help with focus

[Rick Tardiff]

I need some help here I don't think I am on the right track with my focus. Its very hit or miss. I don't think I am using the movements correctly. I was attempting to have everything sharp in the two attached pics. I closed down to F22 and shot at 1/125 with a 210mm lens. Isn't that enough? Should I be tilting the lens away from the subject to increase DOF. I have two books on large format and try to spend time going through the forum. Any advice in regards to focus would be welcomed.

[memorris]

In many cases you can increase your DOF with movements. The methods I was taught require a way to accurately measure the position of the standard you use to focus. Then focus on the nearest thing you want in sharp focus and take note of where the standard is. Then focus on the farthest point you want in sharp focus and look at that measurement. The difference of the 2, in mm multiplied by 5 will give you your widest aperture to have all of that in focus. Then you move the standard to 1/2 way between the 2 extremes and stop down. This method gives you precise control over DOF.

To use movements it depends whether your front standard has tilt ad swing. Using tilt or swing you change the focal plane in order to reduce the aperture to achieve the desired DOF. If your camera has axial tilt (tilts around a point near the center of the lend board) then you focus on the nearest object then tilt until the farthest object is in focus. Then go back to the near and do it al over again until both are in focus. Then check the measurement as in the near-far method and find the most out of focus object in the glass and focus on it. Taking the difference as before and multiply by 5 you have the minimum aperture setting.

[Rick Tardiff]

In many cases you can increase your DOF with movements. The methods I was taught require a way to accurately measure the position of the standard you use to focus. Then focus on the nearest thing you want in sharp focus and take note of where the standard is. Then focus on the farthest point you want in sharp focus and look at that measurement. The difference of the 2, in mm multiplied by 5 will give you your widest aperture to have all of that in focus. Then you move the standard to 1/2 way between the 2 extremes and stop down. This method gives you precise control over DOF.

To use movements it depends whether your front standard has tilt ad swing. Using tilt or swing you change the focal plane in order to reduce the aperture to achieve the desired DOF. If your camera has axial tilt (tilts around a point near the center of the lend board) then you focus on the nearest object then tilt until the farthest object is in focus. Then go back to the near and do it al over again until both are in focus. Then check the measurement as in the near-far method and find the most out of focus object in the glass and focus on it. Taking the difference as before and multiply by 5 you have the minimum aperture setting.

Thanks for pointing me in the right direction.

[hmf]

If you're trying to use front tilt to increase depth of field along the ground, you would tilt the lens standard forward. However, you would have to take care that you don't lose clarity in the tops of the distant trees, because you are tilting the cone of sharp focus downward.

I was taught a simple poem:

"Focus for far, tilt for near.
Focus and tilt 'til all is clear"

And one rule:
Watch the groundglass, which tells all.

[sun of sand]

focus on trees with knob
tilt for river bank
focus again on trees with knob
focus again on river bank using slight adjustment of tilt

this leaves the center section between the trees and river bank -the river- not well focused
smaller stops f22, f32 and f45 make the river -center section- sharp
check the rock to see which to use
then use a little more lol

[mandoman7]

Its tedious, but a loupe should really be used if you're having focus problems. It takes more time, but it pays off for the beginning worker.

[Rick Tardiff]

Thanks everyone, I wish steve simmons and leslie stroebel were as clear as that in their books.
I will be out as soon as the weather improves here in the northeast putting these suggestions to work. Once again I am thankful for the help I have received form this forum. Rick

[Jacques-Mtl]

Maybe you can have a look at that page http://www.largeformatphotography.info/ there's a link on how to focus the camera.
Jacques

[Rick Tardiff]

Maybe you can have a look at that page http://www.largeformatphotography.info/ there's a link on how to focus the camera.
Jacques

Thanks Jacques I have bookmarked the page.

[jeroldharter]

If you are just starting out:


Put the loupe on the bottom of the ground glass and focus (that is "focus far")
Then put the loupe on the top of the groundglass and tilt the front standard forward [or the rear standard backward] (that is "tilt near").
Then fine focus on the bottom of the groundglass
Then fine tilt the front standard
Then repeat if need be for enough iterations to get things right


The area between the far and near will probably be unsharp. You must stop down sufficiently to bring the middle into focus. F22 on your setup might be insufficient. Don't be afraid to "bracket" with f32, f45, or (if possible) f64 and then evaluate the processed negatives with a loupe to get a feel for the differences and see if diffraction at small apertures results in any visible degradation in sharpness with your setup (I doubt it will).

When you focus far, tilt near, you have to be careful about vertical objects like trees that are in the middle of those two planes. They can be difficult to render sharply and require a small aperture.

Also, sometimes a very small swing can improve the left-right depth of field but you will occasionally screw up everything and have to zero out all the movements and start over. Don't get frustrated and keep repeating until you get the hang of it. I'm no expert but that is how I go about it.

