Wikipedia:Reference desk/Archives/Miscellaneous/2017 October 23

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October 23

Details re Camp Base in Kisangani, DR Congo

In DR Congo there is a national military facility known as "Camp Base" in Kisangani. Does it have another name? (i.e. less vague). When was it established? What is the name of the department that runs it? Scholarly references would be appreciated, if possible. Photos here. Thanks. -- M2545 (talk) 13:26, 23 October 2017 (UTC)

The facility seems to have only that name. Serious media sources in both French and English use the name "camp Base", e.g. [1], [2] or [3]. It is a military camp of the FARDC (i.e the national military). Finding out when it opened might be a challenge though. --Xuxl (talk) 18:37, 23 October 2017 (UTC)

The army base in Kisangani, going back to Belgian times, was known as Camp Sergent Ketele (to the east of the city centre, on the road to the airport - [4]). I am unable to locate a map showing Camp Base, so cannot tell if this is the same site, or a new location. This article talks about an agricultural project at the camp, and describes it as outside Kisangani- [5] - which suggests it may not be the same site as the old military base which would not have had sufficient land available. Wymspen (talk) 12:50, 24 October 2017 (UTC)

Thank you, Xuxl and Wymspen, for the information. -- M2545 (talk) 17:39, 25 October 2017 (UTC)

Problem with Olympus digital SLR camera

I have a strange problem with my Olympus E-M1 OM-D digital SLR camera. Often, pictures taken with a short lens focal length (shorter than 18 mm) are actually stored with exactly half of the light they were taken with. The images appear severely underexposed, with the pixels having only half the brightness they were supposed to have. With longer focal lengths, images taken with a shutter speed up to 1/200 s appear normal, but images taken with shorter shutter speeds are overexposed, the shorter the shutter speed, the more they are overexposed.

This problem occasionally goes away and then comes back, on its own accord. I usually have done nothing that would cause the problem to go away and nothing that would cause it to come back. I think it's a problem with my camera's electronics but I don't know what is wrong with them.

Has anyone else had similar problems? Does anyone know what could be causing this? Or does anyone know what would be a better place to ask? JIP | Talk 18:34, 23 October 2017 (UTC)

A natural place to ask is the Olympus support site. It offers here instructions, brochures, FAQs and software downloads for your camera. Blooteuth (talk) 19:03, 23 October 2017 (UTC)

I agree that it sounds like a problem with the electronics. Since the mechanical and optical components are a large part of the price of such a camera, perhaps they can replace the electronics for significantly less than replacing the entire camera. That, or just live with it, checking each pic and adjusting as needed. This approach would be annoying, but less expensive. StuRat (talk) 19:06, 23 October 2017 (UTC)

Just a stupid question. Are you shooting on Auto etc? 18 mm is pretty wide angle and it may be exposing for the total reflectance . Making your subject appear over or under exposed. Thus, some times it gets it right and sometimes wrong. Like, if one is shooting horizontal on wide angle one is going to capture a lot of sky and that can cause 'apparent' under exposer by confusing the sensor, like when shooting a snow scene. Being digital, it is non-expensive to immediately find this out. Switch to Centre-weighted and scan the scene. Then expose for the 'subject' and see if it makes any improvement. These are good cameras, they should do what you tell them to do. These days the 'electronics' are very reliable – go for the simplest explanation first. Aspro (talk) 19:31, 23 October 2017 (UTC)

I think it must be a problem with the electronics. The camera has an electronic viewfinder, and the image I see through it is what it is going to store in the image. However, once I press the shutter release button, the image that appears as actually stored is half the brightness of the image I saw in the viewfinder. This happens regardless of the conditions I take the picture in. I explained the situation to my father and he thought I was simply setting the lightning conditions wrong. I then showed him the problem. I put the camera on live preview mode and focused it at a setting. The image we saw on the preview appeared all OK. Then I pressed the shutter release to actually take the picture. The image that was actually stored had exactly half of the brightness of what we saw in the live preview less than a second ago. JIP | Talk 20:08, 23 October 2017 (UTC)

