These days you don’t need to know one of the important aspects of photography, that is, focusing to get a sharp image of the subject. It is done automatically by the camera. For those who have never used a manual lens before, will definitely find it a hassle to deal with when the time comes to deal with one. In the old days one needs to learn the process with the help of a few different types of focusing screens. Nowadays you don’t have that unless the camera has a changeable focusing screen.
The procedure for focusing is very easy. You just need to look at the screen, turn the focusing ring around and stop the focusing ring when the image is sharp. The trouble is, when to stop? Even with focus beep you will probably overshoot a little. What if you don’t have the time to slowly get it in focus? Easier said than done.
Here is a technique that will help you get by and get you a sharp image for wide angle lenses. You don’t even need to look at the screen for focusing. Here’s what to do;
1) Judge the distance of your subject to the camera
2) Turn the focusing ring to the maximum (the infinity mark right on top of the lens)
3) Select your aperture (depends on lighting, the smaller the aperture the better the result will be)
4) Turn the focusing ring until the infinity mark is adjacent to the aperture marking on the lens
Note: There are two similar aperture markings on the lens, they are called Hyperfocal Distance Scale. You can only turn in one direction when the infinity mark is on top of the lens. The reading on the other similar aperture marking, gives the nearest distance that will be in focus. Everything from this point to infinity will be in focus. If your subject is beyond this minimum distance, rest assured that it will be in focus. Just make sure your subject of interest is not too near the minimum distance that will be in focus.
I used this technique when I didn’t have the time to focus (also for candid snap) or when it was dark to focus. When using flashgun, choose the aperture that your auto flashgun is capable of. For manual flashgun, you need to know its strength. You have to check it out. You will probably need a bigger aperture when in the open or in a big hall, and will be able to use smaller aperture in a small room because the reflected lights that bounced off the walls help.
That’s for wide angle lenses. In general, the technique for focusing is to start from the maximum distance, infinity mark right on top of the lens. Slowly turn the focusing ring until you get the image looks sharp and then stop. At the focus point (hyperfocal distance), there will be some distance towards the camera that will be in focus and, much more distance away from it will be in focus too. It is called Depth Of Field. How deep or shallow this depth depends on the lens focal point and the aperture used. The wider the lens, the deeper it will be. It could be just in front of the camera to infinity. On the aperture side, you get shallower depth on bigger aperture and deeper depth on smaller aperture. That explains the above technique. The reverse is true for a telephoto lens, the depth of field is shallow and the longer the focal length, the shallower the depth of field will be. The idea is that, if you missed the focusing and get it slightly forward towards the camera, the wider depth of field region behind the focusing point will increase the probability that the subject will still be in focus. Especially on a telephoto lens with wide opening, this technique gives better probability than the reverse method, that is to start focusing from near distance to infinity.
I am not a professional photographer, but in my younger days I was moonlighting a lot as a wedding photographer to help subsidise this hobby of mine. It was not cheap in those days.