Auto Focus Questions

thunderkyss

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How often do you use auto-focus? Is it something you could live without?

I've got two Nikon DSLRs in the family. My daughter's old D100 & my D3000. As you know, auto-focus is built into the body of her camera, not on mine. So, the AF lens I bought my camera with (both used a few weeks ago) doesn't "work" & I have to focus manually. I can put the lens on her camera & it works fine.

So I've been having to focus manually, and at our get together the other night, there were times I was taking several shots one after the other. Well, after reviewing the photos on a bigger screen, it appears many are not in focus. So, I'm thinking of getting an auto focus lens.

On her D100, she has three options for the focus on her camera; manual, Single, Continuous.

Are these modes built into the lens, or would I need to upgrade my camera to get continuous auto focus?
 
The three modes are in the camera body, not the lens.

The D3000 needs the motor in the lens in order to AF. The D100 uses the screw-drive if needed.
 
Manual focus doesn't work very well with small-finder cameras and slow-aperture zoom lenses...the finder image is small, and the actual manual focusing ring travel on MANY AF lenses is very coarse, and very poorly-damped...missed focus can be a HUGE problem with many,many autofocus zoom lenses. It's nothing at all like manually focusing on a 35mm SLR with a viewfinder system AND a lens, both of which were designed to BE manually focused!!! With telephoto primes, and in fact with many primes in Nikon AF mount, manually focusing can be a viable option, especially with the cameras that have larger, better viewfinders.

Generally, autofocusing is faster and more accurate than manually focusing, when using almost any AF lens, at normal distances. Under some scenarios, manual focusing can be better. A number of factors come into play. But with the small-finder, pentamirror bodies like the D3xxx and D5xxx cameras, I think AF is the way to go, most of the time.
 
I have tried manual focus with my D5100, and I would say its pretty impossible. It kind of works if one uses a large aperture to kind of guess where the focus is, then move to small apertures to get a wide depth of field. Of course its still not spot on this way. I would need a KatzEye screen for that, but that would lead to other problems (metering will be off).

There is probably a KatzEye screen for the D3000, too.

The other alternative would be to buy one of the Nikon cameras with screwdrive (anything of higher quality, no matter how old).
 
........ I would need a KatzEye screen for that, but that would lead to other problems (metering will be off).
..........


Only if you spot meter.
 
Indeed, most DSLR's don't have viewfinders that are designed to work with manual focus. The viewfinder in my 10D appears to be the same (same brightness and depth of field) at all apertures wider than about f4, so I can't effectively focus fast lenses with any accuracy.

For many DSLR's you can buy replacement viewfinder screens that more closely resemble the viewfinders from older SLR's, which supposedly facilitate manual focusing. The two viewfinder screens I know about are KatzEye and Haoda. I'd like to get one, but I've been enjoying my old Pentax SLR so much that I'd rather just shoot film for now. :)
 
....... The two viewfinder screens I know about are KatzEye and Haoda. I'd like to get one, but I've been enjoying my old Pentax SLR so much that I'd rather just shoot film for now. :)


I'm not regretting the KatzEye for my D7000. Too bad they don't have one for the D600. Yet.
 
Many don't know that the Auto Focus module is in the bottom of the camera body.

The main mirror in the camera is 50% transparent so half the light coming into the lens can go through the main mirror to a smaller secondary mirror that then directs light down to the AF module.
The AF module then uses a phase-detection system to determine which way the auto focus motor (where ever it is) needs to be driven to achieve focus.

AF is always done with the lens aperture open as wide as it will go. That is one of the benefits of using higher grade lenses that have a wider, and constant, maximum aperture. Then, if the lens is set to less than max aperture, the lens aperture gets smaller to make the exposure.
Understanding Camera Autofocus
 
Thanks for all the replies guys.

Since my last post, I happened into a Best Buy. They had a D3100 & I went through the menus. It does not have continuous servo auto-focus. They had a D3200 that did. So, I guess for that function I would have to upgrade my D3000
 
See page 42 of your D3000 User's Manual where it explains you have AF-A, AF-S, AF-C, and MF focus options.
IIRC the complete D3000 User's Manual is a PDF file on the software disc that comes with the camera.

Page 55 of the D3100 User's Manual shows it does indeed have Continuous Servo AF (AF-C), as does the D3000.
 
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You will need AF-S lenses with your camera. From Nikon:"Consumer level Nikon digital SLR cameras are designed without built-in focus motors, which allow them to be smaller and lighter than the larger, more professional models. Consumer D-SLRs that do not incorporate a built-in focus motor (and therefore need to use AF-S lenses) include the following: D40, D40x, D60, D3000, D3100, D5000 and D5100. If you own one of these cameras, then you need to use an AF-S NIKKOR lens to get the full autofocus capabilities from the lens."
 
Thanks for all the replies guys.

Since my last post, I happened into a Best Buy. They had a D3100 & I went through the menus. It does not have continuous servo auto-focus. They had a D3200 that did. So, I guess for that function I would have to upgrade my D3000

Even with the D3200, you will still need AF-S lenses to autofocus as this model does not have a built-in motor.
 
See page 42 of your D3000 User's Manual where it explains you have AF-A, AF-S, AF-C, and MF focus options.
IIRC the complete D3000 User's Manual is a PDF file on the software disc that comes with the camera.

Page 55 of the D3100 User's Manual shows it does indeed have Continuous Servo AF (AF-C), as does the D3000.

Thanks, I guess I could have read the manual eh?
 

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