It appears that your camera has better than Centre-weighted as it also has Spot. metering Spot metering Try that setting for very wide angle (less than 50 mm)– and experiment. The preview just shows the jpeg (not RAW) straight from the image sensor before storing - so that is no guide. It also has a gamma display to show exposure - how to view it will be in the destruction booklet that came with the camera. Experiment. Aspro (talk) 20:36, 23 October 2017 (UTC)

The preview screen is just for composing – you know- like a view finder.Aspro (talk) 20:48, 23 October 2017 (UTC)

All this does not explain how images taken at a focal length of 18 mm or more are stored all OK, or how the problem is the same regardless of what I photograph in what conditions, or how the problem intermittently goes away and comes back again. I have tried this many times myself. I photographed the wall of my own living room at a focal length of 18 mm. The wall showed up all OK in the viewfinder, then I took a picture. The picture matched the image on the viewfinder exactly. I then zoomed the lens back to a focal length of 12 mm and the wall once again showed up all OK in the viewinder, with the exact same lighting. Then I took a picture, and the image that was actually stored had half of the brightness of what I saw on the viewfinder less than a second ago. The camera is calculating the image all OK - something goes wrong when it's actually storing the picture it just took. JIP | Talk 20:55, 23 October 2017 (UTC)

I absolutely agree that it's an electronics problem, specifically the most significant bit on the brightness channel seems to have an intermittent failure (of course, if the least significant bit had such a failure, you'd never even notice it). This is caused by interference only in certain modes, so try out every combo you can think of to try to determine what triggers it, and what doesn't. This info could either allow you to find modes that work reliably and use those, or it could be useful for the camera repairman to know which electronics need replacing. StuRat (talk) 21:52, 23 October 2017 (UTC)

I wonder why an image with exactly half the brightness is "severely underexposed." Like film, the digital sensor has some latitude for producing an acceptable image. That is like a one fstop difference, f11 versus f8. I would call two stops or more"severely underexposed" but 2 stops would be 1/4 the brightness. It would certainly look darker, but a brightness tweak in the photo app should yield a useful if not perfect image.There is more than three stops between a well lighted corner of the room I am in and the corner farthest from the window. I could shoot any part of the room with either setting and produce a pleasing image by adjusting afterward. But if the problem is exactly as described and the camera is under warranty, I would send it in for repair, along with the problem lens. If out of warranty I would check pricing from the authorized repair center or other reputable repair centers. Edison (talk) 21:01, 25 October 2017 (UTC)

Clarkvision.com tested a film and a digital camera over a wide range of under- and over- exposure. The digital camera recorded an excellent image over a very wide range of fstops over and under the meter-indicated value. A good image could be gotten from a severely underexposed image than a severely overexposed one. Edison (talk) 21:14, 25 October 2017 (UTC)

• Edison, StuRat, I'm curious to know in what way this question has anything to do with Wikipedia, and why we encourage such questions. Kudpung กุดผึ้ง (talk) 00:47, 28 October 2017 (UTC)

• I referred them to out article(s) on LSB and MSB, and tried to send them to our our article on intermittent failure. Since that's a redlink, it looks like we need, at the very least, a redirect to the correct article name. Thus, the Ref Desk has exposed a Wikipedia deficiency, one of it's beneficial functions. StuRat (talk) 01:01, 28 October 2017 (UTC)

• I just did some research, and it looks like our article is named intermittent fault, so I will now add a redirect to that article. StuRat (talk) 01:04, 28 October 2017 (UTC)
• To answer Kudpung's first question, the OP is a Wikipedia admin who has uploaded thousands of images to Wikimedia Commons. Helping them with their camera problems may not be a typical Reference Desk task, but it definitely is beneficial to Wikipedia/Wikimedia. —Kusma (t·c) 19:51, 28 October 2017 (UTC)