Focus scales for Chamonix O45 F-2

C

Collas

Popular Poster
Registered User
Joined
Aug 15, 2016
Messages
109
I picked up this link from a posting on the "Large Format Photography Group" on FaceBook. Alex Burke has created a pdf template for various focusing scales for the Chamonix O45 F-2 for printing on Avery sticky labels. I haven't tried it yet, as I have the F-1 model and no labels to hand, but it does look interesting.

www.alexburkephoto.com

Focus Scales for Large Format Cameras — Alex Burke Photography

Learn the easiest method to focus any large format camera or lens. Download my focus scale template and stick it onto your film camera.
www.alexburkephoto.com www.alexburkephoto.com
 
I pinched the idea from Alex Burke's webpage and made my own scales using a Brother P-Touch tape labelling printer at work. The tapes come in various widths (I used 6mm black on white) and have the advantage of being immune to just about any solvent or water so once stuck on they stay. I put them on both sides of my Shen Hao PTB45 and they work really well. You just need to make sure 1mm on your printed scale does equal a true 1mm comparing it to a good ruler.

Just focus on the nearest and furthest parts of your image that interest you and apply his corrections. Works for me, I use it all the time.
 
The same. What do you need to be in focus? Focus to those extremes and see what the distance is. Anything over 10mm then either accept that it will be out of focus or recompose your image to get the best result.
 
Terry Jones said:
The same. What do you need to be in focus? Focus to those extremes and see what the distance is. Anything over 10mm then either accept that it will be out of focus or recompose your image to get the best result.
Click to expand...
Wouldn't the DOF requirement be less if you used tilts?
 
First of all, I would suggest you read the article on his website - it will answer many of your questions. Secondly, I rely on stopping down to the calculated f-stop and checking the image. The ground glass doesn’t lie, if it‘s in focus then that’s all there is to it. it works for any lens as well.
 
Terry Jones said:
First of all, I would suggest you read the article on his website - it will answer many of your questions. Secondly, I rely on stopping down to the calculated f-stop and checking the image. The ground glass doesn’t lie, if it‘s in focus then that’s all there is to it. it works for any lens as well.
Click to expand...
First reagrding tilting nd his calculation: He gives two example - one without tilt and one with tilt. He uses the same calculation to determine aperture setting. Why? Would the calculation be different if you're tilting?

Second: what CoC is he basing his calculations on? The "acceptable" DOF changes depending on which CoC you use.
 
I can’t answer your questions as I don’t know the answers. I am more interested in taking photographs than the minutiae of circles of confusion and acceptable depth of field.

All I know is it works for me. Perhaps there are others with more knowledge regarding this subject.
 
Terry Jones said:
First of all, I would suggest you read the article on his website - it will answer many of your questions. Secondly, I rely on stopping down to the calculated f-stop and checking the image. The ground glass doesn’t lie, if it‘s in focus then that’s all there is to it. it works for any lens as well.
Click to expand...
The scale and adjustment of the f stop is when there's no tilting according to ALex website. Other's above suggest using the scale with tilting as well. Very confusing.
 
Alan Klein said:
The scale and adjustment of the f stop is when there's no tilting according to ALex website.
Click to expand...

Alan, Mr. Burke described "focus spreading" working fine with both non-tilt and tilt in the bottom of his article.
Me I would prefer the fs method for cameras with movements only.

Personally I don't agree with some points in this article.

I have a different view on the phenomenon of diffraction.
In my understanding diffraction eclusively depends on the aperture's diameter size instead of pure aperture numbers.


""Think of a forest scene, or any landscape with a tall object running vertically through the frame.
For these scenes we need to use hyperfocal focus, where we focus somewhere in between near and far and stop down to achieve a full depth of field.
The focus spread method will allow us to focus in exactly the right spot and choose the correct aperture. ""

The focus spread method which to me is more a focus finder than a focus spreader has nothing to do with the hyperfocal focus method.
As described by Mr. Burke himself focus spreading will allow focusing in the right spot ( for being more precise this are two spots).

