@ Guy & Jamie & Sean

[Guest Bernd Banken]

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Hi all,

 

here I have a really simple question about the AWB:

 

The small opening for this feature is relatively close to the lenses, compare to other cameras.

How small is the angle in which the ingoing light will be measured?

Could it be possible that due to the color/material of the lens (black or chrome) this device will be irritated?

FE all measurements have been made with a black lens and then a chrome one with much more reflection is screwed on with the result of a different behavior of the AWB.

 

Could this happen? An easy test with black carton onto the lens of chrome could give an answer?

 

As I wrote above, just only an idea after looking into the sales folder last night.

 

Cheers

[chetccox]

Where exactly is this awb measuring device located? I don't see it.

[lars_bergquist]

Where exactly is this awb measuring device located? I don't see it.

I presume that the reference is to the little extra light meter just to the outside of the rangefinder window. But this has nothing whatsoever to do with white balance. It gives a straight metering of ambient light, to be compared to the 'inside' metering -- this is so that the software can figure out which f-stop is used.

 

The old man from the Age When They Metered Light With a Wet Finger

[chetccox]

That is why I posed the question. There is no AWB measuring device, at least not on the outside of the camera. However, if you are referring to the small round sensor, that is not what it does. It simply measures the ambient light level to determine the brightness level for the viewfinder LED's. Put your finger over it while looking through the viewfinder. Why would the software need to know the light level to determine the f stop? The lens actually closes down on the M and the internal light meter simply measures it.

[Guest guy_mancuso]

I'm not exactly sure were this is located either. Maybe I need to read the manual. LOL

[jaapv]

The AWB sensor is in the viewfinder window behind the silver. The blue dot controls VF led brightness and presumably the aperture indication in exif and vignetting correction.

[chetccox]

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If there is an awb sensor in the viewfinder, why do filters on the lens change the awb setting? There is a small led in the viewfinder that flashes red during a timed automatic exposure, but I don't think the awb sensor is located there. The lens coding gives the information for the auto vignetting and exif info (which only records the max f stop of the lens). From what I have read, the 'blue dot' is just the sensor for the viewfinder led brightness control. If you have found some other information I would appreciate a link as the manual does not address these items in any detail.

[Jamie Roberts]

My shameful admission is that I don't use AWB on the Leicas, since the DMR was terrible at guessing WB.

 

For RAW, I set the thing to daylight so I get a predictable preview, then set WB in the raw converter.

 

For JPEG, I shoot custom WB.

 

I also don't know where the sensor is !!

[Guest guy_mancuso]

Bernd read this

 

http://www.leica-camera-user.com/digital-forum/9932-green-test-10.html

[osera]

My shameful admission is that I don't use AWB on the Leicas, since the DMR was terrible at guessing WB.

 

For RAW, I set the thing to daylight so I get a predictable preview, then set WB in the raw converter.

 

For JPEG, I shoot custom WB.

 

I also don't know where the sensor is !!

 

How embarrassing for you! LOL

 

I do the same. Always on daylight with the DMR and now the M8. Easier for me to deal with on the previews and in C1.

[Guest guy_mancuso]

This sort of proofs my point for raw shooters it really does not matter becuase we always work in a program that can do that at post time as long as you have prepared yourself to do it at post

[sean_reid]

Hi Bernd,

 

I'm afraid that I don't have any knowledge that could help you on this aspect.

 

I'm also among the group that doesn't use AWB at all (on any digital camera). I set the camera to AWB for color work but ignore that entirely during RAW conversion. AWB is not good enough on any digital camera, IMHO, for critical color work.

 

Cheers,

 

Sean

[carstenw]

Chet, in LFI and other places there have been articles explaining that since the M lenses stop down directly, always and do not communicate directly with the camera, the extra blue sensor takes a second reading of the light, directly, and by comparing this with the internal light meter's reading, the f-stop can be derived. The accuracy is +/- 1 stop, due to parallax and focal length difficulties with this approach.

 

It may also control the brightness of the LEDs, as you say. That would make sense. The f-stop is not written to the EXIF, as far as I know, which may be due to this +/- 1 stop. Perfectionists.

[dhoelscher]

.. I'm also among the group that doesn't use AWB at all (on any digital camera). ... AWB is not good enough on any digital camera, IMHO, for critical color work.

 

 

The other issue ... which won't come up for months (hopefully) until all the IR/magenta-filters, streaking/blobbing issues have been resolved is that white balance and exposure are related.

 

In the DPreview's Nikon forum about 8 months ago, there was a really interesting discussion about digital photography of objects/landscapes with unusual color predominances (the example that first kicked off the discussion was of landscape pictures of Sedona, AZ [state of Guy Mancuso!] ... for those not in the know, there are magnificent vistas of very red rock in Sedona).

