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Old Mar 4, 2006, 10:05 PM   #1
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The KM 50 f/1.7 AF "prime" lens does not have the "D" desination, indicating that distancedata is passed tothe KM flash for metering. Ref. KM's Gude on the 5D:


"(D) indicates the distance encoder system. When attached to the MAXXUM 5D, D lenses enable ADI (Advanced Distance Intergration) flash metering with the built-in flash and external MAXXUM Flash 5600HS(D), 3600(D), and 2500(D)."

My interest in the 50 mm lens is for low-light photography without flash. However, if I want or need to use a flash would I get better results with a (D) lens?

Thanks in advance,

Scott

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Old Mar 5, 2006, 2:19 AM   #2
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Taking into account the crop factor, your 50 mm lense is already a tele lense. Thus you hardly will use that lense with a flash. I think the ideal lense for the internal flash and also for low light is the Sigma 1.8/24 mm EX DG lense. It covers exactly the angle of the internal flash. Thus, if you take an even wider lense, you get dark corners. Sigma DG lenses also support ADI. The Sigma lense is much larger and heavier than your 50 mm lense, though. Unfortunately, you can't get the above Sigma lense with Minolta mount for a reasonable price in Germany. That's why I settled for a Sigma 1.8/28 mm EX DG lense, which I could aquire in almost new condition on Ebay for an acceptable price.
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Old Mar 5, 2006, 5:56 AM   #3
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The only D lens I have is the kit lens. So, I can't help you there. They're supposed to be a bit better for flash exposure accuracy. But, I'm not sure that's the case.

If you go with a non-D lens, just make sure to set the camera to TTL versus ADI flash mode.

The 50mm f/1.7 is a popular lens for low light use, becaue it's small, light, bright, inexpensive and sharper than you'll find in zoom.

My favorite walk around lens for existing light use is a Minolta 28mm f/2. It's a bit better for closer quarters compared to the 50mm, and it's a relatively bright and sharp lens. I don't know how the Sigma 28mm f/1.8 EX DG compares.

Now that Sigma has announced that the Sigma 30mm f/1.4 EX DC AF Lens will be available soon in Maxxum/Dynax mount soon, it's on my radar as a possible replacement for my 28mm though (because it's twice as bright as my 28mm f/2, and in some low light conditions, I wouldn't mind having the extra stop


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Old Mar 5, 2006, 6:24 AM   #4
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After all what I heart the Minolta 2/28 mm is clearly the better lense. It is also much lighter and smaller. On the other hand, I would have payed twice as much for the Minolta lense. Besides the much lower price the Sigma lense seems to have one further advantage. It supports the ADI flash system. You do not need to disable ADI. The camera automatically switches to TTL, if the lense doesn't support ADI.
Although the Sigma 1.4/30 mm is a DC lense (digital only), it weighs almost as much as my 1.8/28 mm. Thus this lense doesn't make sense to me. I better look out for the Sigma 1.8/20 mm EX DG.
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Old Mar 5, 2006, 6:42 AM   #5
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I'm not sure ADI helps that much though. I haven't seen any tests comparing flash exposure accuracy both ways. That would make a good "pet project" for someone wanting to find out.

But, I can tell you that contrary to popular belief, even older non-ADI lenses with 5 contacts still provide focus distance information, although it may not be as accurate as newer ADI (D) lenses.

I can remember some comments from Dalibor Jelinek stating something to the effect that this information is "surprisingly accurate" (I'm paraphrasing) when he was doing some testing with non-ADI lenses with newer .mrw files from a 7D).

Dalibor Jelinek figured out where Minolta puts the focus information a long time ago.

P.S.

He has some good documentation on the maker notes tags here:

http://www.dalibor.cz/minolta/makernote.htm

He's got some good documentation on .mrw format here:

http://www.dalibor.cz/minolta/raw_file_format.htm

Neither have been updated in a while though to reflect any byte offset differences with newer models.

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Old Mar 5, 2006, 7:12 AM   #6
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I don't like to post links to other forums. But, I'll make an exception this time since the details about focus distance are in a thread here:

http://forums.dpreview.com/forums/re...ssage=13177592

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Old Mar 5, 2006, 8:44 AM   #7
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Interesting observations by Dalibor. However, the basic question, whether the KM 5D/7D provides distance information to the flash also for non-(D) lenses, is stated there but not answered. As far as Dalibor's Minolta raw file format information is concerned, it is outdated and contains virtually no information specific for the KM 5D/7D raw files. If you want to develop your own KM 5D/7D raw file processing software, his information is certainly a good starting point, but you must also look at dcraw.c for important additional details.
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Old Mar 5, 2006, 9:03 AM   #8
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Yes... I would like to see some controlled conditions tests of flash exposure accuracy comparing ADI and non-ADI lenses. The 50mm f/1.7 would be a good one, since it's available both ways (as are some other lenses).

