[Laurentiu Cristofor]

The length is what matters and that is a result of both diameter and angle of rotation. But because differences in lens diameter are not usually that large to matter, people will just compare the focusing in terms of angle of rotation and that will work great for most comparisons - for most, but not all.

Using angle of rotation alone is not enough when comparing an 85/1.4 lens, which is large, with slower 85s, which will be considerably smaller. The size difference between an 85/1.4 and an 85/2/1.8 is quite significant. For such comparisons, the diameter of the focusing ring does matter. Even a 90 degrees turn may work fine with a really wide lens. The Vivitar Series 1 35-85/2.8 has such a 90 degrees turn, but because it is very wide, that turn is sufficient for precision focusing and feels very nice to use.

FWIW, the Zeiss 85/1.4 has both a large diameter and a ~260 degrees turn. It is very satisfying to focus on static subjects but it is very challenging to adjust focus fast for moving ones. I used the Samyang a bit and I found its focusing to be very precise - I don't even remember the throw - you don't pay attention to that when it works well.

[Laurentiu Cristofor]

But this lens can't be stopped down, at least not like a preset lens can. This lens behaves like an M lens; diaphragm stays wide open, closes momentarily when the shutter release is fully depressed or when the green button is pressed to meter. Regardless of the lens' aperture setting, lens is wide open while focusing. I thought the minuscule dof might make focusing difficult but in the short time I've had this lens (one week), focusing was surprisingly easy and accurate. It might be a different story if and when I shoot portraits with this lens.

Stopping down isn't supposed to help you nail the focus in the viewfinder - it's just supposed to make mistakes less costly because the DOF is larger and thus you have a higher chance of getting in focus whatever it is that you wanted in focus.

Stopping down on preset lenses is actually challenging because the viewfinder will be darker and then it's harder to appreciate focus. That is why I prefer preset lenses that allow me to focus wide open and then let me flick a ring to stop down just before I take the shot - lenses like the early Helios-44 versions, for example.

[excanonfd]

Stopping down isn't supposed to help you nail the focus in the viewfinder - it's just supposed to make mistakes less costly because the DOF is larger and thus you have a higher chance of getting in focus whatever it is that you wanted in focus.

Sure it does, I used to do it all the time when I shot with a Canon T90 and 50/1.4. I would push and lock the DOF preview slider to darken the viewfinder to fine tune the focus. Of course, there is a limit to doing this - when the split prism starts to black out too much but using micro prism or the matte portion of the viewfinder to focus, one can get quite accurate focusing down to f8 or so.

Stopping down on preset lenses is actually challenging because the viewfinder will be darker and then it's harder to appreciate focus. That is why I prefer preset lenses that allow me to focus wide open and then let me flick a ring to stop down just before I take the shot - lenses like the early Helios-44 versions, for example.

But an A type lens like the Rokinon 85/1.4 is doing exactly what you describe - automatically. When the viewfinder is too dark because of a slow lens and/or long extensions, accurate focus can be difficult to achieve. The same could be said when the viewfinder is too bright (fast lenses), due to the apparent depth of field that is far greater than the actual DOF. I had hoped the green button would stop down the lens and hold it stopped down until released, instead of only momentarily stopping down to meter.

Thanks,

[Laurentiu Cristofor]

Sure it does, I used to do it all the time when I shot with a Canon T90 and 50/1.4.

I cannot comment on what works for you; I was just explaining what I meant when I mentioned focusing at smaller apertures. FWIW, I don't find optical DOF preview helpful for anything - on digital, I can just take a shot and see the result - which is why the camera control is set for the digital capture as default mode of operation.

But an A type lens like the Rokinon 85/1.4 is doing exactly what you describe - automatically.

Yes, but the paragraph you responded to was specifically about the experience of using *preset* lenses - it doesn't apply to the Rokinon.

[Byrd-2020]

I tend to agree with excanonfd here. It could be that the focusing problems described earlier are due to focus shift rather than shallow dof and mechanical aspects of the lens (or poor eyesight). As I understand it, many high speed lenses exhibit this phenomenon--including my Zeiss 85mm f1.4 zk.

Uncorrected spherical abberation will typically (though not always) push the actual plane of focus further away as the lens is stopped down. (At some point increasing depth of field hides this.)

This is why I always focus stopped down on my Zeiss 85mm when shooting at f2 or f2.8. (Sometimes at f4 as well.) The problem though, as mentioned above, is that this becomes impractical as the viewfinder darkens. Still, a failure to do this--at least when close focusing--has often resulted in misfocused images.