If something is able to "spread" the focus than it is the hyperfocal technique, there focusing to only one (mostly near) spot and in this way determining the max. sharpness range of acceptance.

Tilting a lens also doesn't mean spreading the focus but Mr. Scheimpflug found every thing along the focal plane going from near to far instead of from top to the bottom being sharp if the lens is tilted.
Bringing a far point and a near point in sharpness with the focus "spreading" method means that everything between this points will give us a sharp focal plane and is exactly what we need.
No circles of confusion necessary.

To avoid further confusion we really need another title for this technique; eventually it's a focal plane finder technique but has nothing to do with spreading anything.

Best,
Reginald
 
Tilting would be significant if the camera uses base tilt. Base tilt moves the lens and the camera must be re-focussed. Consequently the tilt must be applied before the scale is used. With centre tilt, we are assuming that the lens remains in much the same place, but this depends on the precise construction of the camera.
Much of the usefulness of this system depends on a careful choice of the two points of focus. Sometimes there may be no convenient physical object at one or other of the chosen distances.
It might be sensible to remember that there is no such thing as “depth of field”. It’s a convenient fiction. There’s sharp focus in one plane and an acceptable lack of sharpness that diminishes away from that sharp plane. “-Acceptable” will vary. This is where the idea of a circle of confusion comes in. What do we consider to be acceptable? Clearly, a contact print viewed at a distance will be more tolerant of imperfect sharpness that an enlargement viewed from the length of a nose. Even the paper used for printing will have an effect. Rough watercolour-type paper will be less demanding than smooth and glossy.
Although it seldom happens in LF, we might use the same process to determine what is out of focus - the digital photographer’s bokeh.
In actual practice, I’ve found that muscle memory works well enough. Grip the focus knob in a convenient way. Rotate it to one point of focus. Now, without changing your grip, rotate to the other. It’s now easy enough to turn back your wrist to the halfway point. All done under the dark cloth with the screen in full view all the time.
 
David M said:
Tilting would be significant if the camera uses base tilt. Base tilt moves the lens and the camera must be re-focussed. Consequently the tilt must be applied before the scale is used. With centre tilt, we are assuming that the lens remains in much the same place, but this depends on the precise construction of the camera.
Much of the usefulness of this system depends on a careful choice of the two points of focus. Sometimes there may be no convenient physical object at one or other of the chosen distances.
It might be sensible to remember that there is no such thing as “depth of field”. It’s a convenient fiction. There’s sharp focus in one plane and an acceptable lack of sharpness that diminishes away from that sharp plane. “-Acceptable” will vary. This is where the idea of a circle of confusion comes in. What do we consider to be acceptable? Clearly, a contact print viewed at a distance will be more tolerant of imperfect sharpness that an enlargement viewed from the length of a nose. Even the paper used for printing will have an effect. Rough watercolour-type paper will be less demanding than smooth and glossy.
Although it seldom happens in LF, we might use the same process to determine what is out of focus - the digital photographer’s bokeh.
In actual practice, I’ve found that muscle memory works well enough. Grip the focus knob in a convenient way. Rotate it to one point of focus. Now, without changing your grip, rotate to the other. It’s now easy enough to turn back your wrist to the halfway point. All done under the dark cloth with the screen in full view all the time.
Click to expand...
But how do you do both tilt and
Center focus? After you've applied all of the adjustments for tilt, are you supposed to then find the far and near focus points and center the knob? That takes the whole tilt process and throws it away
 
Before using a large format camera, I always found the focus spread for depth of field by focusing in a third of the way between the range of the depth of field.
Use of a depth of field chart or the depth of field ring on some lenses are also used to find the right Focus point.
 
