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Thread: Tech cameras and IQ.

  1. #101
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    Re: Tech cameras and IQ.

    what all this points to is a shortcoming of the helical focus mounts. who makes these, and why can't they change the thread pitch to something more like 3-4mm? these new lenses have been mounted on pre-digital helicoids with a way too coarse pitch

  2. #102
    Sr. Administrator Jack's Avatar
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    Re: Tech cameras and IQ.

    Quote Originally Posted by jlm View Post
    what all this points to is a shortcoming of the helical focus mounts. who makes these, and why can't they change the thread pitch to something more like 3-4mm? these new lenses have been mounted on pre-digital helicoids with a way too coarse pitch
    That's exactly what Arca did with the RM3D John -- the helical has a 2.5mm thread pitch and minimal thread clearance -- and it's why it's on the body and not the lenses...

    The more I use this camera, the more I love it. Heck, my entire Phase DF kit may be up for sale soon
    Jack
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  3. #103
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    Re: Tech cameras and IQ.

    Quote Originally Posted by Jack Flesher View Post

    The more I use this camera, the more I love it. Heck, my entire Phase DF kit may be up for sale soon

    You mean I would have the last laugh. You will never give me that pleasure.

  4. #104
    Sr. Administrator Jack's Avatar
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    Re: Tech cameras and IQ.

    Quote Originally Posted by TEBnewyork View Post
    You mean I would have the last laugh. You will never give me that pleasure.
    Well I would if I did, but I seriously doubt it will ever come to that reality. But I do understand the sentiment!
    Jack
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  5. #105
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    Re: Tech cameras and IQ.

    Quote Originally Posted by Jack Flesher View Post
    Well I would if I did, but I seriously doubt it will ever come to that reality. But I do understand the sentiment!
    3 months and you are over it. Trust me you'll find your art slide. Its not really your style. I just know you too well. I know slowing me down would kill my art
    Photography is all about experimentation and without it you will never learn art.

    www.guymancusophotography.com

  6. #106
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    Re: Tech cameras and IQ.

    But I love tweaking knobs and spinning dials
    Jack
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    Re: Tech cameras and IQ.

    so all that cambo/alpa have to do is make a new design finer picth helical mount and offer that on their lenses. I wonder who makes those for them?

  8. #108
    Sr. Administrator Jack's Avatar
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    Re: Tech cameras and IQ.

    Quote Originally Posted by jlm View Post
    so all that cambo/alpa have to do is make a new design finer picth helical mount and offer that on their lenses. I wonder who makes those for them?
    Perhaps Milich Machining should offer a proposal?
    Jack
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  9. #109
    Senior Member Thierry's Avatar
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    Re: Tech cameras and IQ.

    Dear Jim,

    Alpa do not have to re-design a finer pitch helical mount: they are as precise as Arca's, despite what is told here and there, even more precise in some situations. It simply needs to have both cameras side-by-side and do a field testing.

    The theory presented here makes abstraction of some important facts:

    Read here what has been said from a Arca user, Post #63 and myself, Post #64 & #65

    http://www.luminous-landscape.com/fo...?topic=49894.0

    Best regards,
    Thierry

    Quote Originally Posted by jlm View Post
    so all that cambo/alpa have to do is make a new design finer picth helical mount and offer that on their lenses. I wonder who makes those for them?

  10. #110
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    Re: Tech cameras and IQ.

    with all due respect, how can the focus resolution of the alpa, if full range of rotation is less than one revolution, match the arca, which has several rotations for the same lens travel?

  11. #111
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    Re: Tech cameras and IQ.

    It can't. And yes I had both cameras side by side. And to say that it could be even more precise is just wrong. While the Alpa is a great camera, it has the same limitations and benefits from the normal heli mount.

  12. #112
    Senior Member Thierry's Avatar
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    Re: Tech cameras and IQ.

    Jim,

    No harm at all.

    Please read what the member says in Post 63, have a look at the tables provided by both, and moreover test it practically, that's what is relevant, not some theoretical values.

    Best regards
    Thierry

    Quote Originally Posted by jlm View Post
    with all due respect, how can the focus resolution of the alpa, if full range of rotation is less than one revolution, match the arca, which has several rotations for the same lens travel?

