[BruceBanner]

I don't know if other lenses do this, but perhaps its a tad more pronounced with my new Samyang 85/1.4 that I received this week. Focusing on the moon this morning and I can't think of something to really photograph that's further away than the moon (stars in astro mode maybe?), but I do have to come back from max infinity focus to get the moon in focus. Is this normal, for lenses to go beyond 'infinity'?

I tend to with the Pentax A 24/2.8 for example to max out the infinity when doing mountains and such, same with the FA50mm I think as well...

Cheers,

Bruce

[jatrax]

Is this normal, for lenses to go beyond 'infinity'?

More common than not really. I have only a very few lenses that are actually at infinity at the infinity mark. Pentax A 20mm f/2.8 and Pentax A 24mm f/2.8 are both on that list.

[pepperberry farm]

my Sigma 28/1.8 will focus to infinity and beyond... usually not a big deal since it's AF...

[pentageek]

Sigma 150-500mm and Irix 15mm also go beyond infinity (mathematical paradox, by the way As jatrax has written, it was common.

[BruceBanner]

Thanks guys, I think it's just the first time I've noticed it so obviously.

So why do they go past the infinity mark then? Isn't it a little annoying? I mean when I tripod my Pentax A 24/2.8 or FA50/1.4 and want to do landscape its handy because I just tend to be in MF mode and throw focus to infinity, then I can mess about with the rest of the settings. Now with the Sammy I will have to do a couple of test shots, make sure the distant mountains and such are crisp and clean, and that's not always easy to tell on the back of a small LCD screen. I can imagine it's the kinda thing that after spending sometime with shots, you get back home and expand image properly and realise the infinity subjects are a tad too soft!

So.... is there a way to mod a lens to being in focus at infinity, and if so is it advisable to?

[ZombieArmy]

My Samyang 14mm focused so far past infinity that I'm having it serviced since it's really hard to tell what's in focus on that lens. Tbh most of my lenses focus at infinity.

[BigMackCam]

Focusing past infinity can actually be a benefit in some situations...

Manufacturing tolerances are such that a hard stop at infinity doesn't always mean perfect infinity focus. In the days of 35mm film, that wasn't such a big problem, but with high resolution digital sensors, it can be a very real limitation.

I have an absolutely wonderful Orion-15 28mm f/6 lens designed for Soviet rangefinder cameras. When I first tried it on my Sony A7II with the M39-to-E-mount adapter I normally use with rangefinder lenses, I could tell it wasn't quite getting to infinity. The significant depth of field meant that distant subjects were acceptable, but not pin-sharp. Since the hard stop isn't adjustable without modification (and I don't like to modify my lenses), I had a second adapter ground down very slightly, and I use it with that specific lens.

Lenses that focus past infinity might not offer quite the same convenience as those with a hard stop when infinity focus is required, but they work around manufacturing tolerances very nicely

[stevebrot]

Samyang 85/1.4 Focus Past Infinity?

The words "Samyang", "focus", and "infinity" in the same sentence is cause to chuckle.

The brand is notorious for having poor infinity-stop and/or focus scale calibration for their lenses. Many are easily adjusted by pushing the rubber grip up to expose the grub screws that hold the focus ring in place. Full instructions are generally available online. OTOH, focusing a small amount beyond is better than being a few degrees short.


Steve

[SteveinSLC]

Yeah, it's not too hard to adjust. I had a 14 that was short...didn't quite get to infinity. Sent it back, and the next one was past infinity, that one I just fixed.

[leekil]

Manufacturing tolerances are such that a hard stop at infinity doesn't always mean perfect infinity focus. In the days of 35mm film, that wasn't such a big problem, but with high resolution digital sensors, it can be a very real limitation.

I believe also that the "past infinity" movement was there because temperature differences could cause the lens to expand or contract, such that infinity wouldn't be infinity at all temperatures.

Though, can a lens really focus at *infinity*? Or is "infinity" just a shorthand for "far out", but it actually is *some* finite distance from the film plane?

[stevebrot]

Though, can a lens really focus at *infinity*? Or is "infinity" just a shorthand for "far out", but it actually is *some* finite distance from the film plane?

Or perhaps not so far out. A convention of collimating to 2000x the focal length was (is?) a long-standing manufacturing practice for 24x36mm format. For 50mm, that calculates to 100 meters and for wide-angles may be very close indeed.* For the OP's lens, the factory setting may have intentionally been as close as 170 meters.


Steve

* Anyone with experience adjusting infinity focus with an ultrawide will attest to the difficulty assigning infinity to any object much further away than the house a few doors down using split image or ground glass. This is true even with magnified live view.

[stevebrot]

The brand is notorious for having poor infinity-stop and/or focus scale calibration for their lenses.

I suppose I should volunteer that my Samyang 8mm f/3.5 fisheye was set with infinity at about 3 meters from the focal plane and the distance scale markings were impossibly off. I was able to adjust it out such that 1.5 meters on the distance scale is 1.5 meters from the focal plane. Of course, that level of accuracy, while helpful for getting sharp results at distance is really sort of silly given that that rule of thumb with that lens is to set it to about 2 meters at f/8 and go have fun.


Steve

[DeadJohn]

... So why do they go past the infinity mark then? ... is there a way to mod a lens to being in focus at infinity, and if so is it advisable to?

Focus past infinity allows for manufacturing tolerances and temperature shifts.

Sometimes a lens copy might go way too far past infinity due to inconsistent manufacturing, and be unable to focus at close range. That was an issue with my Rokinon 14/2.8. It was easy to adjust at home and I calibrated infinity to be exactly at the infinity hard stop. It's held up for years and I haven't noticed any temperature drift.

Samyang/Rokinon lenses have very good optics but the calibration when received new has many reports of being inconsistent.

[Pål Jensen]

85/1.4 lenses should focus past infinity.

[BruceBanner]

Thanks everyone, I guess I should just leave my Sammy 85/1.4 alone then. I live in Australia where temperature fluctuations of 20 degrees (Celsius) in a 12hr period are quite common (Winter 0-20 and Summer 20-40).