Question about View Camera Tilts

[mark_baylin]

Hi all,

 

Here's a view camera movement question that I've been finding difficult to get clarification on.

 

Since I don't do well with diagrams, here's a quick example scene to illustrate my question. Before me is

a landscape photo I wish to take. It contains many trees that I want to keep from leaning. There is a fair

bit of near to far subject relationships.

 

I set up my view camera (folding wood field) and bring up the back to it's neutral position (it gently

locks into place). I then use the tripods head to adjust the forward and backward pitch of the camera

until the bubble level on the back standard of the camera reads in the middle. I then pop up the front

standard to roughly level. I then use a pocket spirit level on the top of the front standard (the front

standard has none by design) and then use the base tilt (forward and backwards) until the pocket level

resting on the front standard reads in the middle. To the best of my ability, the camera bed is level and

the front and rear standards are also now level, thus parallel to each other.

 

My question is: with the camera set up this way, can a front tilt (through the base or axis) extend the

zone of sharpness without stopping down? I've tried to experiment by actually doing this, but the

results are difficult to observe while stopping down. The first thing that seems to happen while looking

through the camera wide open, is the top or bottom (can't remember which just thinking about it) of

any vertical object in the foreground of the scene goes way out of focus.

 

What I do know is when the back and front standards are parallel to each other and the camera is

pointed down into a scene, a front or rear tilt extends the zone of sharpness. The effects of tilting with

the camera pointing down, into the scene can clearly be seen without stopping down the lens, but I'm

having trouble seeing a similar effect when the camera bed and the front/rear standards are all level in

such a situation.

 

Sorry for the length of this letter... hope the terminology makes sense... Any help here much

appreciated!

 

Thanks

 

Mark

[William Kahn]

It sounds like you have the camera set up properly. This is what I posted on an earlier thread on this subject - maybe it will help:

 

Here's a technique that works well with landscape shots:

Compose the shot, using enough tilt so that there are at least two inches of vertical separation on the ground glass between the near and far focus points.

 

If you have a millimeter rule on your focus rail: Focus on the near focus point, and note the reading on the scale. Focus on the far focus point, and note the difference between the two scale readings. Multiply that figure by 5 for 4X5, by 2.5 for 8X10 This gives you the minimum f-stop needed to keep both near and far points in focus. For example, if the difference in scale readings is 4mm, 4X5=20, meaning the largest lens opening you want is at f22. Then, move the focus point back so that the scale reading is halfway between the far and near focus points.

 

If you don't have the millimeter scale, you'll have to estimate the movement distance on the rail, and focus about halfway between the far and near points with the lens wide open (in other words, so that the far and near points are equally out of focus on the ground glass).

[marionovak]

How you guys ever manage to take a shot? Just focus to 20ft in front of the camera, use F32 or F45, and voila! Everything is sharp. Move to the next subject.

 

If you think I'm kidding check teh image I have uplodaed. Camera is hand made 6x12, lens Super Angulon 72/5.6XL, Fixed focus on 20ft, exposure f32 at 1/15, Film Velvia100

[marionovak]

Here is detail from the same shot

[larry h-l]

If the trees extend from near the top to the bottom of the frame, tilting will not help. In this case, only stopping down will work.

 

Now, if you had a scene where there was a significant amount of sky above the trees, and some distant clouds, then yes, tilting the front down would help. In this scenario, the areas that are out-of-focus, or outside the tilted plane of sharpness are "hidden," below ground in the front, an "invisible" in the air. The out-of-focus areas exist, you just don't see them.

[michael_briggs2]

"My question is: with the camera set up this way, can a front tilt (through the base or axis) extend the zone of sharpness without stopping down?" A front tilt can tilt the plane of best focus, but since most subjects are not exact planes you won't get the entire subject in perfect focus just be altering the plane of best focus, without stopping down. Your goal in using a front tilt is to pick a plane that approximates the subject and tilt the front standard to make the plane of best focus this plane. This method isn't a miracle that allows you to get the subject in focus wide open (unless it happens to be a perfect plane); typically you gain one or two stops.

 

Also understand that, because depth of field is larger at larger distances, the depth of focus about this plane will be wedge shaped. So use this as you pick the plane that you want to tilt the plane of best focus to.

 

If you use the focus spread method to determine how far you have to stop down, your goal in tilting or swinging becomes to reduce the focus spread.

 

An axis tilt will have less effect on the overall focus. A base tilt also moves the lens and will tend to require more of a focus correction.

 

The focus spread method that William describes works very well to determine how far you need to stop down to get the objects that you want to be in focus in focus. However, the near and far points do not have to be vertically separated. That is merging the requirements for setting up a tilt and for using the focus spread method.

 

To setup a tilt, you need two vertically seperated points. Rather than my writing up a proceedure, I suggest following the checklist of Howard Bond: http://www.largeformatphotography.info/articles/bond-checklist.html

 

After having setup the best plane of focus with a tilts and/or swing (or none), you can then use the focus spread method to measure how far you need to stop down. The method is described at http://www.largeformatphotography.info/fstop.html. The points used to measure the focus spread should be the most extreme near and far objects that you want to be in focus; their vertical position doesn't matter.

[capocheny]

Mark,

 

To understand what Michael is saying I'd strongly recommend that you pick up Jim Stone's

book, "A Users Guide To The View Camera."