  13. #113
    Senior Member Thierry's Avatar
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    Re: Tech cameras and IQ.

    Dear Christopher,

    One often forgets to mention that the Arca helical ring DOES NOT turn 5 rotations for all lenses, in fact much less with shorter lenses. And in this situation, with these lenses, look at the focus tables provided.

    Best regards
    Thierry

    Quote Originally Posted by Christopher View Post
    And to say that it could be even more precise is just wrong.

  14. #114
    Sr. Administrator Jack's Avatar
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    Re: Tech cameras and IQ.

    Quote Originally Posted by jlm View Post
    with all due respect, how can the focus resolution of the alpa, if full range of rotation is less than one revolution, match the arca, which has several rotations for the same lens travel?
    Quote Originally Posted by Christopher View Post
    It can't. And yes I had both cameras side by side. And to say that it could be even more precise is just wrong. While the Alpa is a great camera, it has the same limitations and benefits from the normal heli mount.
    Correct, it cannot -- and very well stated on all points. All good systems, but the heli-mount has limitations.

    Quote Originally Posted by TH_Alpa View Post
    Jim,

    No harm at all.

    Please read what the member says in Post 63,
    Thierry,

    Just so you know, it is j l m for John L Milich in small letters, not "j *i* m" The next thing you should know is John is a precision machinist that also fully understands the physics of optics.

    Re post 63: While it is correct that not all lenses use all 4 rotations for normal use on the Arca, the fact remains the helical itself is of very high quality with a finer thread pitch and larger barrel diameter than the typical (including Alpa's) helical. Both of those aspects create a much finer vernier on the dial, and the finer the vernier, the higher the precision. It really is as simple as that. Now we can debate practicality of having that in use for typical tech cam photography, but as somebody who has used both, I'll take the finer vernier over a faster one 8-days a week -- though I respect other's opinions may vary.

    PS: John, I can edit your name to caps or anything else you want without losing your post integrity.
    Jack
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  15. #115
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    Re: Tech cameras and IQ.

    the fineness of focus adjustment is a simple matter of the thread pitch; the finer the pitch (smaller number), the finer the focus. the arca pitch seems to be the smallest at 2.5mm/revolution.
    alpa and cambo are not that fine


    jack: i kind of like the ambiguity all those verticals give in my name.
    Last edited by jlm; 3rd July 2011 at 13:14.

  16. #116
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    Re: Tech cameras and IQ.

    John,

    My apologies for having misread your name: it must be my eyes, getting older, it definitively is. But with time passing I will certainly become aquainted with all these name particularities.



    As for what is written concerning the helical focus ring:

    with the risk of being "attacked" from some and the argument going on, this is all theoretical and does not hold in the field. I stand by my point of view, but respect others if they believe so.

    But could Andreas Gursky, Walter Niedermayr, Mark Dubovoy, Candida Hoefer, Raymond Depardon, Ardon Bar Hama, Raymond Meier, among many other top-photographers all be that wrong when they choose Alpa because it gave them the most precision in focusing and fine-tuning among all cameras available?

    With all due respect for anyone here, and theoretical precision and literature put aside, it's the practical use and the resulting images which speak for themselves, nothing else. All the rest is only endless discussions or arguments making no sense in the field and when it comes to the point, showing an image.

    This is not to speak bad in any way about Arca or those working with this camera. To each one his respected choice. But pretending like it is done in this thread and some others that all of a sudden Arca is the non-plus-ultra in focus precision is going a little too far and not the truth. There still is a difference between the theory and the practice.

    More about it, with some relevant information, tomorrow. Going to have a sleep now.

    Best regards
    Thierry

    Quote Originally Posted by jlm View Post
    jack: i kind of like the ambiguity all those verticals give in my name.

  17. #117
    Sr. Administrator Jack's Avatar
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    Re: Tech cameras and IQ.

    Quote Originally Posted by TH_Alpa View Post

    But could Andreas Gursky, Walter Niedermayr, Mark Dubovoy, Candida Hoefer, Raymond Depardon, Ardon Bar Hama, Raymond Meier, among many other top-photographers all be that wrong when they choose Alpa because it gave them the most precision in focusing and fine-tuning among all cameras available?
    Did they test for precision directly against Arca? If so, I'd like to hear from them exactly how they found Alpa "superior." Or is more accurate that they just found that the Alpa was "sufficient" for their needs? In this case, I have no argument. I know Mark Dubovoy was not happy at all until he shimmed.

