16 MM Camera Lens Out Of Calibration? (#2)
This is the second in a series of posts. The prior post can be found here: Student Asks, Was The Lens Out Of Calibration? (#1) http://mclarenblog.com/?p=1032
On 11/18/10 9:57 PM, “A. B.” wrote:
All this information is very useful and I have been told since emailing you many of the same things. All these things are definitely key in my future filming. I was told by another about the ground glass being specifically important as well. Although I new about the ground glass, for my previous shoot I set the diopter based on opening up the f-stop and setting the focus to infinite and then adjusting diopter so that the buildings a couple hundred feet away were as sharp as possible, focusing on the lines and edges of the building. I’m not sure if the grain was as focused as possible because I hadn’t learned that information yet and didn’t think to check. Although my future focusing will definitely involve the grain on the ground glass, is the method I used incorrect? I have to send all my rolls in at once due to budget constraints so theres no way to see if I should reshoot or not. Budgeting also is an issue for reshooting with this new knowledge. Everything was focused to my eye and then rechecked by my DP. Should I be worried or am I being overly concerned? I have never shot on 16 and want my first project to be a success in my academic journey into 16. Again thank you for the detailed response and it is very appreciated.
Dear A. B.,
I just found your reply in my junk e-mail folder. Entourage, my main e-mail software, can be a pain at times. Most sorry I did not spot this e-mail earlier.
Your method of placing the lens to infinity and opening up the iris all the way impresses me that you seem to understand the principal of an open iris will diminish the the area of acceptable focus. Your next procedure of using infinity lens focus as a “trick” to make sure the lens is in calibration, is correct but might be premature. (By the way, opening up the iris all the way has ruined many a student project. Make darn sure you reset the iris to proper setting before filming.) The process you followed worries me a bit. The eye focus adjustment (diopter) must be properly set so the grain you see in the viewfinder achieves best focus before you do anything with the camera. I tell students to shoot a blank wall or even a sheet of paper so they and YOU are forced to concentrate on the viewfinder screen grain.
AFTER you can guarantee that the ground glass is in proper focus, THEN shoot objects at infinity with the lens and shoot building edges and power lines to see if the lens is in proper calibration.
What you can do if you find a perfect lenses: You can do the Siemens star chart tests for closer than infinity to make sure that the lens is accurate all along its markings. If you know for sure that the lens is dead on perfect for focus at every mark on the focus ring, you can then run a “TAPE” (tape measure) out from the camera to the subject and then rotate the lens focus ring to the corresponding mark. Every professional camera has a film plane marking. It looks like a circle with a line through it and the line is ALWAYS vertical. I personally would viewfinder focus the shot and then tape it to check that my eye had found the correct lens focus plane. The reason for this is my eyes are getting a bit old and that ground glass just does not do it for me every time. In other words you can viewfinder the camera for correct focus. You can actually tape the camera for correct focus (only if the lens is perfect for the camera you are using). Best of all, use both methods and you should NEVER get back out of focus film.
Tip: Proper focus requires LINES. I defy you to find proper focus shooting a black curtain with no wrinkles. I love shooting women with all that eye make up that approaches a Siemens start chart. LOL. Always look for lines at the plane (from the camera) that you want to look the best.
Tip: When shooting a person, focus on the eyes! If the camera person can not determine accurate focus, for any reason, put a Siemens star chart at the SAME distance as the object you intend to shoot to make the setting of perfect focus more easy.
Tip: Just as I told you to make sure that you reset your iris to the proper setting before pushing film, ALSO make sure that the camera person sets viewfinder focus for his or her eye before they start the camera. You would not believe the number of student films that were shot slightly out of focus because the director viewed the scene, adjusted the viewfinder and then the camera operator took over and did NOT reset the viewfinder focus.
Another tip: If you go to college in a large city, you just might have a good film equipment rental house that you can use. Check their prices for equipment rental. If you think the college cameras are a problem, consider renting out a camera. Now here is the trick. Get other students to do their projects the same WEEKEND as you do yours. This ONLY works if the rental house closes Saturday and Sunday. Often times the rental house will consider equipment rental ONE DAY if you take the stuff out Friday and bring it back Monday. If you find a rental house that does offer this, fine tune it a bit by asking how early Friday can you pick up the equipment and how late you can return it Monday. You then split the costs with the other student groups. If YOU pay for the rental and check out the equipment, I suggest that YOU attend every shoot, guard and protect that equipment, and return it back to the rental house because you are financially responsible for loss or damage. Consider paying for insurance to further protect yourself. That insurance is typically offered by the rental house.
You asked, “Should I be worried or am I being overly concerned? You told me you shot the footage; it is done. Get over it. If it comes back out of focus, you will have more deeply and painfully learned some pretty basic and very important technical processes that need to be understood when using a film camera.
By the way, what college do you go to?
Extra credit question 1: why should you NOT set your lens ring to infinity to get the greatest (most) area in the scene in acceptable focus?
Extra credit question 2: where should the focus ring be set if NOT at infinity?
I hope this helps.