EF-S 18-135mm f/3.5-5.6 IS STM - Best Way To Set Focus on Infinity?

[wchettel]

I am using a Canon EOS Rebel SL2 with a Canon EF-S18-135mm f3.5-5.6 IS STM lens. Is there an easy way to set the focus on infinity when I'm using MF mode on the lens? I just want to set it and forget it.

[ebiggs1]

"...that's what autofocus is tor, isn't it?"

I would say let the camera do its thing with AF for distant airplanes, too.

[ebiggs1 · Accepted solution]

" I just want to set it and forget it."  " I occasionally like to take pics of the moon and stars ..."

That is one way to shoot nighttime stars. Set the lens to MF.  Use the widest aperture.  Focus in the day time on something you can see that is very far away and put a small piece of tape on the focus ring.  In the dark use your Liveview option to focus.

[Waddizzle]

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@kvbarkley wrote:

Uh, no. The red dot is the infrared focus mark. RTFM.

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Uh, there is a lot of infrared in the night sky.  If you focus on visible light, then the infrared will be OOF.  One mark is infinity focus for visible light.  The other mark is infinity mark for infrared light.  Practice what you preach.

[ebiggs1]

"...Canon EF-S18-135mm f3.5-5.6 IS STM lens."

Some lenses do not do a very good job at night sky photography and you have one that doesn't. If you really want to get good shots of the sky look for a more suitable lens for that purpose.

[ebiggs1]

Oh, BTW, the particulars were...................

EOS 1DX, Canon EF 16-35mm f/2.8L II USM Lens.
30sec, ISO 3200, f4.

And, yes, I know, I know this isn't the best choice lens for night sky work either but it is a typical sample and settings if you don't have dedicated astro gear.

[kvbarkley]

The "infinity mark" is the L mark in the distance scale. The line and red dot are the indicators of where focus is set. It has nothing to do with infinity.

If you want infinity focus you put the line or mark (as appropriate) on the L mark. If you want to focus at, say 5 feet, you put the dot or indicator at the 5 foot mark.

And while there is a lot of infrared in the night sky, I don't know if it is at the same wavelength of IR film.

[ebiggs1]

The red dot is used to adjust the focus if you're shooting using an infrared filter.  Nowadays it doesn't have anything to do with IR film.

10,001 anybody? 

[kvbarkley]

But its location is based on the optical properties of the lens at the wavelength of IR film.

[kvbarkley]

I take some of it back. The wavelength of IR film is in the near infrared, just like the silicon sensor.

[wchettel]

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@ebiggs1 wrote:

"...Canon EF-S18-135mm f3.5-5.6 IS STM lens."

Some lenses do not do a very good job at night sky photography and you have one that doesn't. If you really want to get good shots of the sky look for a more suitable lens for that purpose.

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Got any suggestions for a more suitable lens? I also have a Canon EF 75-300mm F4-5.6 III lens that came with my kit.