samyang 35mm F1.4 focus slop

beomagi · Joined: 14 May 2010 Posts: 46

I just purchased a 35mm F1.4 Rokinon/Samyang in EF mount. This is the manual focus version.

Trying it out I noticed that if I go slightly past focus and then have to go the other way, I have to go quite a bit farther than expected.

So starting at infinity, I turned the focus until I got a point in focus - 0.7m marking.

Went past it, then went back to 0.7 - not in focus. in fact it didn't seem to change at all. Kept racking until it's in focus again. 3m marking.

Doing more testing. It seems that if I focus quickly, and stop, something inside is still moving, but very slowly. If I turn the focus ring and wait, I can watch as a point gets into focus, then back out. I'm guessing there's elements here that are spring mounted but either the spring is weak, or the lubrication used is too thick and binding it?

Dejan · Joined: 05 Jan 2021 Posts: 142 Location: Belgrade, Serbia

I'd just sent it back if that's a possibility. I have one of these and the focusing ring works perfectly. I don't think that dealing with this lens would be as easy as with an old Helios 44-2. It's Samyang, their quality control was never the best; besides who knows what happened to that lens before you bought it.

LittleAlex · Posted: Fri Feb 23, 2024 1:52 am Post subject:

Optically that lens is heaven, but mechanically (as nearly all of that company lenses are) - it is the pure hell. If you would look inside of it, you will be simply horrified. It scarcely survives the intensive use, and is nearly impossible to repair.

After I discovered it, I decided to stay away from any lens of that company in the future.

However, you might be able to look there:

https://www.dpreview.com/forums/thread/3847323

https://www.youtube.com/watch?app=desktop&v=Gu3qQlMNPUk

Possibly, it might help you.

beomagi · Joined: 14 May 2010 Posts: 46

beomagi · Joined: 14 May 2010 Posts: 46

Dejan · Joined: 05 Jan 2021 Posts: 142 Location: Belgrade, Serbia

This 35mm is as sharp as 50mm, if not better. Actually, I've had luck with all of my Samyang lenses (good centering, no mechanical issues); but they haven't seen much use and abuse. The 35mm is my personal favourite, MF version of 85mm I didn't keep (but the bokeh is perfect), 24mm is great (but not as sharp wide open as 35mm), MF 14mm version has terrible distortion (but it's a great astro lens and sharpness is fine). 135mm F2 lens always had the best reputation of them all (there's also less sample variation for some reason, I haven't heard of a bad copy yet). Perhaps you'll have better luck with a different sample. Sometimes you can get these for cca 100 eur on European eBay auctions (not sure about the rest of the world), so just keep an eye open.

caspert79 · Joined: 31 Oct 2010 Posts: 2936 Location: The Netherlands

I used to have the 20/1.8 and 85/1.4 mk2. Mine were good, but they were impossible to sell again at a decent price. I guess that has to do with the so-so reputation of the build quality.

Alsatian2017 · Joined: 05 Mar 2018 Posts: 237

BrianSVP · Joined: 09 Jun 2023 Posts: 305 Location: Philadelphia

Cost cutting is certainly very common among the third party manufacturers as a way of providing optically superior products while undercutting the OEMs. For example, even as it's reputation has grown, Sigma has lenses in its high end ART line that are literally held together with tape, and they still reverse-engineer AF protocols in order to avoid licensing fees to OEMs.

I'm not as horrified by Samyang's construction as others in this thread. They are certainly better than some of the Chinese third party manufacturers, not to mention the various zombie European manufacturers like the so-called "Meyer" who until recently were making their barrels on hobby grade equipment.

As far as plastic bearings go, their use in and of itself is not a red flag. All but the very highest-end AF lenses use similar bearings, since a traditional greased helical would overload the AF motor. Manual lenses with internal floating elements use them, too, since a slot and bearing arrangement can provide a lot of gross and nonlinear front-to-back movement without adding excessive friction or unevenness to the focus action. Typically, they are not actually roller bearings but simply pressed-on bushings that rely on the natural lubricity of the nylon or delrin which they are made from to slide in their slots. They can last a very long time, provided they are made out of quality materials. I suspect the problems with Samyang stem from the use of inferior plastics in their bearings.

Very high end pro-grade lenses use true roller bearings made of steel, and are mounted on eccentric screws so they can be given precision adjustments, but on most lenses, the plastic bushing is on a simple symmetrical post, and when they wear unevenly or tear, that's when you start to see problems with image quality.

Incidentally, mounting screws sunk into plastic is also a common feature of everything but the highest-end AF lenses these days, even among OEMs. It's more a symptom of a quest for weight savings than necessarily a cost cutting measure.

RokkorDoctor · Expire: 2025-05-01

Just for information;

I saw slots and bearings mentioned a few times. In the (lens) engineering worlds this construction is called a cam mechanism, consisting of the cam-slot (the slot) and the cam-follower (the bearing/post).

Wear on the cam-follower is usually due to a poor surface finish on the cam-slot. In the good old days of precision-machined cam-slots and metal cam-followers there would be a grease with a dry-lube such as molybdenum-disulfide used in there which greatly helps reduce wear.

Nowadays the cam-follower often consists of a nylon/delrin bushing and low-cost lenses may not use much in the way of a good lubricant at all. Cam-slots that have been roughly machined in aluminium can wear down those nylon/delrin bushings on the cam-follower pretty fast. If the bushings are non-rotating ones held by a screw, then loosening the screw, rotating the bushing 90 degrees and re-tightening the screw may extend the bushing's working life a bit longer.