scott kirkpatrick Posted October 17, 2007 Share #21 Posted October 17, 2007 Advertisement (gone after registration) Finally, there is information in the EXIF (but concealed in the Maker Notes portion) that reveals the estimated aperture. Results for most scenes with reasonably uniform illumination are rather accurate -- the stated value tracks the actual setting in my tests with an offset of half a stop. When you cover the little blue dot, the EXIF defaults to the maximum aperture (most wide open setting) as coded in the table you can find in the firmware. This information was developed mostly by another forum member, who hasn't gone public with his results, but he shared them with Leica and got confirmation of his conclusions, and perhaps acceptance of several suggestions that he made. As for what uses the camera makes of the estimated aperture and other things that the blue dot brightness could be used for, such as flash control and vignetting compensation in the luminance channel, Leica isn't saying and probably will keep that information proprietary. scott Link to post Share on other sites More sharing options...
Advertisement Posted October 17, 2007 Posted October 17, 2007 Hi scott kirkpatrick, Take a look here What is that small circular window for?. I'm sure you'll find what you were looking for!
Guest tummydoc Posted October 17, 2007 Share #22 Posted October 17, 2007 Mr. Daniel was quite specific when he stated that it has no function other than diode brightness, citing the fact that there would be too much parallax between the cell and lens to provide any measure of accuracy, and also that the 135/2.8 and the goggle attachment for the Macro Elmar obscure the cell and therefore any computations would be impossible. When questioned as to why the M7, which also purports to have auto-dimming meter diodes, does not have a blue cell, his answer was that the M8 is much more precise. I did find that a bit incredible, after all the auto-dimming is a rather minor feature, so it seems odd that Leica would go to so much bother simply for that. It would be interesting to take a series of shots, with coded lenses, with the blue cell covered and un-covered respectively, and then see if there are any outstanding changes in parameters upon opening the DNGs in Capture One. Scot posted just as I did...it is good that someone has tested this out. Rather sad however, that Leica's official stance is once again in conflict with what has been gleaned by users. It will be refreshing if at some point Leica will cease to under-estimate the intelligence of its buyers. Link to post Share on other sites More sharing options...
scott kirkpatrick Posted October 17, 2007 Share #23 Posted October 17, 2007 Vinay, please see my note just above. You may be reading more into Mr. Daniel's response than he intended. I can tell you about one thing that it does, because i did the experiments and had the EXIF read. I can't tell you what it doesn't do. scott Link to post Share on other sites More sharing options...
sean_reid Posted October 17, 2007 Share #24 Posted October 17, 2007 According to Stefan Daniel the blue window houses a brightness sensor that does one thing and one thing only: adjusts the brightness of the viewfinder display diodes according to ambient light. He responded specifically that it does not provide any input for corrections to image parameters whatsoever. Sean, would you please name your source at Leica who gave you your information to the contrary, so I that I may foward it to Stefan? No, I will not name my sources at Leica and Stefan and I are often in communication. Stefan hardly needs to have my information forwarded to him and many people at Leica already read RR. I can tell you, generally, that my sources come from engineering, software development, product management and marketing. Cheers, Sean Link to post Share on other sites More sharing options...
sean_reid Posted October 17, 2007 Share #25 Posted October 17, 2007 Scot posted just as I did...it is good that someone has tested this out. Rather sad however, that Leica's official stance is once again in conflict with what has been gleaned by users. It will be refreshing if at some point Leica will cease to under-estimate the intelligence of its buyers. Vinay, If you'd read my article earlier this year you would have known that they've already officially confirmed, for publication, what the functions of that item are. I get "official" information, which can be published, and other kinds of information which I do not discuss or publish. Why does this appear in my review specifically? I did the groundwork needed to get an answer. I've written about the M8 in more depth than most publications or sites. Cheers, Sean Link to post Share on other sites More sharing options...