Like many things in LF, I think you have to go round and round, doing the same things, until you end up with an acceptable compromise. A bit of juggling. The compromise may involve stopping down a bit more. The advantage of this is that diffraction may then reduce the perfection of the sharpest parts. Deprived of an absolute standard of sharpness, the rest of the image now looks better.
A counter-intuitive result, I know. If you’ve looked at a body of pinhole work, you’ll know how the eye adjusts its expectations and no longer sees the overall lack of perfectly defined edges.
For a more numerate approach, see Harold Merklinger, now available as a PDF for download. His methods involve calculation in the field. He deviates from convention by answering the question: “What detail do we want to resolve in the scene?” The conventional approach is concerned with resolution at the film plane.

Giving numerical limits for DoF can be deceptive. There is no boundary where sharpness undergoes a perceptible change.
 
David M said:
Like many things in LF, I think you have to go round and round, doing the same things, until you end up with an acceptable compromise. A bit of juggling. The compromise may involve stopping down a bit more. The advantage of this is that diffraction may then reduce the perfection of the sharpest parts. Deprived of an absolute standard of sharpness, the rest of the image now looks better.
A counter-intuitive result, I know. If you’ve looked at a body of pinhole work, you’ll know how the eye adjusts its expectations and no longer sees the overall lack of perfectly defined edges.
For a more numerate approach, see Harold Merklinger, now available as a PDF for download. His methods involve calculation in the field. He deviates from convention by answering the question: “What detail do we want to resolve in the scene?” The conventional approach is concerned with resolution at the film plane.

Giving numerical limits for DoF can be deceptive. There is no boundary where sharpness undergoes a perceptible change.
Click to expand...

You have to use some guideline. Otherwise do you pick F/4 or F/22?
 
I think you’ve put your finger on it - guidelines. It’s f22 for me every time. I envy you your f4 LF lenses.
This isn’t quite the same subject. This is deciding how much depth of field you want, rather than where it’s placed.

Have a look at Merklinger. He gives much more precise answers than my own “…keep on doing it…”

I must confess that after reading him, I decided that the ground glass is king. His earlier work, The Ins and Outs of Focus is also interesting.
 
David M said:
Tilting would be significant if the camera uses base tilt. Base tilt moves the lens and the camera must be re-focussed.
Click to expand...

If you like to focus first, later tilting the lens needs re-focusing, yes.
The other way, described by Mr. Schoen for his Linhof papers or by Mr. Merklinger using the full Scheimpflug rules ( "hinge rule"), takes the lens in place first.

Alan Klein said:
But how do you do both tilt and
Center focus?
Click to expand...

To me the focusing method depends on subject and distances, the operation depends on the camera.
My long gone Shen Hao HZX 45 II has absolutely been my fastest camera.
It was so easy to tilt the lens in each directionand simultaneous doing the bellows movements.
Saying this I have found nearly the same with old Plaubel rail cameras.
Only the groundglass and fresh eyes have been the controlling elements.

My Reisekameras and the Mentor Studio need more patience and doing things step by step.
Best way outdoor to me then is setting the tilt degree first.
Alan Klein said:
You have to use some guideline. Otherwise do you pick F/4 or F/22?
Click to expand...


The guidline could be " if avoiding stopping dow too far is needed, Scheimpflug comes along".
This rule isn't only for wide sharpness in the field but good for more open apertures, too.

The choice of using f4 or f22 to me is an artistic question.
I can't imagine stopping down my SF lenses.
Vice versa for overall sharp landscapes.

David, speaking with now retired master professionals they never heard much or cared less about COC or resolution of film or MTF curves.
I have heard statements like "I have had to photograph, I haven't the time for technicals discussions.
Great:)
They made huge enlargements some meters long, enlarged in old cinemas.
Of course they knew about the lack of sharpness but who cares if the print is hanging on a skyscraper.

Obvisiously if we need the best results we have to go more to the depth using math for tilting and focusing, CoC formulas and slow film with high resolution.
All depends on the size of the enlargement and of the viewer's distance.

How difficult to handle all steps from film choice and lens choice over film flatness to focusing right, exposure and development and finally managing enlargement influence will be shown from large enlargements.
This could start with a print of 20x24".
 
You must log in or register to reply here.
Back
Top