stopping down for focus

[JPlomley]

How practical is Joe Englanders suggestion for biasing infinity focus when no movements are involved? For example, let's imagine you have a 2mm focus spread. We would setthe focus point either 1/3 back from infinity or 2/3 forward from close-focus in order to bias focus for infinity (focussing with the reard standard). Putting this into real measureable numbers on an Arca Swiss monorail, this is pretty tough since increments are in 1mm. So 2/3 forward from close focus for a 2 mm spread would be 1.3mm. My rail is just not this accurate. So I question the practicality of the technique. Would it not be more practical to use the grids on the groundglass?

[Paul Metcalf]

Actually, you do. Check this out: http://www.largeformatphotography.info/fstop.html.

And this article mentioned in the aformentioned page: http://www.englander-workshops.com/documents/depth.pdf

1/2 way in image space, that's theoretically correct. And that corresponds to approximately 1/3 in scene space for non-high magnification situations.

[Vaughn]

The method I teach, and it worked in my recent Monterey workshop, is to have the student focus so that the closest objuct of interest and the farthest object of interest are equally out of focus. Then, as they close down, the dof lines spread equally near and far so that these two objects are brought into the dof area at the same f-stop. This is after all best efforts with movements are done.

One of the mantras I teach is "The groundglass is truth." If you really learn to study and look at the gg you won't be fooled.

steve simmons

Pretty much what I tell our students...especially the last bit. Since judging if the close and far objects are "equally" out of focus can be difficult, I tell them to close down the lens and see if the close and far come into focus at the same time. If, for example, the far comes into focus first, then refocus a little closer and try again.

I also suggest that once they find an fstop where everything is in focus, to close down one more fstop, since the lens is probably sharper than one's eyes.

I like this practical WYSIWYG approach for beginners. Then if they are interested, they can explore other methodology.

Vaughn

[Los]

thank you everyone for your help. as brian suggested, the "fuzziness" is over the entire image. i usually shoot at apertures between f8 and f16 on fuji 160s. i had an 8x10 made from a flatbed scan, but i'm basing my observations from viewing the negative on a light table with a toyo groundglass loupe. the largest i intend to print in 20x24. here are my notes from the test:

135mm
f45.3 @ 1/8th sec
w/ polarizer
focus spread 4mm
recommended stop f32.6
focus is from the foreground white fence to facade of house across the street.

the picture attached if from a 600dpi scan at full size, cropped, and unsharpened. given the softness of the flatbed scan, i think you can still see where the details on the suv (about center on the focus spread) are much sharper than the fence in the foreground.

i am wondering if this can be made to "appear" sharper by plus development, scanning and USMing. or am i print sniffing at this point?

[steve simmons]

You have way too many variables here.

1. this is a print from a scan. How good is the scan?

2. Why are you shooting at f8-16. LF lenses are generally, and this is an over generalization, better in the 16-45 range.

The problem may or not be the lens and/or the negative.

Your problem could be dof. What do you nean when you say the focus spread is 4mm???

Before you can get any helpful advice you need to go back to the basics and stop combining apples and bananas.

steve simmons

[Los]

You have way too many variables here.

1. this is a print from a scan. How good is the scan?

you're seeing the scan from the neg. not a consideration. a quick a dirty proof.

2. Why are you shooting at f8-16. LF lenses are generally, and this is an over generalization, better in the 16-45 range.

i like resolution and sharpness, both are better wider on the stop. dof is the tradeoff.

The problem may or not be the lens and/or the negative.

never said there was a problem. systems' fine. just trying to adjust one aspect to my liking.

Your problem could be dof. What do you nean when you say the focus spread is 4mm???

my micro focusing bed has a scale in mm. near focus at -4mm, far focus at 0. spread 4mm.

Before you can get any helpful advice you need to go back to the basics and stop combining apples and bananas.

i'll have you know, it was apples and grapes!

steve simmons

[Brian Ellis]

I can answer one of your questions. Plus development affects contrast, it won't affect apparent "sharpness."

In response to Steve's question of why you were shooting at f8-f16, you said "I like resolution and sharpness, both are better wider on the stop. dof is the tradeoff."

There are a couple misconceptions reflected in this response but the main one is your apparent thought that it's better to have good "resolution and sharpness" than adequate depth of field. I assume, in view of your original question, that you're thinking the effects of diffraction will adversely affect the "sharpness" of the photograph if you stop down below f8-f16. If that's the case then in my opinion your thinking is wrong. The effects of inadequate depth of field will almost always be far more apparent than the effects of diffraction when using 4x5 or larger film and making an enlargement in the 4x-5x range. In general, it's much better to have the depth of field you need to make the photograph you want to make than it is to worry about diffraction when using 4x5 and larger film.

Unfortunately I can't really figure out what's going on from the image you posted. On my monitor the entire image looks fuzzy. In other words, it looks like you didn't get anything in focus. If that's how it really looks then you just aren't focusing your camera properly. A very good place to learn how to focus a LF camera is the first article that David cited in his response to your original question. Steve Simmons' method will certainly work too but I'm not sure it's the best method for a beginner because I think it takes some experience to be able to tell by looking at the ground glass when two things are equally out of focus. But you could give it a try if you like and see if it works for you.

[domenico Foschi]

What Kind of lens were you using?
It seems to me that there is a lot of perspective compression in the image as if you used a tele lens.

[David Millard]

To me, it looks like the overall blur may have as easily resulted from camera shake due to an unstable tripod/head, apart from any optical issues from your lens.

[Dick Hilker]

Steve, you mentioned, "I am also a fan of the gg brighteners as most of them will brighten the image by 2 stops."

I tried to find some info about this, but came up with nothing: what do you suggest?