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how to manual focus?

Petrina Yyuen , Dec 28, 2008; 02:44 a.m.

how do you learn to manual focus on a dslr?
Is it difficult ?

this may seem like a very silly question. but im new.
So how do you know /learn how to manually focus?

Responses


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Neill Farmer , Dec 28, 2008; 03:28 a.m.

The simple answer would be to push the AF/MF switch to Manual (MF) and turn the ring on the lens until the image in the viewfinder is sharp, as your camera manual will cover.
But with the tiny viewfinders on crop DSLRs there is perhaps some technique to learn in order to get the best results. Choose a point on the view finder that you wish to focus on, then turning the ring wander it back and forth slightly until you get it in the middle of that sharp zone. Remember that the zone of focus will exist from in front of your selected point to behind it in roughly 1/3 to 2/3. The length of this "in focus" zone will depend on your lens settings, that is its focal length 24mm, 50mm, 200mm and its aperture settings, f2.8 a short distance, f8 a longer distance. Play around, experiment and read your manual and the odd photo guide or magazine.

Ronald Moravec , Dec 28, 2008; 04:07 a.m.

Turn the diopter adjustment to get the focus area indicators sharp. The camera is now set to your eyesight.
Then turn the lens focus ring until the subject is sharp. There may be a confirmation light to help.

Modern dslr are not made for manual focus and the screens are optimised for other charactoristics. Some buy a focus aid screen from somone like Katz Eye which has a split image focus like the old film slrs.

Colin Carron , Dec 28, 2008; 09:27 a.m.

I find that my eyesight is no longer sharp enough to get good manual focus and modern cameras are not designed to help with slow lenses and relatively dim viewfinders compared to the 'olden days' when only manual focus was avaialble.
So the other way is to use your auto focus to make sure you focus on what you want. You can do this by setting just one focus confirmation point in the viewfinder then using that to autofocus. I have the middle point selected only. You then achieve focus by half pressing down the shutter button so tha the lens focuses but does not take the picture. Keep your finger pressed like this on the shutter then re-compose the frame as you wish. This method does not work if you select AI servo mode as the camera is cntinuously focusing. Otherwise it works well.

John Schroeder , Dec 28, 2008; 11:18 a.m.

With the camera in MF mode. I focus past my subject and then slowly bring the image back into focus. I then check the AF confirmation light. If I need to shoot quickly such as with street photography I stop down as much as I can (f16 or f22) and set the focus to about 6 feet. That way everything from 4 feet to 10 feet will be sharp. This is a little difficult with zoom lenses because they are not marked with DOF scales. You have to check the data sheets provided with them or do a few test shots.

Stephen Lewis , Dec 28, 2008; 11:19 a.m.

If you have poor eyesight, particularly with aging eyes, you're probably better off using autofocus...for the reasons cited above,namely; DSLRs have screens optimized for things other than manual focus, since so few people use it, or even know how to use it...sort of like having a manual transmission option in your car.
Having stated the obvious, your best chance of using manual focus successfully on your present camera without changing the screen, is todetermine if you have a focus confirmation indicator which works in the manual mode, and is accurate. You should try several test shots, preferably from a tripod with a cable release to reduce extraneous factors. First, adjust your diopter in the eyepiece, if you have one...or put on your eyeglasses if you wear them. Take your first picture using autofocus (for comparison purposes). Shift the camera into manual mode and take your second shot manually, relying on focus confirmation if you have it. Take your third, fourth and fifth shots manually by relying solely on what you see in your viewfinder focus screen, adjusting the focus manually as best as you can. Now take three or four more shots...but this time focus slightly ahead of the object you want in focus and then slightly behind it. Now print up all your pictures, label them, and examine them. What you should discover is that you can manually focus, and if you're lucky, it will match the camera's autofocus or even be better. Second, you will learn a little about depth of field in the last pictures...if you selected a small aperture, your main object will probably be in focus in spite of your actually focusing ahead of or behind it. Now just practice, practice, practice. If you really like manual focus, consider spending the money to get a screen specifically designed for it...it will dramatically improve your odds. BTW most of my DSLR work is with manual focus, either because the subject matter demands it (macro work), or because I'm using MF lenses on a much more modern body.

Tommy Lee , Dec 28, 2008; 12:35 p.m.

Add to what others said and also to sum it up:
1. Adjust your viewfinders. Buy additional diopters if the built-in is out of your eye sight range. You can't MF clearly if you can't see clearly.
2. If you will be doing a lot of manual focus, buy the right type of focus screen. It also help to take time to learn your equipment. ie: where is the true infinity setting (some lens can pass infinity setting). When AF indicator beep/lite-up related to the speed you turn the focus ring. Know each lens you plan to use. Some focus differently then others.
3. Know your limitations. When the camera AF (or in focus indicator) can do a better job, let it do it. When you can do a better job, take over.

BTW: It take time for your CPU to catch up to the camera. In the beginning, it is normal to be worst then that digicam you use to have. A year is not too long and in a few years you can get good result and much more to be a master. Hopefully, the eyesight stay.

