lens quality relating to depth of field?greenspun.com : LUSENET : Large format photography : One Thread
I am shooting with a super speed graphic, which has a Rodenstock 135mm lens. Minimum aperture on this lens is F32. If I get a lens that has a smaller aperture capability, will that improve my depth of field capability? Do I need to go to medium format? Thank you- Jon
-- Jon Paul (email@example.com), October 13, 1999
Yes, it would give you a bit more DOF, at the expense of diffraction. MF wont give you more DOF. Its a function of image size on the film plane, and MF lenses dont get around the laws of physics.
-- Ron Shaw (firstname.lastname@example.org), October 13, 1999.
You need to use tilt in the front standard. That way you don't have to worry so much about the f-stop. Get a book a LF movements.
-- sheldon hambrick (email@example.com), October 13, 1999.
Tilt is of no use if the the composition near the lens has significant vertical extent. In that case, your only option is to use a smaller aperture or recompose.
But here's the bottom line, in my not so humble opinion. Too many large format photographers are overly concerned about technical details, such as achieving optimum sharpness, and forget the art that is photography. So, Jon, I'd worry first about your composition, and then do whatever you have to do in order to obtain the depth of field required. If that means stopping the lens down to f64, then so be it. IF f64 isn't enough (or in your case, f32), then you have to either recompose (i.e., move the camera) or recompose in the sense of working with a more limited depth of field.
I rarely make a landscape image at less than f32, unless I am intentionally trying to work with limited depth of field. Usually, I'm in too much of a rush because of fading light to take the time to find the optimum aperture. So I often just dial in f45 (f32 if I've used tilt), check for problem areas, and if there are none, click the shutter. Is there diffraction - yes. But it's minor at most scales of enlargement, especially when compared to the potential lack of depth of field when I need it.
The Aquarium of the Americas just purchased a 30x36 copy of an image I made with a 90 mm fuji lens at f45-f64. I didn't hear anyone comment about diffraction. Their purchase was based on the composition.
I'd strongly recommend that you purchase a 135 mm f5.6 which usually have a minimum aperture of f64. I have the Rodenstock S series which is a bit more expensive than the N, but gives you a larger image circle and better flare control. I love it.
Best wishes, Bruce
-- Bruce M. Herman (firstname.lastname@example.org), October 14, 1999.
Hi, Bruce: For a vertical subject, you use the "swing" or vertical rotation. For a horizontal subject, you use the "tilt" or horizontal rotation. This way, you do not need to use a small aperture. Make sure your camera is "yaw free" if you apply both movements at the same time. It really makes life easier. I just use medium apertures when the subject is on the same plane. Best, Tito.
-- Tito Sobrinho (email@example.com), October 17, 1999.
Jon, One of the advantages of getting proficient with the use of movements is the ability to reduce the amount of depth of field you will need for a given scene. Of course there are instances when any such movement will not result in a bit of help such as views where there are tall trees in the foreground that you want to be as sharp as the mountains in the background. What will help in all instances is learning how to set focus in the correct plane. There's a very helpful technique I learned from an article in PhotoTechniques magazine that makes this easy. You tape or glue a millimeter scale to the focus bed and scratch a witness mark on the moving rail. You focus on the furthest object you desire to be sharp and note the place on the scale that the mark lines up with. You then focus on the nearest subject and make a similar note. You then place the mark exactly in between and note the spread, in millimeters. Here's where you'll have to search for the article to get the value chart. But, essentially, you look up the spread (Delta) and see what aperture is indicated to bring all subjects in that range into acceptable focus. This technique not only allows you to know where to focus and what aperture to use, but it tells you if it is even possible to get sharp results. What's neat about this is that you can mess around to your heart's content with the movements and the system still works (although you may need to more carefully observe the nearest and furthest focus points as these can change radically when you start to tilt and swing). Note that the minimum recommended apertures for various large formats are: 4x5=f32, 5x7=f45 and 8x10=f64. These are just guidelines and not law. I've made many exposures in 4x5 at f45, for instance, with good results. This is a very brief explanation which I hope will get you started in finding your own personal technique for achieving the results you desire. There are many other opinions and methods for dealing with this, but having tried this and gotten consistantly good results, I thought it would be of help to you. Good luck. BZ P.S. I agree with one of the other respondent's comments about art being overwhelmed by technique, but I strongly believe that all artists need to master their tools and make their use second nature so as to be able to achieve any result that artist desires. A musician must master the scales and chord intervals etc. to be able to compose his or her own music!
-- Robert A. Zeichner (firstname.lastname@example.org), October 18, 1999.
Robert - I was with you all the way until the part about the "recomended minimum aperture" being F32 for 4x5. I studied the same articles you're talking about and have been using the method described in them on two different cameras with good results for about three years now but I don't recall anything about a recomended minimum aperture. One of the good things about using the system the authors discuss in the articles is that you actually get the "optimum" aperture, "optimum" in this case being that aperture which will give you both the necessary depth of field, based on the distance between the near and far focus points, and that will also produce minimum diffraction. If all we ever wanted was maximum depth of field we'd all just stop down to F64 every time and be done with it. We don't do this of course, in part because of diffraction. So I thought the real benefit of using the method outlined in the articles was the fact that you end up with the necessary depth of field and also with the minimum diffraction. In some cases, when the distance between the near and far focus points is very small (say a mm or so) the aperture that you end up with if you use the method discussed in the articles is something like F 11 or F 16. Anyhow, I was just curious about this "minimum recomended aperture" business - recomended by who and for what purpose? Brian
-- Brian Ellis (email@example.com), October 22, 1999.
It is a well known fact that all major brands (Schneider, Rodenstock, Nikon and Fuji !!) in their illustrative material advice (apart from special models like process lenses or Imagon) an aperture of 22-32 as ideal from a lens constuction point of view, below and above the results are affected by things like diffraction and other optical abberations. If we see this as scientific results they are for sure explainable and true on the other hand, any form of printing or reproducing a slide or a negative will affect the results a lot more then refined optics can do.
-- andrea milano (firstname.lastname@example.org), October 23, 1999.
I goofed! By "minimum recommended aperture" I really meant smallest recommended aperture. In other words, an aperture smaller than f32 for 4x5, as an example, might result in visible diffraction artifacts. Naturally, the degree of enlargement must be factored in as well. Sorry if I confused anyone.
-- Robert A. Zeichner (email@example.com), October 23, 1999.