PASSTIMES | Leisure and Travel | 22
5 Tips to check the DSLR when buying 1. Camera: Dead pixels?
3. Lenses: autofocus correct?
Dead pixels mean pixels (of monitor or image sensor) that show a weird colour even in the lowest ISO, and they can never change back to normal pixels. To check for dead pixels in the monitor and image sensor, take a few overexposed images and zoom in and look for any weird pixels.
It is always annoying if all the images you take are not sharp. That might be because your lens' preset autofocus is moved. Point your camera and lens (with tripod on) to the middle point of the focus test chart (see below) and turn the largest aperture on. If the middle of the "clear range" is not at 0mm, it means your lens' autofocus system is not accurate. Although some of the advanced and professional cameras can adjust this through the camera body, it's always better to have a correct lens.
2. Lenses: everything clear? Dust inside lenses is almost impossible to get rid of. So it is essential to check whether the lens is free of oil and dust. Open both ends of the lens and put under a strong light (e.g. iPhone in brightest mode), and see if it is absolutely clear inside the lens. Even a small dot is not acceptable.
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4. Lenses: aperture all works? Try to press the "Depth of Field Preview" button all the way when you change the aperture value, and see if the aperture looks weird, especially at the largest aperture. You may find largest and second largest aperture look nearly the same – in that case, it's a bad copy lens!
5. Cameras: dust in the viewfinder? Dusts in the viewfinder and around the mirror are generally hard to clear, so it's be the best to make sure it's dust free when you buy it! Just to add a final tip – if you find your camera is not working at all, even when it is fully charged, place it in a very dry area (e.g. near heater) for a few days and it may magically work again!
http://www.dpreview.com (most updated news and archives) http://www.price.com.hk (only trust the second/third lowest price) http://www.ygdragon.net/ (not very updated price list) http://www.dchome.net (most popular forum) http://www.dcfever.com (most popular website) http://focustestchart.com/focus21.pdf (focus test chart) Google!