A question about Manual Focus


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freecloud

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Dec 9, 2005
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#1
Does short sight affect focusing? I am a little bit short sight.
Last night, when I shot some chairs outside from my house using manual focus, the object looks very clear and sharp, however, the photo is blurred. But the object is much clearer when using auto fucus.

How do you perform the manual focus? I want to use manual focus since sometimes the auto focus is too slow. Could anyone give some tips?

Thanks!
 

#2
freecloud said:
Does short sight affect focusing? I am a little bit short sight.
Last night, when I shot some chairs outside from my house using manual focus, the object looks very clear and sharp, however, the photo is blurred. But the object is much clearer when using auto fucus.

How do you perform the manual focus? I want to use manual focus since sometimes the auto focus is too slow. Could anyone give some tips?

Thanks!

Not sure what you mean by "much clearer" I look at the keyword here and that is "NIGHT" I guess you handheld your camera and test in low room light. The blurring could be your handshaking while trying to manually focus while holding your cameras to shot as oppose to holding the camera firm while you let AF do its work and you proceed to click the shutter.

You want to be sure? Mount your camera on a tripod and reshoot again or test your shooting in the day time in bright light at a shutter speed of at least 1/250 shutter speed.

Short sightedness is not a problem since you can see the image as being clear & sharp in the viewfinder. Cameras like the Nikon D70 has a built-in feature that let people adjust the viewfinder focus to suit people with short or long sighted problem. Can't recall the name for this feature at this time.
 

Feb 10, 2004
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#4
When you use AF, adjust the diopter so that it looks shape thru your viewfinder. You might also need to change to a focusing screen that is more suitable for manual focus.
 

freecloud

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#5
sammy888 said:
Not sure what you mean by "much clearer" I look at the keyword here and that is "NIGHT" I guess you handheld your camera and test in low room light. The blurring could be your handshaking while trying to manually focus while holding your cameras to shot as oppose to holding the camera firm while you let AF do its work and you proceed to click the shutter.

You want to be sure? Mount your camera on a tripod and reshoot again or test your shooting in the day time in bright light at a shutter speed of at least 1/250 shutter speed.

Short sightedness is not a problem since you can see the image as being clear in the viewfinder. If not, camera like the D70 has a built-in feature that let people adjust the viewfinder to suit people with short or long sighted problem. Can't recall the name for this feature at this time.
thanks for your reply.

I used tripod and the focal length is 200mm. I intentionally used these two focus modes and compare the outputs. Yes, it was at night and the light was not good. I may need to test it again and test it at day time too.

What i am afraid of is that the eye is not as much sensitive as the camera when doing the focusing, especially for the long focus length. The following are the two sample photos:

#manual focus



#auto focus

 

freecloud

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Dec 9, 2005
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#7
my_photography said:
When you use AF, adjust the diopter so that it looks shape thru your viewfinder. You might also need to change to a focusing screen that is more suitable for manual focus.
what does "a focusing screen" mean? is it a screen that will split the object if not focus well? My camera is EOS 10d and to my knowledge there is no this kind of screen in the market. I may have to make one by myself?
 

Jan 23, 2005
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#8
freecloud said:
what does "a focusing screen" mean?
A focusing screen is the matted glass/plastic screen that the image is projected on. You view it then via the magnifier built into the viewfinder of 35mm SLRs and most DSLRS. Some camera models (I don't know about the 10D) may allow to exchange the screens for other types, e.g. those using split image/microprism fields which help immensely in manual focusing.

With the trend to autofocus SLRs, manufacturer's priorities for focusing screens have changed. Screens that are good for focusing are more matted and tend to appear less bright. Since autofocus SLR viewfinders start out with 40% to 60% less light compared to manual focus cameras (the remainder of the light being used for the AF system), manufacturers opt to go for brighter screens that are not very usable for manual focusing. On top of that, the average viewfinder magnification has also decreased, plus the frame size of many DSLRs is smaller. All this makes accurate manual focusing very hard. Even low-end SLRs in the outgoing manual focus era used to have vastly superior viewfinders.

