Rokinon/Samyang 14 F/2.8 focusing help!

Hi all - I'm looking for some assistance in learning to use this lens better (or maybe just learn to use it - PERIOD.) Sorry in advance if this isn't the right place for this thread. I didn't think it belonged in the sample images thread, so this was the next logical place (in my mind).

This is my first completely manual focus lens (mine is a Rokinon) and in the limited time I've had it and tried to use it, I haven't quite caught on. I'm having problems telling, when using the view finder and even LV, when my focus is sharpest. The family and I will be heading out to Arizona this next week and I think this will probably be my best bet to REALLY get to use this lens. So I'm trying to do a little more homework before I'm actually out in the desert

I have an idea for trying to use this lens more efficiently, that I want to run by anyone willing to read/comment... I've read about people who have printed out, or stuck hyperfocal distances for certain apertures to the cap or lens, and I've read some people who say to set the lens to f/2.8 and focus at infinity... but are they just getting the focus "close enough"? I don't know if "close enough" is good enough for astro, for example.

What about picking a few apertures, say 2.8, 5.6 and 11 and then setting up a target (something like you'd use to MFA a camera/lens) and then put the camera on a tripod at each hyperfocal distance and then 10x LV to find the best focus. Then take some white duct tape (or something similar), cut into a thin strip and marked some way and stick these to the focus ring.

For example, for f/2.8, I'd get myself back ~7.62 feet from the target and find the best focus. Then take the small strip of tape and maybe mark it with a single black line. Next, set lens at f/5.6 and refocus from ~3.84 feet - mark this spot on the focus ring with thin piece of tape and two black lines... etc. etc...

What do you think? Do I just need more time with the lens (duh) or will something like this trick or another work for a newbie like me?

Thanks for your time!

I did something similar with my lens, but only for hyperfocal.

I find focused to get the corner as sharp as possible @2.8 with the backyard fence (shot from inside the house).

once I find the spot, I cut a tiny strip of gaffers tape and put it on the focus lined up with the focus pointer. F11 tends to give me the best result, so I put a tiny piece of gaffers on the 11 as well. Of course if shooting something really close, then may need to focus stack, one shot foreground, one shot background with preset settings.

btw, focus wide open, then stop down, no need to mfa with this lens and no need to test focus stopped down.

I bought this lens for its HUGE DOF. Just play with it. I've gotten to the point where I don't bother to focus. My starting point is focusing at 5' and using f/8. Everything from 2' to infinity will be in focus. If you need more aperture, f/5.6 is about the same. You can focus at 3' and f/8 and still have everything from 18" to infinity in focus. If you need CLOSE FOCUS (less than 2') AND F/2.8, use 10X LV. Spend an hour NOT focusing this lens. You'll be amazed at the results.

My Rok 14 has slack in the focus. I get a different sharpest focus position depending on which way I'm rotating the barrel. Make sure you turn 'past' the point of best focus by enough degrees so you don't encounter the slop.

Hey guys, thanks for the replies, appreciate it!

Charlie wrote in post #17427358
I did something similar with my lens, but only for hyperfocal.

I find focused to get the corner as sharp as possible @2.8 with the backyard fence (shot from inside the house).

once I find the spot, I cut a tiny strip of gaffers tape and put it on the focus lined up with the focus pointer. F11 tends to give me the best result, so I put a tiny piece of gaffers on the 11 as well. Of course if shooting something really close, then may need to focus stack, one shot foreground, one shot background with preset settings.

btw, focus wide open, then stop down, no need to mfa with this lens and no need to test focus stopped down.

So you are basically only doing the testing/labeling to figure out where you are sharpest to the corners at F/2.8? So you'd agree that it isn't necessarily going to be just spinning focus to infinity?

GeoKras1989 wrote in post #17427395
I bought this lens for its HUGE DOF. Just play with it. I've gotten to the point where I don't bother to focus. My starting point is focusing at 5' and using f/8. Everything from 2' to infinity will be in focus. If you need more aperture, f/5.6 is about the same. You can focus at 3' and f/8 and still have everything from 18" to infinity in focus. If you need CLOSE FOCUS (less than 2') AND F/2.8, use 10X LV. Spend an hour NOT focusing this lens. You'll be amazed at the results.

When you say you start focusing at 5' and f/8 do you mean setting the focus ring to 5' or do you mean you are 5' from your subject? I'm assuming you mean you are 5' from the subject, so then is your focus ring at infinity? And assuming you are at infinity, you are saying the focus is acceptably sharp? Again, I haven't really tested mine, but I had read about people saying they couldn't just sent to infinity because it was actually sharper elsewhere on the dial.

skid00skid00 wrote in post #17427474
My Rok 14 has slack in the focus. I get a different sharpest focus position depending on which way I'm rotating the barrel. Make sure you turn 'past' the point of best focus by enough degrees so you don't encounter the slop.

Interesting. I haven't noticed any slack in focus, but I haven't used mine too much. It's basically brand new. My question was really more about how to find best focus, but now you are telling me that I have to potentially worry about turning past what I cannot find, I'm screwed!?!?! haha

freestylee30 wrote in post #17427528
When you say you start focusing at 5' and f/8 do you mean setting the focus ring to 5' or do you mean you are 5' from your subject? I'm assuming you mean you are 5' from the subject, so then is your focus ring at infinity? And assuming you are at infinity, you are saying the focus is acceptably sharp? Again, I haven't really tested mine, but I had read about people saying they couldn't just sent to infinity because it was actually sharper elsewhere on the dial.