    With all due respect for anyone here, and theoretical precision and literature put aside, it's the practical use and the resulting images which speak for themselves, nothing else.
    Agreed in that whatever works best for an individual is what they should choose.

    But pretending like it is done in this thread and some others that all of a sudden Arca is the non-plus-ultra in focus precision is going a little too far and not the truth.
    Please then define what you mean by "precision" for us Thierry. The Arca by any *mechanical definition* is more precise, period. You may have a different definition which I'd like to hear. Finally, you keep saying it is irrelevant in use, and that may be true for some folks, but that is a different discussion and does not change that fact that by a true mechanical definition, the Arca helical is more precise than the Alpa's. Just trying to keep the facts correct here .
    Jack
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  18. #118
    Senior Member Thierry's Avatar
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    Re: Tech cameras and IQ.

    Dear Jack,

    Shimming is another issue which needs to be explained as well: I shall come back to this later, tomorrow or another day with some input on this particular point.

    As for the rest, I shall as well come back to it, but not today, ways too late here, and I need to go and visit my bed.

    But I agree with you, words on paper and "mechanical definition" are facts, but unfortunately not all variables are taken in account in it.

    More later. Good evening
    Thierry

    Quote Originally Posted by Jack Flesher View Post
    I know Mark Dubovoy was not happy at all until he shimmed.
    Please then define what you mean by "precision" for us Thierry. The Arca by any *mechanical definition* is more precise, period. You may have a different definition which I'd like to hear. Finally, you keep saying it is irrelevant in use, and that may be true for some folks, but that is a different discussion and does not change that fact that by a true mechanical definition, the Arca helical is more precise than the Alpa's. Just trying to keep the facts correct here .

  19. #119
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    Re: Tech cameras and IQ.

    Without sounding rude, this thread is starting to turn into an Alpa sales pitch.

    As for dropping in the photographers names into the mix I'm sure if we had a direct representative from Arca on this forum they could list established photographers who have pledged their reputation on Arca's precision.

    Alpa or Arca, both are great camera manufacturers that offer precision equipment.

  20. #120
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    Re: Tech cameras and IQ.

    Wow. Thierry didn't make it through a week....

    I guess Doug Peterson's high post/negative comment ratio is really admirable.

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    Re: Tech cameras and IQ.

    Okay, I have to ask. Can someone give an example of a situation in which the Arca focus precision allows a user to do something that can't be done with an ALPA or Cambo?

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    Re: Tech cameras and IQ.

    In theory yes. A very fine focus stack for example but in reality this thread is starting to sound like because the Arca has a finer focus system it renders the Alpa/Cambo system inferior. I don't think for the average landscape shooter the differences really matter that much as looking at the standard of work shown on here, both focus methods are proven to work extremely well.

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    Re: Tech cameras and IQ.

    Quote Originally Posted by gazwas View Post
    Without sounding rude, this thread is starting to turn into an Alpa sales pitch.

    As for dropping in the photographers names into the mix I'm sure if we had a direct representative from Arca on this forum they could list established photographers who have pledged their reputation on Arca's precision.

    Alpa or Arca, both are great camera manufacturers that offer precision equipment.
    Agree and it's not what we want our commercial vendors doing. In Another words I had enough. Hope my point comes across very clearly here. Thanks Guy
    Photography is all about experimentation and without it you will never learn art.

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  24. #124
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    Re: Tech cameras and IQ.

    I've been a very proud Cambo shooter now for several years and have never felt I was using an inferior product thus have stayed away from commenting.

    Jack summed it correctly "Agreed in that whatever works best for the individual is what they should choose." Using a tech camera of any manufacture requires precision; some companies are offering slightly better precision than others. I've seen a lot of the added gizmos (my term) that are added to the camera to aid the shooter sometimes to the determent of the art (art of using a tech camera).

    Regarding which focus is best I submit that the photographer needs to know his/her equipment which can only be done by full hands on testing by themselves. I personally have never had a lens fail me. I on the other hand have failed the lens by not following a strict workflow pattern.

