Infinity focus on Canon 50mm 1.4 vs Tamaron 45mm 1.8

Hi there

I just had a question that was confusing me with regard to my Canon 50mm 1.4 lens and my Tamaron 45mm 1.8 SP lens.

The Tamaron is a great lens, but when I was checking the focus distance indicator I noticed it hits 'infinity' as the next marked point after 2 meters/6 feet, which was a little shorter than I might have assumed.

On the other hand, on my Canon 50mm 1.4, the focus distance indicator goes past 5 meters before hitting infinity - apparently over double the distance.

Do I assume that this means the Tamaron lens offers a smaller (significantly closer) window for precise focus before hitting infinity? Or is that not how these things work?

Many thanks

Will

Lemming51 wrote:

wew82 wrote:

Hi there

I just had a question that was confusing me with regard to my Canon 50mm 1.4 lens and my Tamaron 45mm 1.8 SP lens.

The Tamaron is a great lens, but when I was checking the focus distance indicator I noticed it hits 'infinity' as the next marked point after 2 meters/6 feet, which was a little shorter than I might have assumed.

On the other hand, on my Canon 50mm 1.4, the focus distance indicator goes past 5 meters before hitting infinity - apparently over double the distance.

EF 50 f/1.4 USM has marks for 3m then infinity. Do you mean the EF 50 f/1.8 (mk I)?

EF 50 f/1.8 - original "Mk I"

EF 50 f/1.4 USM

Do I assume that this means the Tamaron lens offers a smaller (significantly closer) window for precise focus before hitting infinity? Or is that not how these things work?

That is how these things work. To speed focus, autofocus lenses have a very compressed rotation from close to infinity focus, maybe 1/3 to 1/2 a rotation. Old manual focus lenses typically had the ring turn 2/3s to nearly a full rotation.

The distance scales are at best a crude approximation, and ultra-fine focus is generally not necessary at longer distance as the depth of field makes small errors unnoticeable at typical viewing magnifications.

The Tamron lens may or not have a smaller rotation to infinity than the Canon. Both have a range of "infinity" or far focus. On the Canons, it is from the "L" mark to the left side of the infinity symbol. (or from left side to middle of the symbol for the EF 50 f/1.8). On the Tamron the symbol is stretched a little and the far focus range is from the left side to the right side of the symbol.

Tamron SP 45 f/1.8 Di VC USD

Thank you, you are absolutely correct, it was the original 1.8 I was comparing to.

That's really useful to hear - so it's not a case of there being a comparatively smaller range of focus distances before hitting infinity on the Tamron (i.e it would still be able to isolate a specific focus point at 3 meters like the canon), it's just that those slightly-further focal distances are extremely compressed (and therefore not marked) on the focus ring relative to the older Canon lens.