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Aaron Svenby
11-Jan-2010, 13:49
Greetings all you fellow Linhof shooters.
I have the Linhof 617 S III with Schneider 180mm lens, and I am somewhat new to the large format world.
I am having difficulty understanding the depth of field for this lens....and have wasted more film than I want trying to figure it out. I think I was given wrong info on how to focus the lens.
So here is my question....
If you set the F-stop to say F22 (for this example) and you look at the depth of field preview on the lens it will tell you that you should have something like infinitely to like 40feet in focus right?
So...where would you set the actual lens focus ring to obtain infinitely to 40feet?
Do you set the focusing ring where the infinitely sign would be on the right f22 marker and the 40ft sign would line up with the left f22 marker and the center triangle in in the middle of 40ft and infinitely.
I was told that you set the focusing ring where the infinitely sign is lined up with the triangle and everything from there on back is in focus....so in that case it would be 40ft?
Would love to hear from those who are experienced with this.

darr
11-Jan-2010, 15:05
It sounds like you are talking about using the Hyperfocal Distance which is the actual Focal Distance at which Depth of Field will be a maximized for a given f-stop. I do not have a Linhof 617 and Schneider lens, but I do use a Fotoman 617 with Rodenstock lens. Using this technique is so easy!! If your lens is setup with a Helical Focus mount, then follow the following info:

35478

Lachlan 717
11-Jan-2010, 15:44
Arron,

For a 180mm lens on 6x17cm, the hyperfocal distances are:

f5.6 - 47.2m (23.6m-Infinity)
f8 - 33.1m (19.4m-Infinity)
f11 - 24.1m (15.9m-Infinity)
f16 - 16.6m (12.2m-Infinity)
f22 - 12.2m (9.5m-Infinity)
f32 - 8.4m (7.0m-Infinity)
f45 - 6.0m (5.2m-Infinity)

Hope that these help!

Bob Salomon
11-Jan-2010, 16:33
I do it differently. When I want a specific DOF on the 617 system I see what my near and far points are. Pick the aperture that the scale shows covers that DOF and set it there and then stop down one more stop. So if the focusing mount shows that f22 covers the range you want set the focus mount so the near and far points are at f22 and expose for f32. I make really big prints (60" wide and up) from the 617 SIII so when I want maximum DOF I find that this is the fastest and quickest way.
Otherwise you can get the ground glass back for the SIII and the focusing loupe for the GG back and do it visually.

11-Jan-2010, 17:25
If you want objects at infinity to be critically sharp you should focus at infinity.

Using the hyperfocal distance is a compromise. Depending on how the important objects in your scene are distributed, if you're not careful, you can easily end up with pictures in which nothing actually looks very sharp.

If you are going to use hyperfocal distance, Bob's suggestion to stop down a bit further that what the markings say is a good one. But bear in mind that beyond a certain point you will lose sharpness to diffraction as you stop down further. What this point is will depend on how critical a viewer you are, how big an enlargement you're making, etc. You should run your own tests to find your comfort zone for your equipment and printing and viewing habits.

Aaron Svenby
12-Jan-2010, 00:08
Thank you to all for your replies and time!
This has helped clear up some things.
darr:
I like the image, that really helped me visualize what you where talking about.
The Schneider 180mm lens is very much like that...thanks.

Lachlan 617:
I like the chart helps simplify it. 2 questions
1. where did you get the chart from....this would be nice to know.
2. why are there 2 close numbers.....example f22 - 12.2m (9.5m-Infinity)
the 12.2m and the 9.5m (which one is it?)

Bob:
I am right there with you on the large prints.....that is why I purchase this camera.
If I set f-stop on the lens to f22 and expose for f32 wouldn't that underexpose the image....I guess I am confused on why the extra stop.

Oren:
I know what you mean about the objects at infinity appearing critically sharp. When I have tested the lens in the past and set it to infinity it is tack sharp at infinity.....and I also noticed that around f29 things seem to become a bit dull like you are saying.

All:
So one last thing to clear it all up....and hopefully take all replies into consideration.
I will use darr's picture as an example.

The image on the bottom is set at f22 and the closest(3meters) and infinity are both lined up with f22 on both sides.
So....am I to understand that the sharpest point of this lens is that center mark (red center line for the fotoman)....(or in the case of the Schneider 180mm lens the triangle)? And it will become gradually less sharp as you go out either direction from that center point to the f22 markings and eventually once I go past the f22 markings it will no longer in focus?

12-Jan-2010, 00:19
Bob:
I am right there with you on the large prints.....that is why I purchase this camera.
If I the lens to f22 and expose for f32 wouldn't that overexpose the image....I guess I am confused on why the extra stop.

What Bob meant was, if you want to be sure of having reasonable sharpness over the entire region suggested by the f/22 markings, you should set the aperture to f/32 instead. Of course, you should use your meter to determine the appropriate shutter speed to set, given an aperture of f/32.

All:
So one last thing to clear it all up....and hopefully take all replies in consideration.
I will use darr's picture as an example.

The image on the bottom is set at f22 and the closest(3meters) and infinity are both lined up with f22 on both sides.
So....am I to understand that the sharpest point of this lens is the center mark (red center line for the fotoman)....(or in the case of the Schneider 180mm lens the triangle)?

Yes.

And it will become gradually less sharp (duller) as you go out either direction to the f22 markings and once I go past the f22 markings it will no longer in focus? More or less. Actually, counting the f/22 marking as the end of the (sort of) in-focus region is based on arbitrary assumptions about what's called the "circle of confusion". If you want to understand that better, look for some reading material about how depth of field is calculated. If you just want to go out shooting for now, that's a reasonable interpretation to start with. You can follow Bob's advice if you want to be on the safe side.

Lachlan 717
12-Jan-2010, 13:58
Lachlan 617:
I like the chart helps simplify it. 2 questions
1. where did you get the chart from....this would be nice to know.
2. why are there 2 close numbers.....example f22 - 12.2m (9.5m-Infinity)
the 12.2m and the 9.5m (which one is it?)

Aaron,

1. I got this from an iPhone app called PhotoBuddy (working through each f-stop, rather from a single chart). There are many apps for photography, but I found this one recently and like it as it has a bellows compensation option (don't worry about this if you don't know what it is; not necessary with your camera).

2. Very brief explanation about focus: it isn't a 50/50 principle. In other words, you don't get 50% of DOF in front of the focus point and 50% behind; if you consider it to be a third in front and two thirds behind, you'll generally be close enough if you're guessing in situ, The numbers that I gave you work in the following way (given the example of f22 (f22 - 12.2m (9.5m-Infinity). This states that, at f22 for your 180mm lens, if you focus on a point that is 12.2 meters from the lens, your DOF will include everything from 9.5m through to infinity.

A couple of basic principles to consider/know/understand:

1. The closer the point of focus, the less DOF (less DOF when you are focused on a point at 4 meters than when you are focused at 20 meters) ;
2. The longer the lens (i.e. greater the focal length), the less DOF (a 90mm lens will appear to have greater DOF than a 180mm lens).

Hope that this clarifies things just a little...