    As many of you know I recently upgraded to a P65. I mention that as before I saw flecks in the sky as I shot landscape. Those flecks have turned out to be birds. This impresses the hell out me for multiple reasons; the quality of the lens and resolution, as well as the resolution of the P65.

    The original question that started all this discussion was "...comparison (IQ) between a tech camera setup and a MF DSLR...".

    If you were shooting with the same digital back and the only difference was the tech camera with lens vs. a MF DSLR then I'd answer the IQ will be better with the tech camera. I saw this myself shortly after getting the Cambo and before I sold my Phase 645 and all the lenses.

    Just my 2¢ here...

    Don

    Guy - just saw your post after I posted mine...hope I don't offend.
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    Re: Tech cameras and IQ.

    Quote Originally Posted by stephengilbert View Post
    Okay, I have to ask. Can someone give an example of a situation in which the Arca focus precision allows a user to do something that can't be done with an ALPA or Cambo?
    Stephen, I don't know if this qualifies. When I got my IQ180 I was trying to work out focus on my 43xl. So, I went to the marina where I had lots of things at all different distances and wanted to see what was going on. A few things to note. This was a focus test so I didn't bother correcting all files with an LCC. I also think as others do that you can get good results with all of the systems. The question becomes how easily and what is the best work practice for the person. I just know for me the Arca gives me a lot of precision when focusing. I did the same test at a distance of 3 feet and that means very large movements on the helical for a huge leeway for fine tuning.

    Here are the two things in my opinion where I think Arca works well. I don't have enough experience with other systems to make any categorical statements. Here is the original shot.




    I took a whole series of shots at 0, 1, 2, 3, 4, 5 on the focus helical. Please note each of those would be a big increment and I have a lot of room to fine tune between these numbers (go back to Jack's post and math). the first two crops on the left look pretty close and they are full number apart. As I came to see what I was getting I then moved in to test in smaller increments like 1,1.4,1.8, 2.2 I just don't have all those files easy to line up right now.

    So here are the differences in a screen shot of the overlayed exposures



    So, my two take aways from the Arca system is the way it focuses I get good focus without shimming the back and secondly there is a lot of room to fine tune the focus.
    Last edited by Terry; 3rd July 2011 at 16:42.

  26. #126
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    Re: Tech cameras and IQ.

    If one takes a look at the back of a Phase back, one might notice four shiny spots.
    Those spots are lapped, meaning they are ground flat and are designed to be what establishes the reference from the sensor plane for distance and parallelism.
    Precise cameras that attach that back ought to have four similar spots, also lapped, arranged to contact the corresponding points on the back. If that has been done well, the back and camera are "zeroed in" and sensor will be at a known reference in parallelism to the lens board and at known distance from the helical.
    Some vendors provide shims to adjust these points either because they have not lapped them to the necessary degree of precision or because they have found that their is enough variation in their bodies to warrant this.
    That is totally ok, but others might not need this adjustment, or might use another mechanism for adjusting the distance such as an arbitrarily numbered scale on the helical.
    The ONLY potential advantage to the shimming approach is that it allows for a greater degree of manufacturing variation in the camera body so that it can be brought into tolerance with shims. Of course along with shims comes the variation that various pressures will have on the thickness of a pile of shims given oil coatings, flatness, and so forth.
    There are plenty of ways that a body may be built, but castings are generally less precise than bodies that are machined out of bar metal unless they have had thei critical dimension machined.

    Bottom line is that I can trust or adjust a body to suit my needs, so the remaining distinguishing characteristics of Tech cameras (besides movements, lets not discuss them at the moment) is the helical or other focusing mechanism and the quality of the lenses themselves.
    -bob

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    Re: Tech cameras and IQ.

    Not at all Don.

    Here is my take . Btw I have not bought a tech cam YET but I have used all three systems and some nice gear for sure and in general very precise tools . But let's face it easier to focus no question a MF DSLR pick your brand it's easier than a tech cam period. Now precisely if you look at our olderanual focus lenses from our 35mm days . Any lens compared to any other lens with the same focal length the longer the focus the more precise you can get the focus easier and fine tune better. Nothing changed here with tech cams or even view camera the more travel you have the better nailing the focus. This is just logic. Same rules apply with a tech cam. Think a 85mm canon 1.2 with the long focus compared to a canon 85 1.8 with a shorter throw. The 1.2 you can achieve a more critical focus
    Photography is all about experimentation and without it you will never learn art.