 

What was happening was that the pictures taken of this super red vistas were not coming out exactly right. The book "The Canyon Conundrum" talked about how even published professional photographs of Sedona weren't exactly the right colors!

 

The discussion came to discover that what was happening was the red channel in the photos was being blown (relative to the other channels esp) - and nobody knew from chimping the individual color histograms on the back of the cameras - because those color channel histograms were being generated from the in-camera JPEGs, and those JPEGs color exposure was highly dependent on the in-camera set (or auto) white balance.

 

I'm not summarizing this very well (sorry!) ... but I had similar problems photographing blue bonnets here in Austin, and having them come out purple bonnets! (the cause was definitively blowing the blue channel) (will have to recheck the IR sensitivity!) ... Anyway, I wonder whether the color channel histograms of the M8 are generated from the in-camera JPEGs, which would make interpretation of the individual color channel exposures very dependent on exactly what the white balance of the camera was set to ...

 

Don't worry about this stuff -- this is far advanced from our issues of today .... :)

 

DH

[jaapv]

If there is an awb sensor in the viewfinder, why do filters on the lens change the awb setting? There is a small led in the viewfinder that flashes red during a timed automatic exposure, but I don't think the awb sensor is located there. The lens coding gives the information for the auto vignetting and exif info (which only records the max f stop of the lens). From what I have read, the 'blue dot' is just the sensor for the viewfinder led brightness control. If you have found some other information I would appreciate a link as the manual does not address these items in any detail.

 

I get my wisdom from the extensive description in LFI. There is a sensor visible in the middle of the top, looking in somewhat from below.

[Guest guy_mancuso]

The other issue ... which won't come up for months (hopefully) until all the IR/magenta-filters, streaking/blobbing issues have been resolved is that white balance and exposure are related.

 

In the DPreview's Nikon forum about 8 months ago, there was a really interesting discussion about digital photography of objects/landscapes with unusual color predominances (the example that first kicked off the discussion was of landscape pictures of Sedona, AZ [state of Guy Mancuso!] ... for those not in the know, there are magnificent vistas of very red rock in Sedona).

 

What was happening was that the pictures taken of this super red vistas were not coming out exactly right. The book "The Canyon Conundrum" talked about how even published professional photographs of Sedona weren't exactly the right colors!

 

The discussion came to discover that what was happening was the red channel in the photos was being blown (relative to the other channels esp) - and nobody knew from chimping the individual color histograms on the back of the cameras - because those color channel histograms were being generated from the in-camera JPEGs, and those JPEGs color exposure was highly dependent on the in-camera set (or auto) white balance.

 

I'm not summarizing this very well (sorry!) ... but I had similar problems photographing blue bonnets here in Austin, and having them come out purple bonnets! (the cause was definitively blowing the blue channel) (will have to recheck the IR sensitivity!) ... Anyway, I wonder whether the color channel histograms of the M8 are generated from the in-camera JPEGs, which would make interpretation of the individual color channel exposures very dependent on exactly what the white balance of the camera was set to ...

 

Don't worry about this stuff -- this is far advanced from our issues of today .... :)

 

DH

 

 

Ithink this is the series that was being talked about

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[johnll]

According to the M8 manual, IIRC, the blue dot is for measuring light in order to adjust brightness of the LEDs in the viewfinder, as someone already said. I think it was just speculation that it might be used to estimate the f/stop, because if they did estimate the aperture, surely they'd write it to the EXIF data? Also, I doubt very much that the AWB sensor is inside the viewfinder, as it would surely have conniptions with the bright red LEDs right nearby flashing on and off. Since someone mentioned that it reacts to fliters on the lens, it's a safe bet that it's somewhere inside the body.

[robsteve]

\. Since someone mentioned that it reacts to fliters on the lens, it's a safe bet that it's somewhere inside the body.

 

Yes, the AWB sensor is inside the body, it is called a CCD:)

 

The cameras with the best AWB tend to be CMOS. I read somewhere that the CMOS is better at processing the AWB right on the sensor, while the CCD has to do it after the data is read from the sensor.

[chetccox]

I get my wisdom from the extensive description in LFI. There is a sensor visible in the middle of the top, looking in somewhat from below.

 

Can you possibly tell me what issue the blowup of the camera was in? I do not subscribe but plan on doing so, and I see that back issues can be ordered. Have you seen any on-line views of the camera? The sensor in the middle of the top of the viewfinder on my camera is the red led for the self-timer. Thank you.

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Hallo,

Look here: Interesting Leica gear

[asmith]

According to LFI , the fonction of the blue dot is to make a non-TTL measurement of the light to compare it with the TTL measurement.. This comparison estimates the aperture in use so as topermit this to be taken into account by th vignette correctin software.

Sorry for the typos.

Alwyn