5700 vs. Minolta A1: Operation Issues (Part I.3)

Started Nov 26, 2003 | Discussions thread
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Ching-Kuang Shene Veteran Member • Posts: 5,730
5700 vs. Minolta A1: Operation Issues (Part I.3)

Is this always the case? No at all. I found in at least one situation the failure rate of A1's AF system is higher or even much higher than that of the 5700. This is shooting CRT screen. The following movie shows an example. A Minolta A1 is place about 60cm from a CRT monitor. Right behind the A1 is a Coolpix 4500 in movie mode for shooting A1's monitor. Both cameras were on sturdy tripods. The A1 may lock on the screen quickly. Once the subject is locked, a beep sound can be heard and a white dot is shown in the lower-right corner of the LCD screen. During the course of this movie, I zoom out and in and refocus. Near the end of this movie, you will see the A1 failed completely which is shown by a red dot in the lower right corner of the LCD.
http://www.cs.mtu.edu/~shene/FORUM/A1/movie-1.mov (8.2mb)

How about the continuous mode? The following movie gives you an answer. In the very beginning, the A1 struggled to focus for a while. Eventually, the AF systems locked on the screen. However, when I tried to halfway press the shutter button again, even though the AF system shows the screen is locked (i.e., white dot), the EVF and LCD showed blurred images. It takes a while to correctly lock on the screen. Then, I zoomed out and in. Refocusing was successful. The second time after the lens was zoomed out and in, the AF system failed and than became successful.
http://www.cs.mtu.edu/~shene/FORUM/A1/movie-2.mov (8.86mb)

Keep in mind that the 5700 has no difficulty in focusing on the same CRT screen area at the same distance. So, I suspect that A1's AF system must have something unusual that I don't quite understand. Also note the position of the focusing cross jumps quite randomly around its initial position even though the camera is fixed on a tripod. This could mean that the CRT screen flickering may be the cause of this random move and the unusually high AF failure. But, I really don't know if it is the case and further investigation is needed.

(8) The Anti-Shake (AS) system works well, although it is not as effective as my Nikon SLR VR lenses. I am very satisfied. Details will be reported here in the future. Note that the 5700 has no such capability.

 Ching-Kuang Shene's gear list:Ching-Kuang Shene's gear list
Olympus D-600L Nikon D7100 Nikon AF-P 70-300mm F4.5-6.3G
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