Graham Murphy Posted April 7, 2007 Share Posted April 7, 2007 Hi All, I was wondering if anyone could tell me what the proper procedure is in which to perform a "harp test" for lenses? I've looked up the archives and couldn't really find much. Thanks in advance. Cheers, Graham Link to comment Share on other sites More sharing options...
Nick Mulder Posted April 7, 2007 Share Posted April 7, 2007 Source yourself some chewable morphine (the cherry flavor gummy-bear version in my opinion is the most effective :wub:) ... then pretty much follow the instructions here Just like time-lapse really... Link to comment Share on other sites More sharing options...
Mike Panczenko Posted April 8, 2007 Share Posted April 8, 2007 What is a harp test- I can't find much on google. Link to comment Share on other sites More sharing options...
Premium Member Chris Keth Posted April 9, 2007 Premium Member Share Posted April 9, 2007 What is a harp test- I can't find much on google. I have never done it but read some stuff about it. I get the idea that it's a more elaborate version of shooting a ruler at various stops to have a good visual sense of your depth of field. It involves something in the realm of a bunch of resolution targets at difference distances shot at different f/stops. Link to comment Share on other sites More sharing options...
David Negrin Posted August 18, 2007 Share Posted August 18, 2007 Hi All, I was wondering if anyone could tell me what the proper procedure is in which to perform a "harp test" for lenses? I've looked up the archives and couldn't really find much. Thanks in advance. Cheers, Graham I've never heard it called a harp test before, but, a card test yes. Take a 1x3 board 24'' long, cut slices every inch not going all the way through the board. Grab the board with a c-stand and set it horizontally, Place your rig with the center slot @ 5' to the film/ chip plane. Put the ace in the center slot ( hold cards in place with tape shims) Place red or black cards going away from camera and the opposite color coming towards camera. fan them out so all you see is the # and suit in the corner. find out at what stop your lenses were calibrated, most camera houses go at t-2.8 . When you see the set up you will see how the focus falls off on the lens, The numbers going back from the ace might be soft @ the 3, while the cards coming towards the lens might fall off @ the 2. giving you the results on the focus carrying 2/3rds back, and then you can play your depth ( if you need to) more effectively. I have to admit I haven't heard of anyone doing one in over 10 years. Link to comment Share on other sites More sharing options...
christian hennermann Posted August 23, 2007 Share Posted August 23, 2007 I've never heard it called a harp test before, but, a card test yes.Take a 1x3 board 24'' long, cut slices every inch not going all the way through the board. Grab the board with a c-stand and set it horizontally, Place your rig with the center slot @ 5' to the film/ chip plane. Put the ace in the center slot ( hold cards in place with tape shims) Place red or black cards going away from camera and the opposite color coming towards camera. fan them out so all you see is the # and suit in the corner. find out at what stop your lenses were calibrated, most camera houses go at t-2.8 . When you see the set up you will see how the focus falls off on the lens, The numbers going back from the ace might be soft @ the 3, while the cards coming towards the lens might fall off @ the 2. giving you the results on the focus carrying 2/3rds back, and then you can play your depth ( if you need to) more effectively. I have to admit I haven't heard of anyone doing one in over 10 years. oh, yes, they do it in cape town my bru! it's part of every propper camera/lesns test. even though i must admit it's realy a bit too much. the meaning of the harp test is to make sure that ur eyefocus is correct. calibrating the eyepiece is nbot enough. u perform a lens test in order to make sure the focal length from the lens/camera mount to the film gate is correct. the harp test makes sure the focal length from the camera mount to the eyepiece is fine aswell. it should be 52mm(for ARRI) just like the focal length of the filgate. if it is incorrect u'll get into toubles when u rely on eyefocus instead on ur measuretape. we taek a test chart that consist of thin lines (about one every 1cm). if u twist it it looks like a harp. place it in front of the camera, close focus, take a long lens e.g. 85mm, open the stop to create a small depth of field. now focus one of the lines and mark it with a arrow or colored dot or whatever. the lines running away from the camera and the closer ones should be slighty out of focus and completly soft. shoot it and looking at the test the result needs to look just like what u've seen through the eyepiece. if not- if any other line is more in focus than the one u've marked withe the arrow/dot- u need to fix the focal length from camera mount to eyepiece. but i've honestly nerver heared of anyone who had to adjust it.... cheers Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now