Sigma 24mm f/1.4 Art infinite focus issue

[Alpaca]

Hey everyone, I just purchased a Sigma 24mm f/1.4 Art and I found out it doesn't focus on infinity well. When I turn the focus ring all the way to infinity, the focus actually lies beyond that. Is there any way to fix this?

I thought the Sigma USB Dock might be able to fix it, but I can't really find a solid answer anywhere. I really love the lens so far so it'd be a shame to return it because of this. Any thoughts? Thanks in advance anyone!

 

[Alexr25]

I'm afraid there is nothing you can do about it. It's a "feature" of this lens, along with many others autofocus lenses that it focuses past infinity. This isn't a problem if you let the camera do the focusing but can be a real PITA if you manually focus.

 

[Alpaca]

Hm okay, ugh. As I film mostly using a follow focus this will probably become a real problem for me. Are there any lenses in the same price range that don't have this problem? I might just go with it because it has such a nice image quality.

Thanks for the reply!

 

[Derrel]

Sigma 24mm f/1.4 ART: Hard Infinity stop? NO.

 

[Alpaca]

Sigma 24mm f/1.4 ART: Hard Infinity stop? NO.

You're right that it isn't a hard stop, but the focus ring definitely hits a barrier when you reach the end. Unfortunately that barrier lies beyond the infinite focus point...

 

[Derrel]

What you want is called a hard infinity stop. That means a lens that stops its focus ring movement at Infinity, and does not go beyond Infinity.

You have a lens that does NOT have a hard infinity stop. That is pretty common these days. Many newer lenses do not have a hard infinity stop. ALL of the Nikon ED glass lenses used to focus beyond infinity...I'm not sure if all of them still do, but I expect they do.

Ken Rockwell's reviews on newer lenses include info on the presence or absence of a hard infinity stop.

 

[Braineack]

why do they allow you to focus past?

 

[waday]

why do they allow you to focus past?

To let you get to infinity and beyond.

 

[Derrel]

why do they allow you to focus past?

Well, not sure how true it is, but the "old days story" was, back in the early days of ED glass, the only lenses that had ED (Extra-low Dispersion) glass were big, long telephoto lenses, and it was commonly said that the focusing beyond infinity was to allow for thermal effects as those big lenses were heated up out in the sun....and that in order to always be able to focus to Infinity, it was necessary to build on an allowance that took into account possible expansion for heat, as the Infinity focus point shifted with increasing temperature and minute expansion of internal lens elements. Although Nikon's ED glass is not Fluorite glass, which was Canon's invention in response to Nikon's invention of "ED type" glass, Fluorite is apparently pretty susceptible to heat and cold expansion, and Canon superteles focus beyond Infinity as well. From what I have read from Thom Hogan's site: the huge "rare-earth type" glass elements that are "grown" by Canon and Nikon take months and months to formulate in the lab (12 to 18 months), and each batch of supertelephotos must have the optical formula minutely re-calculated and ground **precisely** for each, individual batch of each lens model based upon the exact refractive index of each batch of rare-earth glass, and at the time of manufacture, a few spares are made for each run of lenses. So...these big lenses do have incredibly precise tolerances/limits as far as the exact refractive index being needed for proper focusing, so it makes sense that a design that has a bit of leeway would make sense.

Not sure about this but here's a thought,1: As to shorter lenses...a lot of newer AF lenses use a focus by wire type of technology, so that might be a factor on some lens designs. This is different than a direct, mechanical system, like the old helicoid system used in manual focus lenses.

Not sure about this but here's a thought, 2: Also, I suspect there might be a useful, practical side: if the lens is focused beyond infinity, it reduces foreground depth of field, for times when the desire is to throw the focus of a picture allllllll the way toward the background, as far as can be, with the least foreground detail in focus.

 

[Alpaca]

What you want is called a hard infinity stop. That means a lens that stops its focus ring movement at Infinity, and does not go beyond Infinity.

Okay that makes sense, these kind of lenses are really great if you're filming as you don't need to worry about going past infinity. However, if almost all modern lenses don't have this I don't see the point in searching for a new lens. I might as well live with it for now and invest in better glass (or rent it) when I really need it.

Thanks for the info!