Photo focus question/tip

[NoTwilight]

Well, I'm still learning how to use my new digital SLR. Most if not all of the good photographers on the forums say to use manual focus. I have been doing that but have been somewhat unhappy with the results so today I've been using autofocus with batter results. My guess is my aging eyesight is not in focus with the chip. I have 20/20 eyesight or better at distance but up close I need reading glasses. I guess the latter condition is causing some out of focus.

 

Autofocus seems to be helping. Here's a photo I took this morning on autofocus and posted across the street in a VAM thread.

 

 

--Jerry

[mgoodm3]

I use manual focus but with the help of the focus light. On nikons (not sure what Canon has) there is a round dot that will show up in the viewfinder when the focus is good. It works well most of the time. One trick to use is to get the focus close and then use the height adjustment on your copystand to adjust the fine focus (if its got a crank adjustment).

 

Seems to me that autofocus commonly has a hard time at close quarters and manual is more consistent.

 

Edit: most eyepieces on SLR's have a diopter adjustment to help with eyes that aren't in focus.

[pendragon1998]

Jerry, what kind of SLR do you have? In my experience with my Nikon D70, the autofocus isn't worth a hill of beans for coin work. It's fine for everything else.

[rexcat]

Hi Jerry,

 

What DSLR are you using? Many camera companies make magnifiers that fit on over the view finder’s eyepiece and some DSLRs have the capability of changing the focusing screen, personally I’ve enjoyed using a split image screen in my cameras.

 

Also the focusing screen appears to your eye to be about 3 feet away when your eye focuses on a screen in both DSLRs and SLRs. So to be able to see a sharp focus when manually focusing a person has to be able to hold a newspaper at arms length and be able to sharply see the print, if you can easily read the paper you can see the focus of your camera. If you can’t read the paper find out want diopter correction is needed by trying out some different power reading glasses at the drug store and then use the diopter adjustment on your cameras eyepiece to even things out for your eyes.

[MikeInFL]

I use manual focus but with the help of the focus light. On nikons (not sure what Canon has) there is a round dot that will show up in the viewfinder when the focus is good. It works well most of the time. One trick to use is to get the focus close and then use the height adjustment on your copystand to adjust the fine focus (if its got a crank adjustment).

 

Seems to me that autofocus commonly has a hard time at close quarters and manual is more consistent.

 

Edit: most eyepieces on SLR's have a diopter adjustment to help with eyes that aren't in focus.

 

Mark hit the nail on the head above.

 

I use manual focus 100% of the time. Using a tripod instead of a copy stand makes for challenging focusing, but the "focust dot" helps immensely.

 

Please see the following diagrams typical views of DSLRs:

 

"Focus confirmation" on Canon (lower right):

 

"Focus indicator" (#1) on Nikon (lower left)

 

Have fun...Mike

[robertpr-migration]

Folks, the focus indicator is no better than the autofocus system itself. There is a small range in which the focus indicator is lit, and perfect focus usually falls within that range somewhere, depending on what exactly you want to focus on. The slab itself sometimes prevents a camera from focusing on the coin and the camera tries to lock onto the slab or somewhere inbetween, oftentimes. Your eyes are generally only about as good as that dot is onscreen, looking through a viewfinder.

 

If you're really going to be anal about achieving perfect focus (and I don't see any reason to not be), then you could try a system like this one. I haven't tried it but I might order it soon and see how well it works.

[NoTwilight]

I guess the 3 ft number is the most important. I'm just starting to notice that at about 3' things are less sharp than they used to be. So when I focus them to sharp, they are not really sharp. The camera has a diopter adjustment and I haven't played with it yet. Not sure how to tell how much to move it in which direction.

 

I have a Canon Rebel XTi. I forgot I hadn't posted that here yet (posted ATS). I bought it recently and have a lot to learn. I haven't had time yet (single dad) to learn the histogram or custom white balance functions which are my top priority.

 

I'm pretty happy with the autofocus. I put a couple of the dots over the coin and generally those are the ones that turn red. If they aren't the ones that turn red then I realize the camera is focusing on something else in the slab and move the slab around to get the camera to focus on the coin.

 

My copy stand doesn't have a knob to move it up and down--it is a slider.

 

Eventually I plan to move to tethered operation and I'll be focusing on a 20" screen, that should make manual focusing easy again. I agree it is best if your eyes support it.

 

Thanks for all your help.

 

--Jerry

[MikeInFL]

Folks, the focus indicator is no better than the autofocus system itself. There is a small range in which the focus indicator is lit, and perfect focus usually falls within that range somewhere, depending on what exactly you want to focus on. The slab itself sometimes prevents a camera from focusing on the coin and the camera tries to lock onto the slab or somewhere inbetween, oftentimes. Your eyes are generally only about as good as that dot is onscreen, looking through a viewfinder.

 

Yes and no...

 

While you're right about the dot's accuracy, the problem with using autofocus itself is that it often will get fooled by scratches on the holder. Using the dot to zero in on the correct focus will achieve an in-focus image 95+% of the time -- at least with my setup.

 

As an aside, understand that when you're manually focusing, you're using the most wide open aperature (and thinnest depth-of-focus), so the actual depth-of-focus will be larger if you've stopped down the lens. Most cameras have a preview feature that will stop down the lens through the viewfinder to truly let you see what your camera will. When you do, note the increase in the depth of field.

 

All that being said, I have found the autofocus indicator to be far more accurate than my eye, but using autofocus itself leads to an increase in misfocused shots.

 

Have fun...Mike

[NoTwilight]

An autofocus generalization: I use canon Point and Shoots for kid photography. I've lost/had stolen/trashed several over the years. I've tried two nikons and ended up getting rid of both of them because I got too many blurry kidshots with the autofocus. Perhaps the canon autofocus is better. I'll try manual focus with the dot.

Thanks,

Jerry