Focus - one of the most important variables
What is the minimum number of focus points a good SLR should have? Should all the focus points be cross type focus points? For many years Olympus used three focus points in a horizontal line and the middle focus point was a cross type focus point. Should a camera have the fastest focus speed in a group test? Some SLR bodies has such a colorful focus arrangement in the view finder that one cannot help think you are a fighter jet pilot when looking through the view finder. Other fill the complete view finder with a type of focus screen that its hard for any subject not to be in focus......the question is just, which one should be in focus?
Somebody wrote saying, do not fred, all you do is sharpen the image in Photoshop when the focus is not that sharp!! Front focus and back focus are being discuss in length on forums, in fact one of surest ways to sink a new SLR is to start a series of posts blaming a body for front or back focussing. Tens of followers stand ready to take pictures of obscure subjects in and around the house to post on forums, fueling the discussions of this one has a problem or that is the best.
While all these questions are typically poorly answered, most photographers continue missing the subject when doing photography. Why is that? I believe that the average reviewer has once again placed the focus on completely the incorrect subject. Take for example the time it takes for a camera to switch on and the time it needs to be ready for use. Many years and months ago when it all started in the digital world they were slow and one had to wait before the camera was ready. But today they quick, even the compacts are quick. What does one see in almost every review? Extensive measurement of start up times. Cameras are competing for the first place beating the next one up by a split second. Is it really important if one starts 0,004 seconds quicker than another? Its this absolute nonsense that confuses the average user completely. Lets take noise.....NO, I will not go there.....
What is the most important thing you need to get right, if you want to have a winning picture? I would say focus, I know some would say exposure and yes exposure is important. Fact is I can adjust exposure in post processing, incorrect focus one cannot correct, it is just not possible. Lets take a simple example. If I take a close up portrait image, where should the focus point be? The focus point should be one the eye pupil. The human brain cannot accept a poorly focussed eye in a portrait image! If you therefor lift your fancy 30000$ body with its 61,7, all cross type focus points, which one of those will you aim to the spot on the model's eye to focus on? If you one of the 98% percent users that use "automatic" focus all the time you will know that its not possible to aim the right focus point on the model's eye because the camera automatically select the focus point plus subject to focus on. The same is true for live view or for most compacts today.
I think you saw from my introduction what my opinion is. Focussing is important and there is a right way of focussing. To give you an example my camera is almost always set on one focus point only. I prefer the center focus point on both my SLR and my compact camera. The reason is with using the center focus point the photographer can accurately and fast select exactly the point in the image he or she wants as the image focus point.
Why does the camera then have so many focus points? I think it originated from photographing moving subjects in the early days. Those who does use the continuous focus function on moving subjects will know how important it is to have multiple focus points in the view finder area. In a next article I will discuss more on this interesting subject.
Siegfried
Should I?
My camera under expose or the dynamic range of my camera is not what I expected it to be. These are typical statements people make before being advised to use the “exposure compensation” setting on their camera. People complaining about dynamic range will talk about burn outs for example. Often exposure compensation forms part of so called “best settings” for camera A or camera B. The advisor will say this camera typically under expose or that one over expose.
I like to be very direct and say...guys that’s the worse advice you can ever get!!! Stay away from the exposure compensation setting on your camera and only use it when it’s really necessary!!!
Why that, you could ask? One of the reasons are, exposure is an important setting you need to get right if you like to shoot great images. For example if you under expose an image by mistake then you will create a number of other problems. Problems that are often not possible to correct afterwards on the PC. One of the most significant problems that you will see is noise in the shadow or poorly exposed areas. The second is poor data quality in darker areas. Remember the digital camera can only optimize the dynamic range and data quality of the image if the “global” exposure was set correctly. We often talk about exposing for highlights or exposing down or up. Sometimes I purposely allow highlights to burn because it could happen that specific highlights does not need to show infinite details.
What is “burn out”?
That is when the bright areas is more than what is possible to “hold” in the histogram. I know there are more detailed explanations for burn outs but decided to only refer to the histogram in this article. For more information about exposure and the histogram read the article “Exposure” in the getting started area. To make it simple, when the dynamic range of the scene exceeds that of the camera then the bright areas exceeding the dynamic range will go white and those in the dark areas, black. Both these black and white areas are parts in the image that exceeded the dynamic range of the camera. The so called burn outs can therefor turn white in color OR black. Don’t forget dynamic range also includes the shadow areas. Have you for example checked the ability of your camera to record shadow detail before buying it? If those bright areas are clouds then its often OK if they turn white. We do not always need exact detail in all the clouds areas.... Another example is street lamps in night shots. Do we need to have all the details in each globe or lamp? Yes, in some cases its important I think and in other scenes not.
Exposure Compensation, When?
As I said above, exposure compensation is a global setting. The camera will reduce or increase the exposure in all parts of the scene and not only in the bright parts. If you dial in a value of, -1EV then you basically halved the exposure or light reaching the sensor. The camera can do that by making the sensor less sensitive. We also refer to a full stop in this case. You can achieve exactly the same effect by going manual (M) on your camera and to up the shutter speed by a full stop or to reduce the aperture by a full stop. The difference is that in the latter case the setting will be used for that image and it will differ for the next image. Personally I only use exposure compensation if I already adjusted my exposure by using the right combination of shutter speed and aperture.
I hope this brief explanation gave you enough information to think a little differently of exposure compensation.