How to obtain enough depth of fieldgreenspun.com : LUSENET : Large format photography : One Thread
I've been shooting with my Toyo 4x5 for about a year now and I love it. Unfortunatley, some of us don't have mechanical depth of field calculators built in to our view cameras and that's where the frustrations begin.
I purchased Rodenstocks View Camera calculator, it helped some because your focusing on two points and it then chooses for you your optimal f/stop. I need more info!!!!
So, assuming the cameras level, tilt,swing,shift all set at 0 deg, and you just dropped your Rodenstock calculator in the lake, where would you go from there? Should I give up and set everything to f45.
Rodenstock also claims you should set your focus point to half the distance between to objects, instead of the first third I always assumed was correct. If anyone out there has been through this stage in there photographic journeys and could shed some light, or shall we say-some depth of field on the subject,I would truly appreciate it.
Thank you for your time,
-- Albert Martinez (email@example.com), July 21, 2000
Albert: Go the the Schneider Optics web site and they have listed the depth of field charts for their lenses, listed by focal length. It doesn't matter who made your lens, focal length and f-stop determine depth of field. You can figure hyperfocal distance from these charts. Rather than depending on extras like depth of field calculators, I would study the ground glass and get everything sharp as possible with a loupe, then stop down until everything appears sharp, then go one stop more. It will make your LF work much faster and more pleasant. With swings and tilts, you can tailor the depth of field for your LF lenses to match the subject you are shooting.
-- Doug Paramore (firstname.lastname@example.org), July 21, 2000.
react to your gg thats were the magic happens
-- lee nadel (email@example.com), July 21, 2000.
There is a technique that was beautifully described in an article in Photo Techniques a couple years ago that I think will help. It involves taping or gluing a mm scale to the focusing bed and observing the exact point at which the nearest and furthest subjects come into focus with respect to a mark you can make on the front standard or other moving part of the focusing mechanism. The difference or focus spread determines the aperture you'll need to achieve acceptable sharpness. You simply place the front standard smack in the middle of that range, set the lens and expose your film. I don't remember the exact issue this appeared in, but I 've been using this technique for at least two years with great success. It also allows you to use swings and tilts and any focal length of lens. Hope it helps.
-- Robert A. Zeichner (firstname.lastname@example.org), July 21, 2000.
My answer: don't drop the Rodenstock calculator in a lake.
Robert Zeichner's method works on the same principal (determining aperture from the amount of movement of the standard on the focusing rail necessary to get near and far points into focus). You can calculate a factor (either by experience or working backward from the Rodenstock calculator) by which you multiply the amount of movement in mm on the rail to get the right aperture. The Rodenstock calculator gives you the additional ability to refine this calculation when the focusing rail is not level or when you are doing close-up work (both of which allow a larger aperture for the same amount of movement on the rail).
Personally, I find DOF tables extraordinarily unhelpful in practice. The method you are using is much easier.
-- Chris Patti (email@example.com), July 21, 2000.
One last thought: Anyone who can tell whether the image is sharp when the lens is stopped down to f/45 has a much better ability to see in the dark than I do.
-- Chris Patti (firstname.lastname@example.org), July 21, 2000.
I don't think using depth of field calculations in object space is a good idea with the view camera. First, unlike on helicoidal-mounted lenses used on rigid cameras, you don't have a focussing scale indicating at what distance your lens is focussed, neither do you have a depth of field scale. Second, tables can be used only when the standards are maintained parallel. Third, why use a method based on guessing, when you can fairly easily use an exact method ?
For several years I have relied on stopping down the lens and inspecting the ground glass. I eventually found that this yielded results less sharp than I wanted. The problem is that it is not that easy to make a good judgement of sharpness on the ground glass. The image is grainy, and when you stop down, the image on your ground glass gets pretty dim. The magnification depends on the lupe you use.
The idea to relate the focus spread to depth of field was first implemented by Sinar in their cameras. As their patent ran out, other manufacturers, including Arca-Swiss came up with a similar device. Articles which explain in detail how to use the relation in practice include a draft by Guy de Riencourt, Depth of field and the view camera, the article by Joe Englander, Apparent Depth of Field: Practical Use in Landscape Photography, and the article by Stephen Peterson, Image sharpness and focussing the view camera, Phototechniques March/April 96.
The idea of combining the effects of diffraction and defocus to find the optimal f-stop was explained by Paul Hansma in the article View camera focussing in practice, Phototechniques March/April 96. This method seems to make the most sense to me and the article will be available soon on the LF page, courtesy of Paul Hansma. However, Paul Hansma's use of N/750 has been criticized by Bob Wheeler, in his Notes on view camera geometry, section 9.3, where he said it should be N/1500. I am still trying to understand clearly the issue, before writing an article on depth of field for the LF page.
-- Q.-Tuan Luong (email@example.com), July 21, 2000.
I don't believe the Rodenstock calculator tells you to focus at the half-way point between the near and far points. If I remember, it tells to to set the rear standard 1/2 way between the near and far points. For middle distances, this point on the rail approximately equates to the 1/3 - 2/3 rule in object space. The 1/3 - 2/3 rule does break down at the extremes. For example, if your doing table top work, it is closer to a 1/2 - 1/2 rule.
My advice - read different articles and understand the techniques and then choose ones which work for you. For example, I'm not a big fan of the two point focusing techniques. There is nothing wrong with it; many people swear by it. When shooting interiors, I'd rather determine the distance and f-stop needed, and then focus on something at that distance. For critical work, I use Bob Wheeler's Vade Mecum program and PCAM on the Palm Pilot to calculate these parameters (and others).
-- Larry Huppert (Larry.Huppert@mail.com), July 24, 2000.
DOF is really only half the problem. You will have a difficult time getting the sharpness you want if you do not get the best plane of focus to begin with.
Someone posted that you should react to your ground glass. I really agree with this philosophy. Take your camera out and play with the front and rear tilts and swings. Make notes on what points come into focus together as you adjust the swings and tilts and re-focus.
Once you are comfortable with the procedure of placeing the plane of focus to maximize sharpness in the foreground and the background, then just shoot at the smallest aperature that suits your goal for the photograph. Remember that smaller is not always better. With 4X5, if you go much smaller than f/32.5 you start to get into diffraction problems.
-- Jason Kefover (firstname.lastname@example.org), July 24, 2000.