Distance scale estimating

[Jim Kuo]

I am looking for some instructions to help me better understand the distance scale available on some lenses.

e.g. Canon EF 35mm f2 Lens (2507A009AA) - wex photographic

The distance scale on this particular lens is very simplified and only shows F11 and F22. I understand that (please correct me if I am wrong), F8 lets in twice the light of F11, can I assume if Canon were to add a mark for F8 on this lens, the F8 mark should be at the middle of F11 mark and the center (I call it 0)? And again F5.6 should be at middle of F8 mark and 0?

Is this guess work roughly correct, or I am completely off the mark?

I understand that the distance scales on these lenses are not exact, and with such short focus rotation, and focal length, the actual focus distance probably wouldn't make too much difference to the perceived sharpness in pictures in practice (using small enough aperture). But I am hoping to receive some instructions to help me make better theoretical estimation based on data available to me.

Also, given the following distance scale example,

How do I read this? For example, where is the 2m mark? Is it exactly at the middle of 1 and 3?

Confused... Thanks.

Jim

 

[Hamish Gill]

Trying to use scales on modern lenses is pretty pointless if you ask me ... The focus throw is far to short!
Older lenses make it easier http://www.realphotographersforum.com/content/281-how-zone-scale-focus.html
In answer to your question, 2m would be closer to 3m...

 

[Jim Kuo]

Thanks Hamish. I tried very hard to make sense of the modern scales and have come to the same conclusion...

Also thanks about confirming the position of the 2m marker.

 

[Hamish Gill]

No probs ...
A very useful thing we have lost on modern lenses if you ask me ...
One of the reasons I like the scale in the vf on the x100

 

[Austin O'Hara]

... The focus throw is far to short!

Does the above quote mean that a small angular rotation of the focus ring produces a large change in focus?
So an ideal lens would have a small change in focus for a large angular rotation?
I am trying to update my knowledge concerning "photo language".
Thanks in advance.

 

[Hamish Gill]

yes
and thats ideal lens for manual focus in my opinion

 

[Pete Askew]

I agree and the older Nikon 135's have a very fine focus thread on them.

The only lenses I have that need more rotations are the Zeiss Compact Primes - but these are video / cinema lenses!

 

[Hamish Gill]

I've been meaning to ask Pete ...
I was going to start a thread but it's really just passing interest ... Is a follow focus easy to use?
At some point I was thinking of buying a Sony NEX and making my self a little camcorder rig ... Bit skint at the mo ... But it's been a plan for a while

 

[Pete Askew]

Sorry, missed this before. Yes, a follow focus is easy to use even on a non-cinema lens. However, it's worth thinking about rotation when you come to buy, especially if you intend to use lenses from different manufacturers. I've standarised on LH focus control (most do) and forward rotation (ie anticlockwise) takes you towards infinity. So for Nikon lenses I need a different FF unit to Zeiss as they focus in different directions. You can get some on which you can swap the side of the gears and that allows you to keep the same rotation. I found it easier to have two units (they snap on and off the rails). I'm using Genus units (the Superior FF on the CPs).

Genus Video and DSLR products - Genus Video and DSLR products - Genus Video and DSLR products

http://www.realphotographersforum.com/digital-camera-video/4984-zeiss-compact-primes.html

A very helpful place to buy from is Production Gear at Elstree. Simon is always very good with his advice.

Production Gear Ltd

 

[Hamish Gill]

Cheers Pete
there is one called the RJ follow focus .. Cheap as chips but supposed to be extremely good or the
money ...
Anyway it's all just day dreaming for now ... I don't even have a camera with good video yet!