Dragonophile

Since people's eyes differ, I do not quite understand how manual focus works. For example, with binoculars, when I focus to make objects sharp to me, the next person to use the binoculars must re-adjust the focus to get best clarity for them. Doesn't this apply to focusing a camera lens so if my eyes are bad and I focus to them, the sensor should turn out a blurry picture? What about taking a photo with and w/o glasses? I know this is a very fundamental question but...

newsguygeorge Loc: Victoria, Texas

My Nikon D5300 has a diopter adjustment on the viewfinder, so I focus to infinity on a distant object and adjust accordingly. I don’t do this often.

larryepage Loc: North Texas area

If you both use the binoculars while looking through your glasses (corrected distant vision), you probably won't have to change anything. The focus adjustment on the binoculars is intended (primarily) to compensate for the correction your glasses provide, if you are not using them. That's why you have to re4adjust...because your glasses are different from those of your friend (meaning that your uncorrected vision is different also).

The diopter adjustment on your viewfinder is like the focus adjustment on binoculars. I generally set mine by adjusting until the display information is at its sharpest. That means that the eyepiece is set as closely as possible to my vision, and that I should see a clear image when the lens is in proper focus. Otherwise, I'll never see a clear image, even when the lens is properly focused.

rmalarz Loc: Tempe, Arizona

Cameras are quite different than binoculars. Cameras can use super-imposed image matching, split-screen, phase detection, contrast detection. Additionally, some cameras have diopter adjustment capabilities that can match a correction to one's eyesight.
--Bob

azted Loc: Las Vegas, NV.

Are you confusing the diopter adjustment to tune your eyes to the camera, with the lens's ability to focus with the sensor? Those are two different things. The manual focus operation creates a line around the object being focused and you can choose red or white to show the correctly focused area. At least that is how it works on Sony cameras. That is the focus with the sensor. If you have not adjusted the diopter to match your eyes with the sensor, then nothing will look focused correctly to you.

Longshadow Loc: Audubon, PA, United States

That's because the binocular diopter is set for you, and both eyes are being used.
To them, one eye (their dominant) is probably out of focus, so they adjust to try and compensate.

joecichjr Loc: Chicago S. Suburbs, Illinois, USA

On my Nikon, when I use manual focus, when the subject is sharp, a little green dot in the bottom left corner of the viewfinder lights up💚. Sometimes hard to stay on the subject while also looking for the dot😒😒😒😒😒

E.L.. Shapiro Loc: Ottawa, Ontario Canada

Manual focusing.

Of course, you need to set the eyepiece diopter adjustment so that you can simply correctly see the image on the focusing screen and the data in the viewfinder. You can make this adjustment with or without your eyeglasses as you prefer. Once you have it adjusted, unless there is another user of your camera or your eyesight changes, you can leave it in place.

If you have not used manual focus for a long time, or never used it before, your focusing technique is important. The method is to focus on the subject or yo selected point of focus- when you arrive at the sharp focus point, then go beyond that point and come back. It's called rocking in the focus and is especially important where there is shallow depth of field, with the use of long focal length or any situation where the critical focus is required. Once you practice and get used to it, you can do this quickly.

Most currently made camera bodies do not have many of the old-style focusing aids such as split-image or micro screen center spots.

Older lenses, that were intended for manually focusing film cameras. had more travel in their helical focusing mechanisms- this made of easier to focus control. Many of the lenses made of modern digital cameras have significantly less travel and may require more precise manipulation.

The absence of engraved depth of field and footage scales can make the scale hyperfocal distance techniques more difficult or impossible on modern lenses that are intended for autofocus usage.

I hope this helps.

JimH123 Loc: Morgan Hill, CA

There are several ways that camera manufacturers do this depending what kind of camera you have.

In the case of mirrorless, there is a LCD screen that the image is presented to. There is only one place that the image will be in focus, no matter the condition of your eyesight. In the case of the EVF, its the same deal, except now you are looking through the viewfinder at a smaller LCD screen. There are optics in the viewfinder that allow you to focus your eyes on this small LCD screen, and a diopter adjust in case your eye can't reach focus on the LCD screen. Since you are focusing on the LCD screen, there is only a sharp image on that screen when the camera is in focus. You cannot shift focus on the camera and correct for it by adjusting the diopter adjustment. Remember, the diopter adjust is to obtain correct focus of the LCD screen. And if the image is in focus on the screen, it will look in focus to your eye.

Optical view finders are much the same principle. There is a surface that the image is projected that is sharp only when the camera is in focus. This surface used to be ground glass. Don't know if that is what it still is a I no longer have OVF cameras. And the diopter adjust is used to allow your eye to focus on this surface. No chance that there will some other point you can find focus.

Another type is range finder and that is the alignment used to indicate focus. I haven't had one of these cameras in a long, long time, and I am not up on what modern cameras of this type do now.

But be assured that it is not like your binoculars. It is designed to find the focus of the camera and not your focus.

Dragonophile

Thanks for all the replies. The focusing of the diopter was one area I had forgotten about.

User ID

The simple explanation that no one has layed bare (one reply came close, but was only close, and was overly verbose) is quite simply this:

With binoculars or such, you look THROUGH the device.

You do NOT look THROUGH the camera. You’ll often carelessly *say* that you do, but you really do not.

“Looking through the camera” is merely a figure of speech. There is really no similarity to using binoculars.

(End of simple version)

••••••••••••••••••••••••••••••••
••••••••••••••••••••••••••••••••

Not so simple version:

With binoculars you actually DO look through the device. The nearest solid thing in your view is the object you’re looking at, up to miles distant.

With a camera, the thing that you are actually looking at is only 1 to 4 inches away. You ARE NOT looking at your object of interest. You are looking at a very small viewing screen right in front of your eye.

Dragonophile

I think I have got it. The image on the focusing screen/lcd will only be sharp when the camera is focused on the object(s) you desire. The diopter allows you to adjust your eyesight to get the best image you can of the screen. So if you are going to manually focus your camera, you really need to make sure your diopter adjustment is dead on. But if the camera focus is not correct, no amount of diopter adjustment can make it appear sharp.

CHG_CANON Loc: the Windy City

Keep in mind, trying to manual focus a modern auto-focus lens through the optical view finder of the standard-issue DSLR is an exercise in frustration, even with good eyesight and a properly adjusted diopter. You'll get much better results using the DLSR's Live View feature on the larger screen display on the back of the camera. From there, you can also zoom the display to a 10x magnification so you can 'see' the actual details where you're manually focusing, or even better, having the camera auto-focus the lens at that zoomed location.

If you're working with manual-focus only lenses, such as 1980s and older SLR lenses, you might instead use the Electronic View Finder (EVF) feature of a mirrorless camera. That DSRL LiveView isn't always practical as the DSLR is best attached to a tripod so the camera is held steady as you use both hands to manipulate the focus controls. With mirrorless, you can present that same 10x zoom do your eye via the EVF with the camera held in a shooting position.

tenny52 Loc: San Francisco

yeah, We older people don't trust our eye sight accuracy anymore. I don't understand why people don't use the camera's focus indication(green dot, or center dot)?

User ID

By George, he’s GOT it !!!