Guest Olof Posted January 10, 2007 Share #1 Posted January 10, 2007 Advertisement (gone after registration) whats the job of the M8 brightness sensor ? I think i read somewhere that with this sensor the M8 can "calculate" which apperture the actuall lens has. But what does the M8 made with these information ? Link to post Share on other sites More sharing options...
Advertisement Posted January 10, 2007 Posted January 10, 2007 Hi Guest Olof, Take a look here M8 Brightness sensor. I'm sure you'll find what you were looking for!
rvaubel Posted January 10, 2007 Share #2 Posted January 10, 2007 whats the job of the M8 brightness sensor ? I think i read somewhere that with this sensor the M8 can "calculate" which apperture the actuall lens has. But what does the M8 made with these information ? I can imagine many use for the brightness sensor. Right now it is just being used to adjust the brightness of the readout. But according to many sources, eventually it could be used to calculate the approxiamate taking aperture. This could be handy for coded lenses. Rex Link to post Share on other sites More sharing options...
carstenw Posted January 10, 2007 Share #3 Posted January 10, 2007 According to LFI it currently does calculate the current aperture for coded lenses, based on the amount of light hitting the sensor, the amount of light hitting the little blue window, and the camera's knowledge of the current lens's largest aperture. No one has been able to verify this though, as far as I recall. Link to post Share on other sites More sharing options...
manolo Posted January 10, 2007 Share #4 Posted January 10, 2007 I thought that the aperture is recorded in the exif file. Does anybody know if this is the case? Is there aperture info in the exif? Link to post Share on other sites More sharing options...
bradreiman Posted January 10, 2007 Share #5 Posted January 10, 2007 I thought that the aperture is recorded in the exif file. Does anybody know if this is the case? Is there aperture info in the exif? no the exif only shows the widest aperture of coded lenses, not the taking aperture of the shot....yet Link to post Share on other sites More sharing options...
marknorton Posted January 11, 2007 Share #6 Posted January 11, 2007 I think it's tough to do accurately, or even reasonably accurately. The sensor and TTL meter are not looking at the same thing and who knows whether they track each other in how they respond to light. Link to post Share on other sites More sharing options...
carstenw Posted January 11, 2007 Share #7 Posted January 11, 2007 Advertisement (gone after registration) Yes. Leica apparently think that the guesstimate is good to within +/-1 stop. Link to post Share on other sites More sharing options...
rvaubel Posted January 11, 2007 Share #8 Posted January 11, 2007 I think it's tough to do accurately, or even reasonably accurately. The sensor and TTL meter are not looking at the same thing and who knows whether they track each other in how they respond to light. Mark The Two meters may be looking at different fields of view but often that is more than good enough. For example a spot meter is looking at a smaller field of view than a center weighted. The two meters, while not measuring exactly the same values in all cases, will generally give a useful result for setting aperture. So why not use the measurements for applying vignetting correction? +,- 1 F stop should be good enough for that. Rex Link to post Share on other sites More sharing options...
cbretteville Posted January 11, 2007 Share #9 Posted January 11, 2007 The only mention of the sensor in the user's manual is actually "designation of parts" at the very start. The only information in the text I could find that may be releated to it is a mention on p135 that states the brightness of the VF is adjusted to the ambient brightness. - C Link to post Share on other sites More sharing options...
manolo Posted January 11, 2007 Share #10 Posted January 11, 2007 no the exif only shows the widest aperture of coded lenses, not the taking aperture of the shot....yet "yet" I hope so; in the DMR it is there and it is very useful to judge the image. Other thing that would be grate is the focal distance Link to post Share on other sites More sharing options...
rosuna Posted January 11, 2007 Share #11 Posted January 11, 2007 Sean Reid has explained in his review site (http://www.reidreviews.com) that the light sensor works, estimating the aperture. It is just an estimation, so it is not recorded in the exif file. I think this estimation should be included in the exif though. Link to post Share on other sites More sharing options...
arthury Posted January 11, 2007 Share #12 Posted January 11, 2007 Yes. Leica apparently think that the guesstimate is good to within +/-1 stop. Can't be done without a lot of pain. If the body communicate electronically thru a chipped lens, things will be a lot more straight-forward. Link to post Share on other sites More sharing options...
marknorton Posted January 11, 2007 Share #13 Posted January 11, 2007 If the figure was included in the EXIF file, you'd have endless discussion on boards like this about how accurate it is or isn't, whether someone should return their camera because one estimate was more than 1 stop out and all that baloney, so I can quite understand them not wanting to do so. Link to post Share on other sites More sharing options...