Some DSLRs (e.g. certain Olympus models) may even omit a focusing screen altogether (or opt for an useless all-clear screen), making manual focusing/focus control impossible. Without a proper screen, the eye can accomodate and the viewfinder image will always appear in focus (unless you use parallax focusing, e.g. in micro- and astrophotography).
 

d7t3

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Oct 3, 2002
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In the Shepherd's hands
#9
generally, adjust the diopter so that the data readout at the bottom of the viewfinder looks sharp.

then, for manual focusing, adjust the lens till the desired object appears the sharpest.

sometimes it's just hard to focus manually. when using wide-angles on my d70, it's impossible to be sure of sharp focus.
 

freecloud

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Dec 9, 2005
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#10
LittleWolf said:
A focusing screen is the matted glass/plastic screen that the image is projected on. You view it then via the magnifier built into the viewfinder of 35mm SLRs and most DSLRS. Some camera models (I don't know about the 10D) may allow to exchange the screens for other types, e.g. those using split image/microprism fields which help immensely in manual focusing.

With the trend to autofocus SLRs, manufacturer's priorities for focusing screens have changed. Screens that are good for focusing are more matted and tend to appear less bright. Since autofocus SLR viewfinders start out with 40% to 60% less light compared to manual focus cameras (the remainder of the light being used for the AF system), manufacturers opt to go for brighter screens that are not very usable for manual focusing. On top of that, the average viewfinder magnification has also decreased, plus the frame size of many DSLRs is smaller. All this makes accurate manual focusing very hard. Even low-end SLRs in the outgoing manual focus era used to have vastly superior viewfinders.

Some DSLRs (e.g. certain Olympus models) may even omit a focusing screen altogether (or opt for an useless all-clear screen), making manual focusing/focus control impossible. Without a proper screen, the eye can accomodate and the viewfinder image will always appear in focus (unless you use parallax focusing, e.g. in micro- and astrophotography).
Thanks for your nice reply.
do most of the experienced photographers usually use auto focus or manual focus? do most of them use split image screen in order to accurately manually focus? It is really very tiring for my eyes to manually focus, yet not easy to get accurate focus.
 

Apr 12, 2005
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#11
Short-sightedness (myopia) and long sightedness (hyperopia) definitely affects our judgement of whether it's in sharp focus by the camera which is not suffering from any of those.

The use of diopter adjustment would be useful for manual focus only if it corrects the eye perfectly.

Manual focus is also difficult if you wear glasses to shoot because your spectacles may not perfectly correct your eyesight and also they will shift as you try to focus manually by seeing through the viewfinder.

I'm suffering from short-sightedness as well as slight long-sightedness and when the diopter corrects my short-sightedness, it worsen the long-sightedness and vice-versa. So I only use manual focus if the camera is unable to focus on my subject (such as birds or animal in a cage or a dark object against a dark background or a white subject against a white background etc.). Sometimes I auto-focus on a subject at similar distance, lock the focus and then recompose the shots so that my subject is in the right place in the frame.

Even with perfect eye sight, I don't think we can judge the sharpness from a small picture in the viewfinder. The camera does a much better job in that by using auto focus. In many occassions, the picture may look sharp in the viewfinder or LCD but when we view it on our computer, it's not as sharp.
 

lsisaxon

Senior Member
Nov 29, 2004
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#12
d7t3 said:
generally, adjust the diopter so that the data readout at the bottom of the viewfinder looks sharp.

then, for manual focusing, adjust the lens till the desired object appears the sharpest.

sometimes it's just hard to focus manually. when using wide-angles on my d70, it's impossible to be sure of sharp focus.
Wow. Tell me about it! Try shooting stars with the lenses nowadays which doesn't stop on infinity! I can't even see anything on the D70s finder, let alone focus. :) And AF is totally useless on a clear night sky.
 

#14
I am not sure how diaopter, short-sightedness (myopia) and long sightedness (hyperopia) has anything to do with focusing. I have both the above. :) I have no problem with AF and MF.
I use a 10D, whether you are in AF or MF, once the focus is achieved, the focus indicator - the green LED at the bottom right side of the view finder data will light up.
 

freecloud

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Dec 9, 2005
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#16
Ris Goh said:
..... someone selling ready made split-image focus screen here for 10D...

http://forums.clubsnap.org/showthread.php?t=155982&highlight=screen

.... but for me I prefer to DIY :bsmilie: cheap and good (if not better)....
Hi, could you kindly tell us how to make DIY one? which screen is good for making split-image screen for eos10d?
 

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