[excanonfd]

Yes, but the paragraph you responded to was specifically about the experience of using *preset* lenses - it doesn't apply to the Rokinon.

Perhaps I misunderstood; you have more 85/1.4 lenses other than the Rokinon, including an 85/1.4 that can be manually stopped down? Man, your LBA is much worse than mine!

Thanks,

[excanonfd]

I tend to agree with excanonfd here. It could be that the focusing problems described earlier are due to focus shift rather than shallow dof and mechanical aspects of the lens (or poor eyesight). As I understand it, many high speed lenses exhibit this phenomenon--including my Zeiss 85mm f1.4 zk.

Uncorrected spherical abberation will typically (though not always) push the actual plane of focus further away as the lens is stopped down. (At some point increasing depth of field hides this.)

This is why I always focus stopped down on my Zeiss 85mm when shooting at f2 or f2.8. (Sometimes at f4 as well.) The problem though, as mentioned above, is that this becomes impractical as the viewfinder darkens. Still, a failure to do this--at least when close focusing--has often resulted in misfocused images.

Wow, that's interesting. Prior to acquiring the Rokinon 85/1.4, I did not have any truly fast lenses other than the fast 50's, and most of the time they were shot at the optimum diaphragm opening of between f5.6 and f11.0. The Rokinon has an aspheric element to correct the spherical aberration but the 50's do not. I wonder how a Pentax A 50/1.7 which cannot be stopped down to focus would fare against a 50 that can be stopped down. Another interesting experiment to try.

Thanks,

[Laurentiu Cristofor]

Perhaps I misunderstood; you have more 85/1.4 lenses other than the Rokinon, including an 85/1.4 that can be manually stopped down? Man, your LBA is much worse than mine!

Let me clarify: Once upon a time I just said I find 85s harder to focus than 50s@1.4. Even when they are slower or stopped down (f/2, f/2.8). You then mentioned preset lenses and I just made a generic statement about focusing with preset lenses - not about preset 85/1.4 lenses (never had one).

This is why I always focus stopped down on my Zeiss 85mm when shooting at f2 or f2.8. (Sometimes at f4 as well.) The problem though, as mentioned above, is that this becomes impractical as the viewfinder darkens. Still, a failure to do this--at least when close focusing--has often resulted in misfocused images.

The viewfinder shouldn't darken with the Zeiss because it is an A lens. What camera are you using it on?

[excanonfd]

For some reason, I find 85/1.4 lenses hard to focus, no matter the throw. I can focus fast 50s all right, but for some reason I always have more trouble with 85s, even when stopped down.

This is your original post in the thread to which I've replied to. You wrote "85/1.4 lenses", and "more trouble with 85s", which seemed to imply that you have handled more than one 85/1.4 lens. And then there is this; "even when stopped down", which I took to mean that you have handled an 85/1.4 lens whose maximum aperture can be reduced, ie: stopped down. In the context of focusing, "even when stopped down" is meaningless since focusing is done with the lens at wide open for any A type lens with Pentax DSLR. You seem to be confusing stopping down to obtain the correct exposure with stopping the lens down to focus, two completely unrelated issues.

Thanks,

[Rondec]

This is your original post in the thread to which I've replied to. You wrote "85/1.4 lenses", and "more trouble with 85s", which seemed to imply that you have handled more than one 85/1.4 lens. And then there is this; "even when stopped down", which I took to mean that you have handled an 85/1.4 lens whose maximum aperture can be reduced, ie: stopped down. In the context of focusing, "even when stopped down" is meaningless since focusing is done with the lens at wide open for any A type lens with Pentax DSLR. You seem to be confusing stopping down to obtain the correct exposure with stopping the lens down to focus, two completely unrelated issues.

Thanks,

I thought that lenses didn't stop down to focus, unless you manually set the aperture ring to a different setting. If you are in 'A' mode focusing is done wide open and the camera only stops down during the shot. Maybe I am wrong though...

[Byrd-2020]

Laurentiu Cristofor writes: "The viewfinder shouldn't darken with the Zeiss because it is an A lens. What camera are you using it on?"


Of course, it darkens. I have the lens set on A, and then I pull the stop down ring surrounding the shutter release to the right. At least this is how it works on my K-7.

You have to make sure, though, that you are set for 'optical preview' rather than 'digital preview' in the menus. (See pp. 130-1 in the K-7 manual.) My Pentax FA and Voigtlander lenses work the same way.

[Laurentiu Cristofor]

This is your original post in the thread to which I've replied to. You wrote "85/1.4 lenses", and "more trouble with 85s", which seemed to imply that you have handled more than one 85/1.4 lens.