As for Davd Coffin's dcraw.c, I use it often.

I prefer the way it handles some images, especially now that he's changed the default processing to use AHD (
Adaptive Homogeneity-Directed) Interpolation.

Edit/Added:
Much of the credit for AHD in David's code goes to Paul J. Lee, whocollaborated with Hirakawa Keigo (the original co-author of AHD algorithm as part of his Ph.D thesis).

Once Paul fully understood the algorithm,he modifieddcraw.c to use it and gave a prototypeto Dave. After some comparison studies,Dave was convinced that AHDwas superior to VNG and other demosaicing algorithm. Here is one study showing differences in algoirthms

http://www.ece.gatech.edu/research/labs/MCCL/pubs/dwnlds/bahadir05.pdf

Dave converted and optimized the prototype created by Paul J. Lee, integrating it into dcraw.c versions 7.60 and later (he's continuing to refine it).


So, products using some or all of David's code to perform the raw conversion also benefit from these improvements, while adding their own enhancements and features.


Whenever I can, I try to get David raw files from new models to make sure they get added to his code, too. For example, I got him .mrw files from the 5D before it was even shipping (thanks to a reviewer in Thailand that had earlier access to the 5D than Steve did. He was kind enough to send me some .mrw files from the 5D, complete with photos of Macbeth Color Charts taken in known conditions.

Macbeth Color Charts in known conditions with different WB settings help David make sure he's looking at the right info for supporting the camera's "as shot" white balance. I've done the same thing with another model that I've had access to images from before it was shipping and also did the same thing for a KM model that doesn't even "officially" shoot in raw. ;-)

Since a lot of other raw converters base at least some of their code on David's work, the sooner he gets new models models added to his code, the sooner some of the other raw converters will support the cameras.

But, David doesn't decode a lot of the maker notes that some of the other products like MRWFormat do. David doesn't use most of this information in his raw conversion (he's only interested in things like the RGB multipliers being used for white balance if you use the -w option from command line).

So, Dalibor's work is also important for others wanting to develop third party products supporting .mrw files, giving you a lot more information about what the camera was doing from the tags in these files.


Unfortunately, Dalibor's products are a "part time" effort, since he also has a regular job. So, his informaton on .mrw files and maker notes on his site is out of date now.

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Old Mar 5, 2006, 9:22 AM   #9
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P.S.

I was just converting some images using dcraw.c a few days ago, and preferred it's output for a quick snapshot taken in my front yard, comparing it's output to Adobe Camera Raw 3.3 and new Raw Shooter Essentials 2006. It seems to have a better tonal range and default exposure compared to the other two for this image (although sometimes I prefer ACR for other images).

A Squirrel in Hiding...

Just a quick snapshot in my front yard with a Minolta 135mm f/2.8, one stop down from wide open at f/4. Converted from raw with dcraw.c version 7.84 using the -w option from command line (I haven't compiled the newer versions lately). Converted from .ppm to .jpg using Irfanview.

No sharpening or other PP for this one --- only auto downsizing by pbase (it will sharpen). Taken using the upper left hand focus point (I was just playing around with the lens).


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Old Mar 5, 2006, 11:07 AM   #10
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Yes, dcraw.c is really a great piece of software. I always wonder, from where David Coffin got all the information about the different raw file formats. Most camera manufacturers are not forthcoming at all and when they give you information, they require you to sign a non-disclosure arrangement. Unlike other raw processing software dcraw.c supports also non-Bayer mosaics and even the totally different Foveon sensor. This generality has its price. Dcraw.c is hopelessly slow. I am thinking about an own, high speed raw image rendering software for standard Bayer RGB sensors based on information extracted from dcraw.c. From todays sensors this would only exclude Fuji's SuperCCDs. While I am quite confident about the algorithms, I am yet undecided about the framework. It should be an input plugin for an image processing program supporting 16 bit color channels. Irfanview would be the natural choice, but it is only 8 bit. Developing a Photoshop plugin is impossible, because Adobe demands 200$ and additional censorship rights. Even Microsoft didn't bejave that badly in their worst days. You cannot even download the TIFF specification from their server without being a paying devoloper. Until Photoshop version 5 or 6 the SDK was free and unlimited. Then after the Photoshop plugin design was established as a dominating standard they showed their true face.
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