Pentax ME-F ME-F Manual - Page 30

IMPORTANT: When contrast and lighting are insufficient for focusing, the motor will turn back and forth slowly. If this occurs, stop focusing immediately to avoid wasting batteries. • 26 On some occasions you will have to focus manually While your auto focus system is extremely accurate, there will be occasions when you will have to focus manually. When manual focus is required both LEDs inside the viewfinder light simultaneously (or flash depending on lighting conditions), informing you to focus manually. For manual focus, turn the front of the lens barrel and focus in the conventional manner with the split-image, microprism or entire focusing screen as indicated on page 38). These situations arise mainly when lighting is insufficient or contrast is too flat for the sensor to read the subject. Examples include photographing indoors in dimly lit room, outdoors at dawn, twilight or in heavy shade or overcast. (EV 5.5, at ASA 100, 1 sec. at f/6.7). Subjects without contrast, such as a white wall also present a problem, as do excessively bright subjects, strong backlighting, fast moving subjects, very fine patterns or lines, and subjects with extreme contrast lover EV 17.5; 1/500 sec. at f/19). Note: Even with subjects lacking contrast, the system can sometimes be made to work if some mark or distinguishing feature of the subject is placed in the center spot of the viewfinder, such as the bicycle tire in the top photo.