Guest tummydoc Posted October 17, 2007 Share #26 Posted October 17, 2007 No, I will not name my sources at Leica and Stefan and I are often in communication. In that case, you might ask him why both he and Ralph are unaware of the true function of the blue cell or chose to provide disinformation about it to more than one group of persons including dealer reps, and finally why the owner's manual agrees with his explanation rather than the correct one. many people at Leica already read RR. Well it's a relief knowing that they do have at least one source of accurate official information about the camera they manufacture I can tell you, generally, that my sources come from engineering, software development, product management and marketing. Hope you rely on the former three and accept the latter for entertainment value alone Link to post Share on other sites More sharing options...
sean_reid Posted October 17, 2007 Share #27 Posted October 17, 2007 Advertisement (gone after registration) In that case, you might ask him why both he and Ralph are unaware of the true function of the blue cell or chose to provide disinformation about it to more than one group of persons including dealer reps, and finally why the owner's manual agrees with his explanation rather than the correct one. Well it's a relief knowing that they do have at least one source of accurate official information about the camera they manufacture Hope you rely on the former three and accept the latter for entertainment value alone Actually, several manufacturers get good information about their cameras, as well as ideas, from my reviews and others. Of course, I'm just one of several sources out there but Canon, Leica, Nikon and Zeiss all read my site. Stefan has never given me misinformation and I don't know what exactly was said at that presentation you're discussing, etc. Also, everyone likes to pick on marketing (with every company) but my contact there has been quite accurate with his information, all in all. If he doesn't know, he says so. Of course, commercials and advertisements (for all kinds of things) mislead but that's a different matter. Cheers, Sean Link to post Share on other sites More sharing options...
sean_reid Posted October 17, 2007 Share #28 Posted October 17, 2007 I'm curious why they couldn't use it for flash exposures as well, to approximately set the aperture on an auto flash. Or use it as an auto sensor with a TTL flash in combination with the pre-exposure aperture approximation. Actually, I think it does play a role in "TTL" flash. I'd have to look back at my own article to remember. Cheers, Sean Link to post Share on other sites More sharing options...
Guest tummydoc Posted October 17, 2007 Share #29 Posted October 17, 2007 Actually, several manufacturers get good information about their cameras, as well as ideas, from my reviews and others. Of course, I'm just one of several sources out there but Canon, Leica, Nikon and Zeiss all read my site. Most definitely more cost-effective than paying their own R&D team to perform the same tests I don't mean to trivialise the usefulness of feedback from the field, and its good that there are those like yourself whose methodology has at least a semblance of validity as opposed to many of the unofficial reviews in the form of forum chatter, much of it based on obvious misinterpretation of anectodal evidence. I shall earmark yours for inclusion in my pay-site subscription budget next year...this year it's been fully allocated to porn Link to post Share on other sites More sharing options...
guy Posted October 17, 2007 Share #30 Posted October 17, 2007 I published that information early in 2007 and it is from the horse's mouth. If you'd read my article earlier this year you would have known that they've already officially confirmed, for publication, what the functions of that item are. Actually, several manufacturers get good information about their cameras, as well as ideas, from my reviews I'd have to look back at my own article to remember. Hang on, I'm confused – does Sean write some kind of camera reviews website? Link to post Share on other sites More sharing options...
sean_reid Posted October 17, 2007 Share #31 Posted October 17, 2007 Most definitely more cost-effective than paying their own R&D team to perform the same tests I don't mean to trivialise the usefulness of feedback from the field, and its good that there are those like yourself whose methodology has at least a semblance of validity as opposed to many of the unofficial reviews in the form of forum chatter, much of it based on obvious misinterpretation of anectodal evidence. I shall earmark yours for inclusion in my pay-site subscription budget next year...this year it's been fully allocated to porn I can't possibly compete with that *budget* <G>. I mean the RR articles are interesting but, em... Cheers, Sean Link to post Share on other sites More sharing options...
sean_reid Posted October 17, 2007 Share #32 Posted October 17, 2007 Hang on, I'm confused – does Sean write some kind of camera reviews website? No, why do you ask? <G> Cheers, Sean Link to post Share on other sites More sharing options...
