I think it is far more important to be able to actually focus exactly than to shim it. Sure if you have q back which is completely out of line you need to do something but, I know both my P65 and old P45 are good enough, so that I dont see any problems. However I can see a huge difference between the focus of 22 or 28 meters. Especially at f5,6 or 8
if you look at the resolution of Alpa's new "high precision focus rings" you will find the indications will do for most purposes...
... however the much higher resolution of Arca's focus ring is certainly an advantage re the handling.
Also re even higher precission (if required).
Well... lets define there is depth of focus which is between sensor and lens, and that DOF and focus point occurs on other end of lens...
Thus for wide angle lens depth of focus is way small (it is larger for longer lens), thus is that reason to shim back also for perfect parallel, as well as correct depth of focus?? Simply because depth of focus for wide angle is so very small, thus any error on it will make impact.
Thus, is it possible to shim this on also Cambo and Arca?
on the Arca you don't have to. The focus indication on the Arca is linear and it doesn't show the distance in meters (or feet)... it does show certain numeric values that translate to a certain distance (they provide tables for each lens to translate distances into the respective values). So once you know the deviation of lens & sensor (let's say it's for instance 3 numeric values) you can use that offset for any lens at any distance.Thus, is it possible to shim this on also Cambo and Arca?
So you don't shim the back... you actually just "shift" the numeric values on your tables :-)
On other tech cameras you can adjust the lenses. I've once outlined how you can do it here: http://forum.getdpi.com/forum/showpo...postcount=4572
You'll have to see if the outcome is still appropriate for focussing on the groundglass (if you use the groundglass for focussing at all...). On my kit the groundglass is still accurate for focussing.
But if the lenses require large adjustments the groundglass might be off. In this case you would also have to re-adjust the groundglass (for instance with shims).
So on an Arca or Alpa it's much easier to achieve the required spacing of lens + sensor. However, basically it's also possible to gain the same accuracy on other cameras.
Thus is it correct to say that Alpa would be the only for which it would be possible to shim the back for sensor to be perfect parallel to the camera, and the Alpa camera is from factory at such strict tolerance as to say it is perfect parallel to lens plane (or each lens actually perfect from factory and by Schneider/Rodenstock calibrated as to be perfect parallel to camera)? And for all others it would take to shim each lens to achieve same?
However... on the others (Arca, Cambo etc), when turn the back 90 degrees... shimming would thus no longer be perfect correct, right?
I'm still laughing .
Luckily I actually have REAL clients that are extremely happy with me delivering these very high resolution images to them. At this point it is a demand they know what I am showing up with at the door going to there shoots and I am getting more work because of it in certain ways. These are corporate clients that have 5 shooters they use frequently. I know it is not just my gear but me as the shooter but it gives me a edge on the competition. This is real and not some fantasy crap that we often read.
Case in point and I even hate to admit this but stupidly I lost ALL my final outputs to clients on my Drobo. I accidentally formatted the Drobo. Now i always had the Raws on backup disks but the final image drive was also screwed. This is not pleasant to admit but I had all client delivered images on DVD as well and I always made a backup DVD. I have yet to fully recover from this and 2 weeks ago my website went down as the hosting company went belly up or something. So now I am forced to go through hundreds and I mean hundreds of DVD and recover the Final Tif images to get images back to use for the web site but also doing double duty to get these images back on the Drobo. I am cherry picking and already have 70 gbs back up on the Drobo and going through hundreds of images throughout the years with different gear. My point is here is i can see the differences between the cams that i shot. It is not much of a stretch to see what was shot on MF when comparing it to the quality of others and yes my processing has certainly gotten to expert levels for sure as we all learn over the years. My point is sure these MF images are very very good and for me clients are wanting it. I have very smart clients that see and understand the increase in the images.
But my Sony is damn good too for certain jobs so it all comes down to what needs you have . I don't have to prove the MF is a better file than 35mm and why should I . My clients are happy I am happy why argue with that. I honestly read some threads and say to myself WHY go through all this crap when most of these folks never even shot a MF system in there life. I am not saying MF is the king of the road and going to run everyone off it either. End of day who cares. All I care about is delivering the best that i can to the best of my gears abilities and mine. Its not about the gear it is about the image and that gets so lost in so many threads. Okay back to more DVD's and please remind me occasionally how much I hate DVD's and how smart I am to stay away from the holy wars.
Photography is all about experimentation and without it you will never learn art.
Nope... Alpa and Arca have a different approach but basically can achieve the same accuracy. On both you can't adjust the perpendicular alignement - only the lens-sensor distance. I've outlined above how you can achieve the same on other cameras... but again only for the lens-sensor distance.
I have to say that the parallelism on my Cambo WRS is dead on. You can easily check the alignment of camera & sensor if you use large movements and check focus at infinity and then turn the digiback 180° and shoot at the same large movements. If the outcome is the same (i.e. if the spread of sharpness is the same...) the kit works as supposed to. If not... it could also be the sensor that is tilted (or the lens).
I certainly think that Alpa cameras are exceptionally made... no doubt about that! I just don't have any accuracy issues with my WRS... therefore I have no reason to trash my kit and buy an Alpa. I would take an Rm3D anyway if I'd switch the platform one day. Personal preference...
thanks for all the info about focus accuracy...shimming and work arounds between the various camera makers
This is great stuff to be aware of...thanks everybody
Was wondering why the only discussion of Mr. D's article is on this forum
"Perfection is not attainable. But if we chase perfection, we can catch excellence."
Thanks, I'd never seen that section before.
Just assumed it would be in the MF section and thought it strange it had gone unmentioned when there was such a pile of kindling.
Hadn't seen that thread either ... thanks for the link. Wow, it's just my opinion, but I honestly could only skim through it ... reading it is like dying a slow, agonizing death from a thousand paper cuts.
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.
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...
In general well worthwhile to check out that video as complement to article on LuLa;
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.
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. :-)
Godfrey - GDGPhoto Flickr Stream
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!
Last edited by GrahamWelland; 26th December 2010 at 11:28.
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 :-)
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 ?????
Life is an ever changing journey
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..
I am not a painter, nor an artist. Therefore I can see straight, and that may be my undoing. - Alfred Stieglitz
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.
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!
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!