What I meant was:
Set aperture to f/8 (f/5.6 is close enough).
Set the lens focus at 5'. No need to focus on a subject.
Everything from 2' to infinity will be in focus.

There is no need to refocus UNLESS you:
1.) Want to use a wider aperture on a close subject.
2.) Want to use f/2.8 on any subject.

I walked around the campus of Indiana University for over an hour, taking perhaps 40 shots. I got wide 'campus-green' landscapes and close-ups (2'-3') of plants and fire hydrants. The lens was set to f/8 and focus was set at the 5' mark on the lens. I NEVER TOUCHED FOCUS OR APERTURE FOR THE ENTIRE HOUR. Everything was in focus. I had some composition garbage, but no OOF shots.

And that is my point. For the most part, this lens does not need to be focused. Set it. Forget it. Shoot it.

EDIT:
I started this hobby with cameras that had no focus mechanism. In the 1970s I moved to SLR which, at that time, had no auto focus ability. In about 2009, I bought my first digital SLR. Auto focus is simply amazing, most of the time. It is not required, or even necessary. You can get by with out it, quite easily.

Ok, thanks GeoKras, appreciate you spelling that out for me!

I think what confused me is that I can't look at my lens right now and I was pretty sure it only had specific marks for feet, ie: from like 1' to 3' to 7' then 10' and infiinity or something like that, so I guess I assumed you meant 5' from subject.

Anyways, if I don't have a 5' on the barrel then presumably between 3' and 7' would be the spot to try out. I'm going to have to spend some more time with it, obviously.

Yep, I guess at 5', too. This is a fun lens to shoot, once you get over the focus 'obsession'. Besides, its digital. If the shot is OOF, take it again.

Hey there -

Thought of another question, not related to focusing, but I was curious to know what you guys are having the best luck with for lens corrections. I have the "5dii + Samyang 14mm RAW" profile loaded into Lightroom. Appears to do a decent job, but I haven't used it much so I'm not sure. Anyone use PTLens and think it does a better job?

Thanks again!

I've posted a few shots that I corrected for distortion with that LR profile. Commenters stated that PTLens does a better job with distortion. Vignetting corrections necessarily have to be manual; the camera does not know what aperture you shot at.

I only use PTLens "mustache" correction when it looks very obvious in the photo.

PTLens auto correction http://epaperpress.com​/ptlens/

Straight from camera

Thanks guys - looks like I will have to try PTLens and compare.

msowsun - thanks for the examples. Good idea with the brick wall test. I've seen that for checking sharpness but I hadn't thought about using it to test lens corrections. Also the GIF is good, helps my untrained eye better see the distortion.

DOF on a wide angle lens is huge. As others have pointed out if you know a few things about how to set up the lens you should be fine. Roll on over to http://www.dofmaster.c​om/dofjs.html and plug in some numbers, noting all of the calculated figures. Once you've played with that, like other's have said, just get out and shoot a little. The margin of error is great, if you are seeing softness you might want to start looking at a problem with the lens. If I recall, this one has a lot of decentering issues.

Mike,

I like the distortion correction. Is PTLens doing auto-vignetting, too? Seems that has to be manual, and different for every aperture.

Left Handed Brisket wrote in post #17428524
DOF on a wide angle lens is huge. As others have pointed out if you know a few things about how to set up the lens you should be fine. Roll on over to http://www.dofmaster.c​om/dofjs.html and plug in some numbers, noting all of the calculated figures. Once you've played with that, like other's have said, just get out and shoot a little. The margin of error is great, if you are seeing softness you might want to start looking at a problem with the lens. If I recall, this one has a lot of decentering issues.

Hi LHB - I've looked at this site and messed around with it before, but thank you for reminding me, because after having these conversations it helps to reinforce the discussion. I see the correlation between apertures and acceptable sharpness, the more stopped down, the larger the DoF, however the part I was having issue with is the focus ring.

Specifically that when I was first trying to use this lens, I was using it at f/2.8 because I was indoors and it is very difficult for me to determine where on the focus ring the view was the sharpest. In certain situations I could point the camera at something obvious (words on a box or something) and achieve decent focus, but even that wasn't easy or natural for me. Forget trying to get a shot of my 2 y/o while he's coming in closer and running away from me... I have pretty good eye sight and don't feel the same struggle in trying to manually focus my 50mm, etc.. I'm guessing it is because of the huge field of view of the 14mm, compared to something like the 50?

I went out a little yesterday afternoon with the lens set at f/5.6 and f/8 with the focus ring at ~5' and like GeoKras said, it was pretty darn good. Maybe I could tweak to find better, but it was acceptable.

I guess what I am struggling to get the hang of, is why 5'? Why not 3' or 7' on the focus ring? What about when I'm using f/2.8 or f/16, 5' probably isn't going to be as accurate then, but how do I know what's accurate without doing some testing and marking of the lens. I'm guessing there is some theory or formula that I'm missing, but for now I'm pretty content for now knowing I can set it to f/5.6 - f/8 and 5' on the focus ring and get some good shots, but still trying to figure this part out.