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    Re: Tech cameras and IQ.

    Damn iPhone
    Photography is all about experimentation and without it you will never learn art.

    www.guymancusophotography.com

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    Re: Tech cameras and IQ.

    Quote Originally Posted by Guy Mancuso View Post
    Not at all Don.

    Here is my take . Btw I have not bought a tech cam YET but I have used all three systems and some nice gear for sure and in general very precise tools . But let's face it easier to focus no question a MF DSLR pick your brand it's easier than a tech cam period. Now precisely if you look at our olderanual focus lenses from our 35mm days . Any lens compared to any other lens with the same focal length the longer the focus the more precise you can get the focus easier and fine tune better. Nothing changed here with tech cams or even view camera the more travel you have the better nailing the focus. This is just logic. Same rules apply with a tech cam. Think a 85mm canon 1.2 with the long focus compared to a canon 85 1.8 with a shorter throw. The 1.2 you can achieve a more critical focus
    Guy,
    Let's not confuse precision with accuracy or repeatability.
    If i were to take say an arca or an alpa I am much more able to set up a precise and repeatable focusing distance than is possible with the DF or the cambo assuming that the temperature were reasonably constant.
    The tech camera shooter might have this very repeatable setting but might have no real idea of the actual distance that it might correspond to. That is one reason that testing and calibration shots are needed.
    The DF on the other hand, might give you a fair degree of average accuracy with not a whole lot of precision or repeatability.
    Photographers for ages have used DOF to "cover up" this focusing ambiguity.
    with COC shrinking from the traditional .003mm to twice pixel pitch (or maybe sqrt(2) times pixel pitch have effectively crushed this tolerence down and sought improved degrees of both precision and accuracy.
    -bob

  30. #130
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    Re: Tech cameras and IQ.

    Totally agree Guy. The differences between a MF DSLR and Tech was brought home (again) while Ken & I were shooting almost side by side in the slot canyons. The difficulty of precise focusing on a tech camera (any tech camera) is part of the reason using one is such a slow process. However - the image quality of an image taken with a tech camera done right will blow your socks off.

    Here's a sample of a 2-image focal stack from last week. While the end result is somewhat pleasing if I had to do it over again I would have added a 3. Whether 2 or 3 it would have been the same. I use a Leica D5 for precision measuring then transferring the measurements onto the lens I set the focal point accordingly. I've done similar without the aid of a laser by guessing the distance and shooting 4.

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  31. #131
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    Re: Tech cameras and IQ.

    Quote Originally Posted by Bob View Post
    Guy,
    That is one reason that testing and calibration shots are needed.

    -bob
    So very very true!
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    Re: Tech cameras and IQ.

    Bob I kind of said that wrong to be honest and was going to delete it. I just cant get a iPhone to work like I think. LOL

    Drinking all day at a pool resort don't help either. LOL
    Photography is all about experimentation and without it you will never learn art.

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    Re: Tech cameras and IQ.

    Quote Originally Posted by Guy Mancuso View Post
    Bob I kind of said that wrong to be hOnest and was going to delete it. I just get a iPhone to work like I think. LOl
    That's okay just so long as you wern't driving and texting ....
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    Re: Tech cameras and IQ.

    Guy,
    Ah you have autospltvx activated
    -bob

  35. #135
    Administrator, Instructor Guy Mancuso's Avatar
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    Re: Tech cameras and IQ.

    Quote Originally Posted by Bob View Post
    Guy,
    Ah you have autospltvx activated
    -bob
    No just vodka induced. Lol

    Hold on!

    Hey bartender bring me another. ROTFLMAO
    Photography is all about experimentation and without it you will never learn art.

    www.guymancusophotography.com

  36. #136
    Sr. Administrator Jack's Avatar
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    Re: Tech cameras and IQ.

