Focus Advice

[Ryan Grayley]

I recently acquired a Shen Hao clone of the Ebony 45 SU and I am hoping that someone can help me with a (probably) stupid question...

Until now I have been spoilt by the depth of field calculator on my Sinar F1 but my Shen Hao doesn't have this luxury.

So what procedures do all you good people use to ensure a good spread of focus? I have read about how some people stick masking tape to the sides of their field cameras and then place marks at the far and near focus points. This can then be used to determine the focal point and aperture etc.

Sorry if I am being stupid but any advice would be great!

Thanks,

Ryan Grayley

[Joanna Carter]

Hi Ryan and welcome to the funny farm

Although you can use straight forwards depth-of-field focusing, the majority of people seem to use movements to achieve full-frame focus.

This is usually achieved by applying a bit of tilt or swing to the front standard. However, getting the right degree of tilt/swing can cause a lot of head scratching and frustration.

The most important point to realise is that calculations cause headaches; empirical (suck it and see) adjustments are much easier and quicker.

For the most common scenario of wanting everything in focus for a landscape like this :



... you would basically apply a little forward tilt (the angle isn't important); this will give you the "stripe" of focus necessary to start adjusting.

Then focus on the foreground using the rear standard focus adjustment.

Now you will need to adjust the degree of tilt of the front standard to try to focus the horizon. This will put the plane of focus from under the camera, through the sunflowers in front of the camera, to the horizon. This is best achieved by applying small iterative adjustments to both the tilt on the front standard to focus the horizon, and the focus on the rear standard to focus the foreground. Do not try to achieve perfect focus on both horizon and foreground in one movement; this only rarely happens in the case of very small tilt requirements. Instead move either the tilt for the horizon or the focus for the foreground, until the focus improves and then go back to the other adjustment and re-adjust that to maintain focus there as well.

In the case of this example shot, due to the height of the sunflower heads in front of the camera (4ft), or if the scene contains objects of a certain height, you may not get everything in focus until you stop down to a smaller aperture, this is normal and is a factor of the angle not giving sufficient depth of field. However the depth of field is like a wedge with its point under the camera, opening out as it gets further away from the camera.

Beyond all doubt, the most important piece of information I gleaned is that the angle of tilt required can be extremely small, sometimes less than half a degree!! Take a look at these articles for some very useful and not too technical information on how Scheimpflug works; pay special attention to the tables at the end of the article that show the degree of tilt required to achieve, what can be, virtually, a 90 degree field of focus.

http://www.trenholm.org/hmmerk/SHBG09.pdf

http://www.trenholm.org/hmmerk/VuCamTxt+.pdf

Does this help or confuse ?

[Paul Sanders]

have to say I struggled with the whole focus issue until the last workshop when Joanna showed me a test with a chess board - brilliant and simple - but now I do undertstand exactly about using the camera movements.

[Ryan Grayley]

Thanks Joanna. The technique you describe for Scheimpflug on these field cameras seems quite different to my experiences with my Sinar F1. The F1 has a focus and Scheimpflug calculator built in which makes it very easy in the studio.

Anyway, I have bought three packs of 5x4 b&w Polaroid so I have no excuses now! I will give your methodology a try and perhaps I will update this thread with my results. Incidentally, my initial experiments will be tableaux similar in style to Hannah Starkey rather than straight landscape but hopefully the techniques will be transferable.

Any tips from other members?

[Apple]

Ryan,

I know what you mean about the Sinar depth of field dial as I have a P2 and it's a luxury you miss when moving to other things (like asymmetrics and angle markings but I half got round that that by buying an SU model)

Joanna's method does work - have a practice with it. Only commit it to polaroid / film when you're happy with it on the ground glass. After a while you start seeing things in planes of focus (sad, I know but heyho, that's the part of the LF bug... )

Because you're dealing with a wedge of sharp area, you might put the plane half way up a mountain or tree in the distance and half way through the rock in the foreground - as you stop down the lens, you see the picture get sharper as the focus area fans out either side of the plane to cover the top and bottom of the tree, mountain etc. Think of it as pointing your middle finger along the plane of focus and then spreading your index and third fingers - this is the area of "sharp" focus expanding as you stop down.

As you probably know, playing with the movements on the front standard alters the plane of focus, using the rear standard alters he focus plane and the perspective of the picture.

Andrew

[Apple]

PS it's easier if you have three hands so you can tilt the front, focus the rear standard and hold a loupe to the ground glass all at the same time...

[Keith Tapscott]

Hi Ryan and welcome to the funny farm

Although you can use straight forwards depth-of-field focusing, the majority of people seem to use movements to achieve full-frame focus.

This is usually achieved by applying a bit of tilt or swing to the front standard. However, getting the right degree of tilt/swing can cause a lot of head scratching and frustration.

The most important point to realise is that calculations cause headaches; empirical (suck it and see) adjustments are much easier and quicker.

For the most common scenario of wanting everything in focus for a landscape like this :



... you would basically apply a little forward tilt (the angle isn't important); this will give you the "stripe" of focus necessary to start adjusting.

Then focus on the foreground using the rear standard focus adjustment.

Now you will need to adjust the degree of tilt of the front standard to try to focus the horizon. This will put the plane of focus from under the camera, through the sunflowers in front of the camera, to the horizon. This is best achieved by applying small iterative adjustments to both the tilt on the front standard to focus the horizon, and the focus on the rear standard to focus the foreground. Do not try to achieve perfect focus on both horizon and foreground in one movement; this only rarely happens in the case of very small tilt requirements. Instead move either the tilt for the horizon or the focus for the foreground, until the focus improves and then go back to the other adjustment and re-adjust that to maintain focus there as well.

In the case of this example shot, due to the height of the sunflower heads in front of the camera (4ft), or if the scene contains objects of a certain height, you may not get everything in focus until you stop down to a smaller aperture, this is normal and is a factor of the angle not giving sufficient depth of field. However the depth of field is like a wedge with its point under the camera, opening out as it gets further away from the camera.

Beyond all doubt, the most important piece of information I gleaned is that the angle of tilt required can be extremely small, sometimes less than half a degree!! Take a look at these articles for some very useful and not too technical information on how Scheimpflug works; pay special attention to the tables at the end of the article that show the degree of tilt required to achieve, what can be, virtually, a 90 degree field of focus.

http://www.trenholm.org/hmmerk/SHBG09.pdf

http://www.trenholm.org/hmmerk/VuCamTxt+.pdf

Does this help or confuse ?

Ole pointed out about `Merklinger`s Hinge Rule` to me. From the same site, a 146 page PDF can be downloaded called `Focusing The View Camera`.

http://www.trenholm.org/hmmerk/FVC16.pdf

If this is mentioned else where on the forum which I haven`t found, then my sincerest apologies.