General Question

syz's avatar

If I'm using a manual focus lens, does my far-sightedness mean that my pictures will be out of focus?

Asked by syz (36034points) January 22nd, 2016

I got a new Canon T5 for my birthday, and the “kit” that it came in includes manual focus lenses. Since I struggled mightily with my auto-focus choosing the wrong depth to focus on, I’m not upset by that. But now that I need reading glasses, I’m wondering if I’m focusing for my sight and not actual clear pictures. Help?

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10 Answers

Rarebear's avatar

Just focus it until it’s as clear as it can be—it’s the best you can do.

thorninmud's avatar

No. It’s not like looking through binoculars, where the lens of your eye becomes effectively the last in a series of lenses, each taking the output from the previous one and refracting the rays slightly. In the binocular scenario, the lenses “upstream” from your eye need to be adjusted to compensate for the refractive anomalies of your eye, so if I look through binoculars adjusted to your eye, they will be out of focus for me.

But in your camera, the light from the lens is reflected up onto a fresnel screen in the viewfinder. You’re looking at that screen, which is roughly analogous to looking at a movie screen. At the theater, the projector doesn’t need to be adjusted for people of different eyesight. What’s clear for me at the theater is clear for everybody.

LuckyGuy's avatar

No. You’re eyeballs’ optics do not affect the cameras optics. The distance from the lens to the sensor does not change. If you are having a hard time you can buy a corrective lens for the camera eyepiece. Undersize rather than oversizing. For example, if you need +2.0 diopters to read now, try a +1.0 or +1.5 diopter . That will reduce your eye’s focus acquisition time when you look between the camera and the subject.

jaytkay's avatar

As @LuckyGuy writes, a diopter can adjust the view as if you are wearing glasses.

The Canon T5 has a built-in dioptric adjustment. It’s the little +/- wheel next to the eyepiece. I believe it works just like the T3 and here’s a link.

Adjusting the Viewfinder Focus on Your Canon EOS Rebel T3/1100D

Cruiser's avatar

Reading glasses are for viewing things up close and I am assuming your ability to see in the distance is decent. If so you should have no problem getting your shots in focus. I am pretty blind without readers and can take clear picture with manual focus on my Nikon no problem. Post a couple pics when you get a chance. Here is one of mine

syz's avatar

This and this are from today (it’s overcast and very dark, with a steady sleet falling. I have literally hundreds of birds in my back yard – we’re the only house in the entire development that puts out feeders).

Cruiser's avatar

@syz You are golden as those are awesome shots especially if you used manual focus as you nailed them and having low light conditions!

rojo's avatar

@syz The backgrounds are out of focus, you must be nearsighted. ~!

syz's avatar

There’s a definite learning curve, but I’m enjoying practicing

jaytkay's avatar

You’re not simply practicing anymore. Wow!

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