    Quote Originally Posted by stephengilbert View Post
    Okay, I have to ask. Can someone give an example of a situation in which the Arca focus precision allows a user to do something that can't be done with an ALPA or Cambo?
    Two areas for me Stephen: First is minor: allowing me to define a few different "infinity" focus points -- ie; 360 meters or 180 meters, or 90 meters. With the Arca I can hit these pretty precisely at f8, and while not impossible is going to be more difficult with a tradition tech helical. Will the differences be significant in a large print? Certainly not if you don't have the three versions to compare, but maybe yes if you do . Second and more significant for me, is when you impart tilts to alter PoF. Here minor changes in your focus point can have significant impact on how that PoF renders through the frame. This gets more critical as lenses get shorter.

    So my net is this: if you use tilt and especially with wide lenses, it can be a positive benefit to have finer control over your exact focus point.

    That's all my original point was. I will repeat for the 3rd (4th?) time that all of these systems are of great quality. I've used them all and all are capable of making outstanding images. Moreover I repeat that I believe shooters should use what benefits *their* working methods and styles first and foremost. And for me and *my uses*, I know the best option is the Arca for the reasons outlined earlier (tilt or swing with all lenses and both rise and fall movements at the back).

    Hope that clarifies,

    PS: And I agree with what Terry, Bob, Guy and Don are saying here -- we are all on the same page
    Jack
    home: www.getdpi.com

    "Perfection is not attainable. But if we chase perfection, we can catch excellence."

  37. #137
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    Re: Tech cameras and IQ.

    Don't worry we'll all be bored of sharpness and absolutely image quality soon enough and start wondering how we can pull and contort our gear ala Nick Brandts animal portraits, which, despite the innaccuracies of pulling the lens of a Pentax, is some of the most wonderful photography in history.

    On a serious note, I was wondering, after I have shimmed the Alpa max for one lens, are all lenses infinity stops really that accurate that the same shimming is fine for all lenses?

  38. #138
    Senior Member stephengilbert's Avatar
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    Re: Tech cameras and IQ.

    "I have shimmed the Alpa max for one lens, are all lenses infinity stops really that accurate that the same shimming is fine for all lenses?"

    That's what they say. According to ALPA, the shimming corrects for slight differences in the registry of the backs. But I wouldn't be surprised to hear some claim that the infinity stops can vary as well.

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    Re: Tech cameras and IQ.

    I just wanted to write a last part here. I personally think that both the Alpa and Arca are amazing products. When I made my decision a while back, I tried both cameras and it was a very close call. I am pretty sure that I could live with both cameras, for me the main point going with the Arca was the better lens shade system and tilt for ALL lenses.

    This does not make the Alpa a worse camera, it is still a fantastic system especially if one wants a tech and a walking around camera.

    That's all and I think I'm done in this thread.

  40. #140
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    Re: Tech cameras and IQ.

    It's not about the accuracy of the tool but how you use it.

    The Arca moves 2.5mm on one turn, divided by 172 marks. best we can do is probably half a mark which should move the lens .0073mm. For the Alpa this seems to be .017mm per half degree turn. Let's just assume the rest of the system doesn't degrade this precision.

    The following results are again for a 40mm lens at f/4. If we try to focus at 10m and have to live with the "inaccuracy" of the Alpa, we might be focusing anywhere between 9.51m and 10.55m. As I explained in a previous post, we should look at the range of maximum resolution. These would be 8.46-10.85m or 9.28-12.23m. This range increases rapidly at larger distances and 77m is hyperfocal for f/4 meaning maximum resolution from 38.5 and beyond. Focusing for 10pm at f/11 gives 7.37-15.56m. No need to worry about .5m more or less.

    Setting a 10m distance on the Alpa seems accurate enough for max resolution at 10m and we get some nice DoF front and back. Plenty of room for focus stacking too. At this distance your IQ180 can resolve objects of 1.3mm, while good eye vision resolves 4.0mm. So I am already taking pictures of details I can't possible see without binoculars.

    If you for some reason would like more control over the range of maximum resolution, please remember: a difference of 10 degrees Celsius (18 Fahrenheit) will cause 40mm bronze to expand/shrink .007mm. So whether you are using an Arca or an Alpa, do not forget to adjust for temperature unless your lens has any kind of temperature compensation which I doubt.