 

[if you can locate the 2nd edition... the print quality is much, much better because they

used a high-end paper stock. The newest edition is printed on a poor paper stock and

costs almost twice as much! :(]

 

There's a terrific image in the book that shows placement of the plane of focus and how a

"cone" is produced. As you stop down progressively more and more the cone opens up

wider and encompasses a greater amount above and below the plane of focus.

 

Imagine a "V" turned sideways. Now, draw a line from the middle of the v outwards. This

represents the plane of focus. Now, as you stop down more and more, the two sides on

each side of the plane of focus moves further and further away from the plane of focus. In

other words, the depth-of-field is increasing.

 

IMHO, it's one of the best illustrations I've seen that shows how these two elements impact

on one another.

 

Hope this helps. :)

 

Cheers

[troyammons]

To understand movements, you need to read a book or take a class.

 

The proper way to shoot a LF camera is zero and level it first.

 

IMO zeroing the camera is critical, but I prefer to frame the subject and disreguard leveling to perfection most of the time.

 

Although the poster is correct up above about stopping down, stopping down to F45 with a super sharp lens will cost you sharpness. If you use a soft lens or a soft scanner like an epson it does not matter as much. Also there are just times you can not tilt. See below. A 90mm lens is probably great for just stopping down to F22 or F32 for DOF but a longer lens might not cut it.

 

Back to tilt. To understand when to use tilt you have to understand what happens to the plane of focus when you tilt. The reason your tree tops are going OOF is when you are tilting the tops are out of the area of sharp focus and that is a wedge shape.

 

When you tilt the lens forward/down, the plane of sharp focus goes from being vertical and equidistant, (IE for instance maybe 15 feet in front of and 15 feet behind the point of focus) .........

 

to a tilted plane of focus that would ideally go from the ground at the base of the camera out, but wedge shaped and maybe only a few inches of DOF at that nearest point expanding out to an infinite dof somewhere far out perpendicular to that plane.

 

Everything in the wedge will be in focus. If you are in the desert and the ground plane is within the wedge everything would be in focus. If you are on the east coast with the same setup and a tree top 40 feet away is outside of the wedge, even though that may be your focal point prior to tilting it will be OOF, the tree top that is.

 

WO the wedge would be narrower than stopped down, but how much is beyond me. I never have figured that out although I am sure it could be calculated. Not sure if I really even want to know.

 

For landscape I typically tilt WO and then stop down to where that particular lens is sharpest.

 

The methods of actually focusing can be found here and there in a search, like the near far method. Easiest is a Sinar with the degree dials that automatically feed back a degree number for proper tilt.

[bruce_watson1]

<i>can a front tilt (through the base or axis) extend the zone of sharpness without stopping down?</i>

<p>

The short answer is no. The (very) simplistic explanation is that tilt is used to tilt the plane of sharpness. It doesn't expand the plane of sharpness. The only thing that expands the plane of sharpness is f/stop.

<p>

Typically with a scene such as you describe, I would set both standards level and plumb and pick an aperture whos hyperfocal distance is sufficient, focus at this hyperfocal distance, and go.

[mark_baylin]

... very helpful and interesting... thanks to all for your answers!

 

Mark

[pvp]

Mark,

As mentioned earlier, the effects of view camera movements are sometimes difficult to visualize. I found Harold Merklinger's online publications invaluable when I first started in LF, particularly his animations showing the effect of various movements. Somewhere in his articles, he also has a discussion of DOF with the lens tilted.<P>

 

A web page with links to many of Merklinger's articles, and the animations, is available at <A HREF="http://www.trenholm.org/hmmerk/HMArtls.html">http://www.trenholm.org/hmmerk/HMArtls.html</A>.

[ndelamerced]

Mark

 

If you want to your trees straight, keep your rear std. level and use the front std to adjust the

plane of focus. The reason why vertical objects become blurry when you use tilts is that the

plane of focus change from vertical to diagonal or from a wall to a ramp. If you want the trees

to be in sharp focus from ground to the tops, either use a shorter lens, or smaller

opening,or a combination of front tilt and smaller opening.

Hope I answered your problem.

Narciso

[michael_alpert1]

Mark,

 

You are leveling the camera correctly; however, to make rotating the camera easier, I would make sure that the tripod head and the base of the camera are level first. Then I would mark the camera's hardware to indicate where they they should be locked in order to have the standards perpendicular to the base and thus level. These locking points will be the same every time you set up.

 

You are not thinking about front tilt correctly. If there are any trees or buildings that are closer than infinity, you cannot use front tilt (or, at best, you will not gain anything). By using front tilt, the upper part of your image will be forced out of focus. Front tilt is useful when you want to photograph across an empty space on a windy day, a situation like a treeless field, for instance, or the sea. In that situaiton, you use tilt to avoid stopping down very much, thus gaining a higher shutter speed. The best way to learn the benefits and limitations of front tilt is through practice. A situation that has "a fair bit of near to far subject relationships" requires stopping down without tilt. Again, on a windy day, given the limitations of film and focal-length, the photograph you want may not be possible. Most people start by tilting the lens too much. Used correctly, the near and far elements of the scene should be in focus without stopping down. Front tilt is, at times, essential; and with practice it is a very easy adjustment.

[henry_friedman1]

You can buy books, take classes, bring a ruler or just sing this little poem to yourself while watching the effects on your groundglass:

 

"Focus for far,

Tilt for near,

Focus and tilt

'til all is clear."

 

As correctly stated earlier, tilt is ineffective if there are significant vertical elements in the scene. And, only very small amounts of tilt are needed.