rvaubel Posted January 12, 2007 Share #14 Posted January 12, 2007 If the figure was included in the EXIF file, you'd have endless discussion on boards like this about how accurate it is or isn't, whether someone should return their camera because one estimate was more than 1 stop out and all that baloney, so I can quite understand them not wanting to do so. But I would like to have the information anyway even if it is just an estimate. The exposure itself is sort of an estimate, or should I say their is not an absolute "correct" exposure. If the estimated taking aperture was recorded in the EXIF file, an action could be written in photoshop that could correct for both reqular vignetting and cyan vignetting. That would mean that we would not be dependent on lens coding at all. Rex Link to post Share on other sites More sharing options...
sean_reid Posted January 12, 2007 Share #15 Posted January 12, 2007 If the figure was included in the EXIF file, you'd have endless discussion on boards like this about how accurate it is or isn't, whether someone should return their camera because one estimate was more than 1 stop out and all that baloney, so I can quite understand them not wanting to do so. I think that you hit the nail on the head. The last thing Leica needs is one more thing for people to complain about and fret over. As I said in the article, the information is used for vignetting correction and TTL functions. Cheers, Sean Link to post Share on other sites More sharing options...
rvaubel Posted January 12, 2007 Share #16 Posted January 12, 2007 I think that you hit the nail on the head. The last thing Leica needs is one more thing for people to complain about and fret over. As I said in the article, the information is used for vignetting correction and TTL functions. Cheers, Sean Sean Yah but if they would let the information that was gleaned by the Blue Dot be made "public" via the EXIF info, we could provide our own custom vignetting profiles. Think what fun that would be! Talk about endless discussions of the 'correct" profile. Truly camera geek heaven Rex Link to post Share on other sites More sharing options...
scott kirkpatrick Posted January 12, 2007 Share #17 Posted January 12, 2007 But I would like to have the information anyway even if it is just an estimate. The exposure itself is sort of an estimate, or should I say their is not an absolute "correct" exposure. If the estimated taking aperture was recorded in the EXIF file,... Geeks, I think it is time to take out the EXIF-readers and DNG spec and see if that information is hidden somewhere that it is not likely to be read. Most engineers, given a nice log facility, will put interesting stuff in it. The focus distance on Olympus cameras, for example, is of varying accuracy, so it is hidden in the Maker Notes section of their EXIF. Since you need to reverse-engineer Maker Notes to do almost anything of value in an .ORF file (in a .NEF or .CR2 as well, for that matter), this stuff has been found already. Can someone who knows DNG well say whether there still are MakerNotes? My understanding was that the manufacture could bring along any secrets that he wishes, as long as basic information was openly stated. scott Link to post Share on other sites More sharing options...
cbretteville Posted January 12, 2007 Share #18 Posted January 12, 2007 Scott, DNG is just a variation of TIFF v6. Tiff has it's set of tags, DNG adds a set and you can use most JPEG tags in a TIFF/DNG as well. Marker notes are alive and well in all three formats. There are several related tags in the DNG spec, "DNGPrivateData" and "MarkerNotesSafety" are two of them. First one is a tag for manifacturer's 'private' data, the second informs the reader if the MarkerNotes should be preserved along with the reste of the info when writing the file. There are also tags describing length, byte order and offsett to the marker notes. I'm working on a decoder, but it isn't done yet. - Carl Link to post Share on other sites More sharing options...
stunsworth Posted January 12, 2007 Share #19 Posted January 12, 2007 "yet" I hope so; in the DMR it is there and it is very useful to judge the image. Other thing that would be grate is the focal distance There are no electrical connections between an M lens and the body, so this isn't going to happen. Link to post Share on other sites More sharing options...
rvaubel Posted January 12, 2007 Share #20 Posted January 12, 2007 Scott,DNG is just a variation of TIFF v6. Tiff has it's set of tags, DNG adds a set and you can use most JPEG tags in a TIFF/DNG as well. Marker notes are alive and well in all three formats. There are several related tags in the DNG spec, "DNGPrivateData" and "MarkerNotesSafety" are two of them. First one is a tag for manifacturer's 'private' data, the second informs the reader if the MarkerNotes should be preserved along with the reste of the info when writing the file. There are also tags describing length, byte order and offsett to the marker notes. I'm working on a decoder, but it isn't done yet. - Carl If, in fact, the taking aperture was imbedded in some sort of private data file, would we be able to extract that information and use it to apply vignetting actions in post processing? Rex Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.