Godfrey DiGiorgi , Dec 28, 2008; 02:57 p.m.

I wrote about this in January 2007 on another forum ...

---- 1/7/2007 ---

It's much easier to teach focusing in person. Writing up a procedure to do it is tedious. Happily, with a digital camera, it is easier to practice without wasting a ton of film in the process.

Here's a short sequence to experiment with:

- Start easy: Pick a medium focal length lens, like 50-70mm, and preferably a fast lens. (you can do it with a zoom set to this focal length too.)

- Place a target about 2m away, separated from foreground and background. The target should be something with some surface texture to work with, or something with a mix of 6, 9, 12, 14 and 18 point font on it. Light it adequately for a wide open aperture and short exposure time (like 1/200 second). Lock in the exposure manually so it cannot vary on you.

- Get comfortable with the camera and set it to MF mode.

- Twist the focusing ring from infinity to closest focus at a medium speed. Then the other direction after a short pause. And again and again. Do it slow enough that you can watch the focus transition from blur to sharp to blur, but fast enough that the transition to critically sharp "pops" for a moment as you turn. OBSERVE the focus transition carefully, over and over again. Get a feel for how much time/how much angular displacement of the focusing ring causes how much focus transition to occur.

The trick is to look at a subject and know the lens well enough to turn the focusing at the speed which makes the sharp moment pop, and be able to stop PRECISELY at that point.

- Start trying to achieve that point of focus ... only turn in one direction and try to stop just once, make an exposure. DON'T look at it immediately on the LCD ... it helps if you turn off the review function. You want to repeat from close limit and from infinity ten times each.

- Then download the image files to your computer and sort them into frame order. Look at them, one at a time, at 1:1 pixel resolution and mark down which are in focus and which are slightly off. Try to remember for each one what you felt as you stopped and made the exposure.

Repeat this exercise until you get nine frames sharp. Then repeat it again doing 20 frame sequences until you get 19 frames sharp. Do as many as you can but DON'T keep going until you get tired: stop and take a break for a little while. The point is to plant in your finger and eye memory how fast to turn the ring and how to stop instantly when you see the point of best focus, just once.

- Once you're doing sequences of 20 shots and getting them all in focus, double the target distance with the same lens and do the same exercise over again. Once you get 20 out of 20 with that repeatedly, you can double the distance again. It gets faster as you go along. By the time you get there, you should set up two more targets so you have three ... 2, 4, and 8m ... and do a couple of sequences where you focus on each one at a time ... put it in the center of the frame so you know which you're focusing on ... and do the same sequence of 20 until you get them all in focus through the sequence repeatedly.

So now you know what it's like to focus that lens quickly and reliably, with your eye alone.

- Change the lens to a shorter focal length (say 28 to 35mm). Start at the beginning but use 1.5m as a starting point. Same rig, same target, different focal length ... the shorter the focal length, the more subtle the focus transition is to observe.

- Keep doing the sequences with shorter and shorter lenses until you get to the shortest lens you have. Realize that when you get down to the 18-20mm range, you have to accept either a slower pace or a few more erroneous focusing frames to "finish" a sequence.

This kind of skill does not take exceptional eyesight. It takes the ability to see the motion of the focus transition 'stop' or pop for an instant and the muscular ability to stop turning the focus ring precisely at that instant. I've been able to get perfect critical focus using it even when my glasses were covered with guck after a hot session on a sweaty day or I dropped them and could not stop taking photos for one reason or another. All you're looking for is that point of "pop" in focus as the image moves a tiny bit, and to stop your fingers at that moment ... you're not trying to see the details.

I'm sure that if you go through this exercise with calm motivation, you'll find your manual focusing reliability, and speed, improve ten fold in a day. I've been doing this so long and with so many different cameras that it just seems to come naturally to me. First thing I do whenever I fit an unknown lens to my camera is switch to MF and just rack it in and out from infinity to close limit focus a couple of times to "calibrate" my eye and fingers. Within a few moments of that, I'm ready ... I rarely get a bad focus, if I bother to look through the viewfinder and focus at all ...

Which is another story. ;-)

Godfrey

Bill Tuthill , Dec 28, 2008; 03:23 p.m.

In some ways manual focus is "easier" than autofocus because you can focus on exactly what you want, instead of moving the AF points around until the camera gives you what you want.
Petrina, you were asking about entry-level DSLR purchase in another thread. If you are interested in manual focus, I strongly recommend avoiding models without depth of field (DOF) preview, such as the Nikon D40 and D60. DOF preview stops down the aperture so you see the picture as it will appear in your final image, rather than with maximum aperture to brighten the viewfinder. DOF preview is a critical feature for both macro and portrait photography.

Sarah Fox , Dec 28, 2008; 10:20 p.m.

What Godfrey describes is a modified version of what psychophysicists call the "method of limits." I used it extensively in research long ago to establish auditory thresholds. When it is well practiced and executed, it is quite precise. It is the method I use myself to manually focus with a standard focusing screen, and I've found it works very well.


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