The Samyang 14 mm / 2.8 IF ED MC Aspherical super wide angle lens seems to have a misalligned focus scale often.
I suppose it is the same with the OEM lenses Bower 14 mm f/2.8 Manual Focus Aspherical Super Wide Angle Lens, Walimex Pro 14 mm /2.8, Vivitar 14 mm f/2.8, Falcon 14 mm f/2.8 ED Asph IF, Bell and Howell FE 14 M-C 14mm f/2.8 IF ED MC Aspherical Super Wide Angle and Rokinon FE14M-C 14 mm F2.8 Ultra Wide Lens .
There are two different methods around for this task.
The older one I found first here in a polish languange forum Canon-board.info, described on page 17.
Thomas Berndt, a German reader of my Samyang 14 mm / 2.8 review tried this focus scale correction, and described it in German language. I suppose that correction alter the IF - internal focussing.
My method goes to the other parameter - the flange back distance.
One can not know, which is "the right one".
As my in April 2011 bought Samyang 14mm f/2.8 lens had a severe focus scale misalingment or false flange back distance / register/ flange back length I tried to correct this with a more direct way:
You have to determine how thick the washers are that you will need:
For that you have to focus on an "infinity" object. Which distance shows the distance scale?
All in millimeter!
Washer thickenss = ( 1 / ((1/14)-(1/distance_scale_at_infinity))) - 14 (need to recalculate this)
I have a infinity object sharp in viewfinder and on the image (liveview) - and the distance scale shows 0.8 meter distance.
Washer thickness = (1 / ( (1/14)-(1/800) ) ) - 14 = 0.249 mm
Washer holes 2 mm diameter
Best is to search at first some washers with this thickness - better a bit to thin! To thick is bad!
And they need to have the exact (!) same thickness! Or you have a tiltet lens - Scheimpflug effect.
Shake the lens - and remember the noise (no noise for Canon EF mount).
Now open the three (or four on newer lenses) screws, take the mount near by the lens - best with the orientation as it had on the lens.
Now place the washers with needed thickness onto the screw holes of the lens.
Place the mount careful back to the lens - the screw holes have to fit directly.
Screw the screws in.
Shake the lens - same noise as before? Otherwise the washers are probably not there were they are supposed to be.
I took the three screws out of the mount ring - in newer versions there seem to be four screws.
It is good, that Samyang decided to take now 4 screws, because the screws are screwed in plastic!
Plastic is not bad - but for a lens that heavy I would prefer more metal. And yes, I tried different methods to test if its plastics or metal:
- Look and fell
- Scratching the surface with a screwdriver - it is still black and the feeling is not like metal
- I measured the electrical resistance in a scratch - not only on a coated surface
Now I searched some metall washers or something I could use like washers with the appropriate thickness
This is the modification. Lay the washers between the mount and the lens barrel, and screw the screws through the washers holes - so the lens is together again.
Probably it is easier to work with another method to build it together:
You could fix the washers onto the mount back with screws inside, and fix it temporary with some pieces of tape. Then take that prepared back onto the lens, screw the screws only a bit, an take the tapes away before screwing it together full.
One could use thicker washers to extend the near field capability of the lens - llosing the infinity setting. After my first tests with the Samyang handholded in front of the camera mount, this seems to be very interessting with good quality. For that you have tu assure that the mount still holds good enough - or you need longer schrews with exactly the same diameter!
And probably you need something to make the lens back light-thight again - some foam material for example.
I took a bit deeper look insinde the lens. Here you could see the ring that transfers the iris opening:
Here you could see how to move the iris:
At least I would reccomend to check now and then if your Samyang lens is still more or less stable. My lens front start after some time of using to wobble a bit. This could be repaired with this three screws on the outer lens diameter. This could lend to a false focus scale setting too!
After that I didn´t need the washers anymore :-)
Here you could see some signs of usage - after about six months in my photobag. But I have to admit that I do not coddle my normal photo equipment, the lenses are on near another in my back with notingh in between.
Other lenses looks much better after years of my normal usage.
More about typical / common problems the Samyang lenses with references!