Welcome to our community

Be a part of something great, join today!

Log in
  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

RPP Oddities...

C

Cail Young

Well-known member
Joined
Jan 2, 2007
Messages
1,852
Reaction score
0
Points
0
Age
40
Location
Melbourne, Australia
Website
www.inspirationstudios.com.au
As Claude at Rubber Monkey alerted me, there is a white ring inside the 85mm RPP imperials (at least the ones we both have) - it looks a bit out of place inside a lens. Like an anodisation step was missed or something.

Also, our 50mm seems to have mismatching iris witness marks - i.e. the iris setting doesn't match on both sides of the lens. This could be a perspective trick with the fat witness mark, or it could be a genuine fault in manufacturing - I need to get them up somewhere stable and have a good look. Anyone else seen this?
 
Evin Grant said:
The iris marks on three of our lenses didn't quite match up from side to side.
Click to expand...

I've seen that on other lenses in the past (can't remember which ones...maybe Zeiss?) - I used to wonder which side of the lens was correct, generally went for the operator side rather than the dumb side.
 
I just noticed the same on my set. A couple days ago we were testing focus on the primes and noticed the witness mark was falling just behind the measured length; 4'6" fell just underneath toward 4'.

Now looking at the way both sides are not equal, seems it may line up for correct focus distance on the lens and measured distance from the subject but on the dummy side. Anyone else getting these results?
 
I'll also add that I took the set in to a rental house here in Chicago and through them up on a projector. The tech was very impressed with their quality and performance. They own sets of S4/i Cookes and Zeiss glass etc and are accustom to testing for quality.
 
Cooke S4s:

"Focus is checked for each increment of
critical focus.

Focus scales are then engraved according
to the computer data entered for each
lens.

Cooke /i lenses are checked by computer
with readouts of all information
and metadata that will be used during
production."

LINK (page 8)>>>

But that's not so sure for each of any Zeiss lenses.

Also each of any Angenieux zoom lenses are checked with all marks:

"1. The lens calibration room is long enough to measure and inscribe each
witness mark on the focus barrel, even from 4 to 120 feet on the Optimo
24 - 290. The lens projector rolls on a calibrated track, and optimum focus for
each distance is confirmed by a sensor that measures contrast. For extra long
lenses, the back wall of the room opens up for distances to 300 feet, since there
are two of these rooms back to back.

2. After the witness marks are scribed on the barrel, it is then sent for engraving
and finishing.

3. The mechanical components of the barrels are carefully checked."

LINK (page 7)>>>
 
Evin Grant said:
The iris marks on three of our lenses didn't quite match up from side to side.
Click to expand...

How much were they off? Just checked on mine and they matched up on all 5.
 
I noticed the same problem yesterday with my set (first time using it). Upon closer investigation, it turns out that it's a matter of what angle you look at in regards to the witness mark. The truly scary part is that looking from above vs from below can make a 2/3 STOP DIFFERENCE!!!!! The reason for this is that the witness mark itself is at least 1mm away from the barrel marks therefore inviting errors of perspective. Huge flaw.
 
Michael Lindsay said:
The letters go up to K on the UPs so I don't know if that means they have 11+?

Michael
Click to expand...


Ultra Primes have about 15 different focus scales, each one fitted to the lens it best matches up with and designated by a two letter marking on the barrel. This is usually not a problem as each lens is individually collimated to hit the focus marks. When shooting 3D however you DO need matching scales if your lens control system cannot compensate for the variation between the two.
 
Eric J. Johnston said:
When shooting 3D however you DO need matching scales if your lens control system cannot compensate for the variation between the two.
Click to expand...

Presumably the focal lengths are slightly different, that's why they need a different scale, so for 3D it would make sense for both lenses to be as close as possible identical. AFAIK collimation would only effect the infinity mark, the other marks should then fall into place.
 
You must log in or register to reply here.
Back
Top