back focus help

T

Take1Media

Active member
ok i think i figured out why im having focus problems- if im far away from my subject and zoomed in from a decent distance this is where i cant get it sharp? if im within 10 ft the image is easy to focus and image looks crisp on playback.

im gonna set up the star chart again but im thinking my distance was off last time. how far should i be in feet distance from the chart? when i did this last time i was about 15ft away hopefully i can get this resolved

any advice is appreciated
 
70ft NO NO NO!

7-12 feet or 3 metres is more like it, it is also better to do back focus on a HD monitor as it is easier to see the siemens star fringing.
 
Well, the norm recommends 10 ft / 3 mts...

Check the HPX300 operating instructions on page 90... "Adjusting the Lens Flange Focus/Back"

H.
 
You also MUST have the iris wide open, especially with a 1/3 " sensor otherwise you can error in this critical adjustment.
 
Backfocus correction is very difficult with this cam even if you use a HD monitor which I did. The smallest change of the ring (and I am talking about less than a half a milimeter) gives already a dramatical chance in how the test star looks going to the center. There should have been a fine control on the the backfocus correction.
 
Another stupid possibility (meaning "I've done it") is the macro isn't clicked into the off position. That has nothing to do with the back focus, but if you didn't have the focusing problem from the beginning, this could be the cause.
 
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