that would increase the width of the window in the print. Thus, if it passes 3 meters to the left instead of 1.5 meters that would double the size of the window to 44 mm. The upshot is that you want the lens to be fairly close to where the plane of the fence goes near the camera, and you want to stop down as little as feasible. If the fence is mostly in the middle and foreground, you ought to be able to isolate it as you want.

In Daniel's example, you can see these principle in action. Everything is in the foreground or middle distance. The window in focus at any distance seems to be about 20 mm. That is wide enough for the background, but there is one section in the foreground where it isn't wide enough and part of the fence goes out of focus. It may also be true that the exact plane is not quite vertical, so the result might have been improved by adding a slight tilt to the swing.