[ImSoNegative]

the i way is focus is this, i will focus on distant, then tilt the back till the near becomes sharp then i will usually adjust the back a bit more by going forward a b it then i stop down usually to at least f22 on a 210mm all should be good and sharp. i very seldom use forward tilt.

[ImSoNegative]

here is an example, this was shot with a 210mm fujinon @f22,

[jeroldharter]

Back tilt will exaggerate the size of foreground objects while front tilt will not. I use front tilt in 4x5 most of the time unless I am trying to exaggerate foreground objects. With 8x10 I find that I cannot reach the front standard much of the time so I use more back tilt as a matter of practicality.

[Rick Tardiff]

I just want to once again thank everyone for their patience and advice. I have been putting the advice to good use and I wanted to attach my latest effort. I was also trying to get to grips with instant film. but as you can see I am doing much better with focus.
ebony RW45, 210mm Rodenstock, F11@1/125 on Fujifilm FP-100B45

Thanks

[Brian Ellis]

It isn't just a matter of focusing correctly, it's also a matter of selecting the optimum aperture, which is the aperture needed to provide the depth of field you want while keeping the effects of diffraction and distortions to a minimum. The method of doing that is very easy. Attach a millimeter ruler somewhere on the bed of your camera such that you can see how many mms the front standard moves as you move it forwards and backwards to focus (or the back standard, if you're focusing with the back but I'll assume you're using the front). Many cloth or plastic tape measures have inches on one side and mms on the other and they're easy to find at a fabric store or a hardware store.

After attaching the mm scale (I used double-sided Scoth tape) focus on the nearest object in the scene that you want to be sharp in your print, note the position of the front standard relative to the mm scale, then focus on the farthest object you want to appear sharp and note the position of the front standard. Set the front standard half way between the two points and also note how far in mms the front standard traveled in moving between the two points. Consult a depth of field table that you carry around in your back pocket to see which aperture is the optimum aperture to use based on that distance. If you're using movements do all of this after you've made the movements, i.e. get everything as close to being in focus as you can first, then focus on the nearest object you want to appear sharp and the farthest you want to appear sharp, set the front standard midway between the two points, etc. etc.

If you don't have a depth of field table available there's a simple method of doing it by memory. If the front standard moves approximately 1.6 mms use f16, if it moves approximately 2.2 mms use f22, if it moves approximately 3.2 mms, use f32, etc. If you want to be extra safe stop down one additional stop.

This is one of those things that sounds a lot more complicated when explained than it is when you do it. It's a very simple and pretty much foolproof method of both focusing and setting the optimum aperture. IRC it's the same method that's explained much better and in greater detail in Tuan's article on focusing the view camera that's referred to in Jacque's message.

[Leonard Evens]

Both your examples probably require some front tilt in order to get everything in focus.

Let me tell you how I would do it.

I would choose a near point and a far point, focus on each and note the positions on the rail. Measure the distance in mm between those positions and multiply it by 5. That gives you an estimate of what you will have to stop down to in order to get everything in focus without a tilt. My guess is that you will have to stop down so far that the requisite time will be too long for acceptable subject motion and in addition at f/45 and f/64 diffraction may become an issue.

If that is so you need to til.

Let me first address the second picture. In that, everything of interest lies in or very close to a single plane stretching from the near foreground to the far background. As above choose a near point and a far point in that plane. Choose an initial tilt, say about five degrees. Then focus on the far point and refocus on the near point. If you have to increase the distance between the standards to focus on the near point, increase the tilt. If you need to decrease the distance between the standards to focus on the near point, decrease the tilt. Repeat this process until both near point and far point, and indeed the entire scene is all inf focus. At this point you can take the picture at any convenient aperture, say f/16.

Let me next address the first picture. Here not everything of interest lies in a single plane. Choose a near point on the ground in the foreground and a far point halfway up the trees in the background. Use the procedure outlined above to tilt so the plane through those points is in focus. Now consider points above and below that plane which you also want in focus, e.g, the top and bottom of the trees. Focus so that the top comes in focus , note the position on the rail, and then do the same thing with the bottom in focus. Measure the displacement between those positions, and again multiply that by five. That should give you a good estimate of how far you have to stop down to get everything in focus.
But you probably should stop down an additional stop to be sure.

The basic fact used in the second example is that when you tilt, the region of focus forms a `wedge' shaped region lying between an upper plane and a lower plane, with both these planes passing through a common line (called the hinge line) below the lens. Thus the region in focus is quite narrow close to the lens but opens up progressively as you move away from the lens. The plane of exact focus also passes through the hinge line and cuts the full region in half in the sense that any vertical section between the upper and lower plane is bisected by it.