Hookeye Posted October 17, 2007 Author Share #33 Posted October 17, 2007 Well, that myth about "diode brightness" seems wrong anyway. At least on my M8. When I cover the little circular window with my finger - the diode brightness is unchanged. Likewise if I shine a bright light into it. Link to post Share on other sites More sharing options...
rob_x2004 Posted October 17, 2007 Share #34 Posted October 17, 2007 Why doesnt someone cover it up and shoot off a card and see what happens? Link to post Share on other sites More sharing options...
lars_bergquist Posted October 18, 2007 Share #35 Posted October 18, 2007 Time to make an end to this wild guessing. Originally, Leica intended to use this sensor for two purposes. One is the only one Mr. Daniel wants to mention: adjusting the finder diode brightness. But the other was that of a substitute for the lacking working aperture information from the lens. By comparing the light falling on the shutter, with a plain brightness reading of the ambient light, it should have been possible to estimate the working aperture (the max aperture was of course known, if the lens was coded). It was found however at a pretty late stage of the testing process that these estimates were very inaccurate, and in the last moment, this value was struck out of the EXIF information. Mr. Daniel speaks the truth, nothing but the truth, but not the whole truth—by far. The M7 has is 'brigtness sensor' behind the main finder window. The M8 would have had it there too, if that had been the only intended purpose. Flash info? Pooh pooh. The old man from the Age Before the M8 Link to post Share on other sites More sharing options...
Mark_Schretlen Posted October 18, 2007 Share #36 Posted October 18, 2007 It was found however at a pretty late stage of the testing process that these estimates were very inaccurate More inaccurate than shooting a frame with an Elmarit at f/16 and having it report in the EXIF that it was shot at F1.0 ? Link to post Share on other sites More sharing options...
sean_reid Posted October 18, 2007 Share #37 Posted October 18, 2007 Time to make an end to this wild guessing Wild guessing? Have you read the whole thread? Link to post Share on other sites More sharing options...
Guest tummydoc Posted October 18, 2007 Share #38 Posted October 18, 2007 By comparing the light falling on the shutter, with a plain brightness reading of the ambient light, it should have been possible to estimate the working aperture (the max aperture was of course known, if the lens was coded). Seems like a rather over-complication, especially due to parallax, of what could've been easily accomplished TTL using the one and only meter cell. Let's say the camera is set @ ISO 160, and the meter reads a value of EV 8. That corresponds to a multitude of possible combinations of apertures and shutter speeds. Since the camera knows the shutter speed, either because it sets it itself in AE mode or because the user has set it manually and balanced the meter so the centre diode is lit, the corresponding aperture for that EV is easily deduced. The only instance it fails is if the user doesn't have the camera set to AE and doesn't adjust parameters so the centre diode is lit. (I haven't had my morning coffee so if there's a flaw in my logic, that's my excuse ) Link to post Share on other sites More sharing options...
stunsworth Posted October 18, 2007 Share #39 Posted October 18, 2007 But the EV the meter reads is going to be dependent on the aperture setting isn't it? With a handheld meter there is no aperture, so the EV is directly related to the amount of light falling on its sensor, but with an aperture the amount of light can be varied by changing the aperture, or am I missing something? Link to post Share on other sites More sharing options...
sandymc Posted October 18, 2007 Share #40 Posted October 18, 2007 But the EV the meter reads is going to be dependent on the aperture setting isn't it? With a handheld meter there is no aperture, so the EV is directly related to the amount of light falling on its sensor, but with an aperture the amount of light can be varied by changing the aperture, or am I missing something? Correct. The internal cell effectively reads aperture value multiplied by EV value, the external cell effectively reads EV. So you can calculate aperture value. Note I say effectively because the maths don't work this way, but the effect is the same. The problem is that the angle of view of the external cell is not the same as the lens based internal cell. Which is why the aperture measure is only approximate. It would be especially bad for long lenses. Sandy Link to post Share on other sites More sharing options...
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