Schneider-Kreuznach RX lenses auto depth of field

[alexandros petin]

Hello,

i was using my bolex REX 4 mainly with the 18-86 OE zoom. Now i want to use my schneider primes and i noticed that not all of my lenses have the auto depth of field with 3 colors red-yellow-green.

As you can see in the photo only red, no green and/or yellow. I looked online for images of the RX lens set and each has this feature, so unless there was a version sold with only red markings, something's wrong with these lenses.

Any ideas?

 

Edited May 3, 2025 by alexandros petin

[alexandros petin]

For future reference and for others having the same issue. To my understanding, without dismantling the lens, it seems that when i open/close the diaphragm of the lens with all colors, colored lamelas slide up and down along the lens length to color the Dof indication opening according to the DoF. The lenses with only red color have the same mechanism principle but in place of green and yellow only silver parts slide. This makes me think that either somehow the green and yellow colors faded, or the silver parts should "catch" hidden colored ones and make them slide into place, but they are not.

Anyway these are scheduled for service, but wanted to know beforehand what is wrong, if they can be fixed. I will update this topic once i know more.

[alexandros petin]

On a side note and off topic, i joined this forum back in 2007 and was enjoying it more regularly until 2011. Then i had occasional visits, until this recent post of mine, since when i refreshed reading through posts some things film related, caught up with nice topics that i had missed etc.

A lot has changed since 2011, but as i am member of relevant facebook groups too, i wonder if facebook has "killed" the forums. In facebook posts receive lots of answers and reactions, similar to how i remember this forum.

Problem is forums compared to facebook are designed to cultivate discussion, store information and knowledge in an organized fashion with subforums, while facebook imo promotes immediacy of interaction regardless the topic at hand, but the information is not in anyway classified [besides the group, albeit too general, name, for example Super 8mm] and/or retrieved easily.

[alexandros petin]

Back with another observation i totally missed.

As shown in the image of the first post, the lenses that have only red indication do not have the green T True Stop markings etched on the barrel like the one in this post.

After realizing this, a quick google search confirms that lenses with T values etched on the barrel have the red yellow green Dof indication, while the ones without Ts only red.

In conclusion, it seems there is nothing wrong with the lenses, but there are at least two versions of Schneider RX lenses with T values and tri-color Dof indication as main differences.

 

[Don H Marks]

How does one read the DOF scale? Like, what does the yellow and green stand for? Different zoom settings?

[alexandros petin]

Hello Don,

for the RX primes set according to this document page 12 

"Two automatic depth-of-field scales meet either normal or critical requirements. "

so green area is critical, yellow normal and red out of acceptable focus.

The above document, as stated in pacificrimcamera.com, is undated but probably from the late 60s (1968).

 

The 1955 document does not mention any DoF indicator, and also there is one image with silver schneider lenses only.

 

The 1963 document is more specific in page Sixteen

"Two ranges of depth are provided : Red field for normal use and a yellow field for most exacting demands (circle of confusion of 1/1OOOth. of the diagonal.)"

 

All these make me think that lenses with only red indicator are late 50s-early 60s versions, that got not long after updated with T marks and normal-critical requirement DoF indicators.