Yes, I used a couple of 85/1.4s and a couple of 85/2. That part is correct.

My point was that I found it harder to focus these lenses at 1.4, 2, even 2.8. f/2 was actually the maximum aperture of some of these lenses, so focus shift couldn't be a factor in those instances.

And then there is this; "even when stopped down", which I took to mean that you have handled an 85/1.4 lens whose maximum aperture can be reduced, ie: stopped down.

Yes, that is correct. Also, 85/2 lenses can be said to be stopped down even when used at maximum aperture, in comparison to an 85/1.4 lens.

In the context of focusing, "even when stopped down" is meaningless since focusing is done with the lens at wide open for any A type lens with Pentax DSLR. You seem to be confusing stopping down to obtain the correct exposure with stopping the lens down to focus, two completely unrelated issues.

I was neither referring to exposure nor strictly to focusing. I was just talking about increased DOF obtained when you use a smaller aperture. As you should be aware, focusing errors have less impact when DOF is thicker. That is all I was talking about.

I thought that lenses didn't stop down to focus, unless you manually set the aperture ring to a different setting. If you are in 'A' mode focusing is done wide open and the camera only stops down during the shot. Maybe I am wrong though...

On second thought, he might be using the optical DOF preview control to focus with the lens stopped down and avoid the focus shift.

[Laurentiu Cristofor]

Of course, it darkens. I have the lens set on A, and then I pull the stop down ring surrounding the shutter release to the right. At least this is how it works on my K-7.

Got it now. I thought you meant that the lens acted as a preset lens and the viewfinder darkened as a result of selecting a smaller aperture.

[victorshoup]

I'd like to comment on the focus throw.

Let's try to make an "apples to apples" comparison. The closest Pentax comparable to the Samyang is the A*85mm f1.4. The A*85/1.4 is the most modern manual focus 85/1.4 Pentax lens with an "A" setting, which is just like the Samyang/VS1. The focus throws are pretty similar on both these lenses, so neither one is better than the other's. They're both pretty much even (the Pentax's is a touch longer and that info is in my original report, but I don't think it matters much in everyday usage).

If you want to make an "apples to oranges" comparison, like comparing the Samyang/VS1 to something like the SMC Takumar 85mm f1.9, it's still not really clear if older glass has the advantage.

The Samyang has a larger diameter for a 1/3 turn focus throw. The Tak has a smaller body diameter but it has a 3/4 turn focus throw.

So here's the interesting part. When you measure off the actual distance of the focus throws, the Samyang's is approximately 9 cm versus the Tak's at about 7.5 to 8 cm. In other words the Samyang actually has a slightly longer focus throw. The Tak "feels" like it has a longer throw but that's actually an illusion because of the smaller diameter body.

Furthermore the Tak doesn't have the "A" setting which is an inconvenience (+1 Samyang).

I've got both the Samyang 85/1.4 and the SMC Takumar 85/1.9 in front of me right now along with a measuring tape.

And then there will be those that will just complain about long focus throws because it makes accurate focusing more slow.




Ah, you are experiencing the effect of focal length and shallow depth of field. Remember, the longer the focal length at a given f-stop, the shallower the DoF and therefore the harder it is to focus. There is a difference between a 50/1.4 and a 85/1.4. If you haven't done so suggest you get one of those Katz-eye focusing thingies, it will really help nail the focus.


So does anyone know what the fuss is all about regarding the SMC Takumar 85mm f1.9 and f1.8 lenses? I just got the SMC Tak 85/1.9 recently to see for myself, haven't taken any pics with it yet. And why doesn't the SMC Takumar 135mm f2.5 have the same reputation? If I apply the same logic it should be as well loved as the A*135mm f1.8, no?

Not to beat a dead horse, but..I recently got the Super Takumar 85/1.9 that I had ordered, and the focus throw from 1 meter to infinity I measure to be > 17cm, compared to about 8cm for the Rokinon 85/1.4 (and actually, the Tak focuses down to 0.85m, so the total throw is even longer). And I do find it much easier to nail the focus (and maybe it also helps that one can focus this lens while stopped down, avoiding the issues that have been reported about the Samyang).

Maybe it is a personal thing, but I find it much easier to focus accurately (if not quickly) with a longer throw.

[Laurentiu Cristofor]

And I do find it much easier to nail the focus (and maybe it also helps that one can focus this lens while stopped down, avoiding the issues that have been reported about the Samyang).

As mentioned earlier by excanonfd and byrd - you can focus the Samyang stopped down too, by using the optical preview feature of the higher end bodies (no such luck if you're using K-x/K-r).