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Interesting MF digital article over at LuLa from Mark Dubovoy
- Thread starter GrahamWelland
- Start date
Here you go -- however fair warning, almost enough banter to make your eyes bleed reading it: http://www.luminous-landscape.com/forum/index.php?topic=49728.0
billbunton
Subscriber Member
I have to admit I'm getting more and more tired of LL. I hadn't seen this thread, but frankly after some of the others I'm kind of glad I hadn't.
MGrayson
Subscriber and Workshop Member
I discovered getDPI during a fit of deep despair brought on by LL and it's treatment of dissenting opinion. The contrast with this site's decency and good humor is black and white, night and day, Zone I and Zone VII ( I forget, how many zones are there again?)
Even if you all talked me OUT of a large MF purchase.... For now, anyway...
:ROTFL::ROTFL:
Matt
Even if you all talked me OUT of a large MF purchase.... For now, anyway...
:ROTFL::ROTFL:
Matt
For Alpa, Mark Dubovoy on Smibs.tv says "... also if the sensor is not exactly perpendicular to the optical axis but it is a little cock-eyed, you can push one corner out because there are corner shims..."
In general well worthwhile to check out that video as complement to article on LuLa;
http://download1.smibs.tv/FAPW/FAPW-Episode15.mp4
Regards
Anders
stephengilbert
Active member
Anders,
Far be it from me to disagree with Mark Dubovoy, but I have an ALPA, and an ALPA shimmed adapter, and I have never seen any reference to shimming to correct a lack of parallelism. ALPA shims correct the distance between the lens mount and the sensor, and assume that the two are parallel.
I believe Thomas is right. I'd like to see a citation to ALPA saying anything about shims to correct a lack of parallelism.
Steve
Far be it from me to disagree with Mark Dubovoy, but I have an ALPA, and an ALPA shimmed adapter, and I have never seen any reference to shimming to correct a lack of parallelism. ALPA shims correct the distance between the lens mount and the sensor, and assume that the two are parallel.
I believe Thomas is right. I'd like to see a citation to ALPA saying anything about shims to correct a lack of parallelism.
Steve
Godfrey
Well-known member
The article reminds me of a 'once upon a time' engineering meeting where the project manager first says that "most of the business issues of our products cannot be solved by technology" and then goes on to delineate 25 technological solutions to the business issues. And then exhorts the engineers to think outside the technological box.
Nice pix however.
Nice pix however.
GrahamWelland
Subscriber & Workshop Member
Actually you certainly can shim for non-parallel alignment by cutting up the shims and placing partial shims in the corners as required. Of course you'll need to think upside down and back to front to set up the adapter (compared to the image at least). If I recall correctly the OptechsDigital video discusses doing this also - http://www.optechsdigital.com/Videos.html - hmm, just checked and it's not covered here but I know it's certainly possible if you need that level of critical adjustment. Just be prepared to buy a spare shim set!
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if so, that's cool. Even if not readily available you could certainly cut the corner pieces out of the regular shims...?*
BUT... it begs the question how to adjust the rear standard. You'd need a perfectly plane reference and you need to align the camera 100% perpendicular to that reference on every axis. That is almost impossible without highly specialized gear... we are talking about tolerances of 1/100 millimeters.
If the perpendicular alignment of the sensor is so obvious off that it is clearly noticeable in the captures I think I would rather recommend to send in the digiback to get the sensor alignment adjusted.
On the Cambo Wide RS the perpendicular alignment can be adjusted with 4 screws - but it requires specialized tools to do so. Too, I would cleraly not recommend to adjust the rear standard by yourself.
*edit: Graham was ahead of me
ptomsu
Workshop Member
Folks,
cannot help myself, but I feel I am getting tired to need to do any personal adjustments (except AF fine adjustment as known from DSLRs) for camera systems at this price level. This is something which should be included in the final package - so if you buy a kit someone cares for all adjustment necessary.
Am I totally wrong ?????
cannot help myself, but I feel I am getting tired to need to do any personal adjustments (except AF fine adjustment as known from DSLRs) for camera systems at this price level. This is something which should be included in the final package - so if you buy a kit someone cares for all adjustment necessary.
Am I totally wrong ?????
Ben Rubinstein
Active member
It would make sense with a complete unit and indeed Hasselblad do this specifically matching backs to bodies. Alpa however don't make the backs so they could justifiably say that the problem is the back tolerances rather than their body to lens architecture. Tell me if I'm wrong though..
GrahamWelland
Subscriber & Workshop Member
Well, the reality is that my dealer did all of the calibration of my Alpa & digital backs for me (twice now) and so in that respect it was included in the 'package' and good will of an excellent premium dealer. :thumbs:
Messing around doing this myself isn't my idea of fun. Actually, even setting up the AF fine tune on my Nikon isn't my idea of fun either!
Ben: I think you're right. Especially since Alpa is the only one setting up the lenses & helicoids at their facility. The only part not sourced (and highly accurately machined) by Alpa is the digital back. That said, you'd rather take it for granted that the sensor WOULD be completely accurately placed in a digital back given that it is essentially something with no moving parts and such a critical component to overall image sharpness. It's not like these things are inexpensive consumer items either! :shocked:
Messing around doing this myself isn't my idea of fun. Actually, even setting up the AF fine tune on my Nikon isn't my idea of fun either!
Ben: I think you're right. Especially since Alpa is the only one setting up the lenses & helicoids at their facility. The only part not sourced (and highly accurately machined) by Alpa is the digital back. That said, you'd rather take it for granted that the sensor WOULD be completely accurately placed in a digital back given that it is essentially something with no moving parts and such a critical component to overall image sharpness. It's not like these things are inexpensive consumer items either! :shocked:
GrahamWelland
Subscriber & Workshop Member
:thumbs: for this video, and actually the smibs.tv series in general.
Personally I do think that Mark is still somewhat over dramatic about DSLR 'defects' such as mirrors, mirror slap, sensor alignment etc etc but certainly if you understand that he is concerned about ULTIMATE image quality then it makes more sense. imho, "Good enough" is pretty darned good these days with the current crop of DSLRs!