    Jack, focusing on 360m at f/8 gives you maximum resolution from 34.7pm and beyond. Focusing at 90m makes maximum resolution start at 26.9m. You should see no difference between the focus settings for any objects beyond 34.7m. Lens movement should be .0133mm. That is .9 mark on the Arca and .4 degrees on the Alpa. It might be easier to just warm up the lens 19 degrees. ;-)

    I for one believe the lovely rosewood handle on the Alpa is more important than the possible difference in accuracy. Accuracy is plenty on both camera's.

    Hans (still no geek)

  41. #141
    Administrator Bob's Avatar
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    Re: Tech cameras and IQ.

    The real challenge is owning all the bodies and all the lenses before you die.
    It is the variety that makes it so frustrating.
    -bob

  42. #142
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    Re: Tech cameras and IQ.

    Quote Originally Posted by Porpoise View Post
    It's not about the accuracy of the tool but how you use it.

    The Arca moves 2.5mm on one turn, divided by 172 marks. best we can do is probably half a mark which should move the lens .0073mm. For the Alpa this seems to be .017mm per half degree turn. Let's just assume the rest of the system doesn't degrade this precision.

    The following results are again for a 40mm lens at f/4. If we try to focus at 10m and have to live with the "inaccuracy" of the Alpa, we might be focusing anywhere between 9.51m and 10.55m. As I explained in a previous post, we should look at the range of maximum resolution. These would be 8.46-10.85m or 9.28-12.23m. This range increases rapidly at larger distances and 77m is hyperfocal for f/4 meaning maximum resolution from 38.5 and beyond. Focusing for 10pm at f/11 gives 7.37-15.56m. No need to worry about .5m more or less.

    Setting a 10m distance on the Alpa seems accurate enough for max resolution at 10m and we get some nice DoF front and back. Plenty of room for focus stacking too. At this distance your IQ180 can resolve objects of 1.3mm, while good eye vision resolves 4.0mm. So I am already taking pictures of details I can't possible see without binoculars.

    If you for some reason would like more control over the range of maximum resolution, please remember: a difference of 10 degrees Celsius (18 Fahrenheit) will cause 40mm bronze to expand/shrink .007mm. So whether you are using an Arca or an Alpa, do not forget to adjust for temperature unless your lens has any kind of temperature compensation which I doubt.

    Jack, focusing on 360m at f/8 gives you maximum resolution from 34.7pm and beyond. Focusing at 90m makes maximum resolution start at 26.9m. You should see no difference between the focus settings for any objects beyond 34.7m. Lens movement should be .0133mm. That is .9 mark on the Arca and .4 degrees on the Alpa. It might be easier to just warm up the lens 19 degrees. ;-)

    I for one believe the lovely rosewood handle on the Alpa is more important than the possible difference in accuracy. Accuracy is plenty on both camera's.

    Hans (still no geek)
    Hans
    You liberate me from a tormenting anguish . Now I know , that I do not have to go to university again and learn how to accurately focus my beloved ALPA STC . BTW with rosewood handles .
    Thanks for that . I already had nightmares .


    Quote Originally Posted by Bob View Post
    The real challenge is owning all the bodies and all the lenses before you die.
    It is the variety that makes it so frustrating.
    -bob
    Bob

    Very good comment . Thats what I am trying to do and thats , why I have way toooooooo much gear .

    I do hope , that I at least can shoot one PERFECT image before I die .
    My wish includes all parts in the image chain . Perfect camera , perfect (shimmed) digital back , perfect shooter , perfect software , perfect printer and perfect paper .
    And then , if the ignorant observers of that image do not see that this is the perfect image , all efforts were a waste of lifetime .
    I always thought , photography is much easier .

    Keep on posting such good comments .
    Regards . Jürgen .
    -----------------------------------------------------------------------------------

  43. #143
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    Re: Tech cameras and IQ.

    Quote Originally Posted by jotloob View Post

    I do hope , that I at least can shoot one PERFECT image before I die .
    My wish includes all parts in the image chain . Perfect camera , perfect (shimmed) digital back , perfect shooter , perfect software , perfect printer and perfect paper .
    And then , if the ignorant observers of that image do not see that this is the perfect image , all efforts were a waste of lifetime .
    I always thought , photography is much easier .

    Keep on posting such good comments .
    Perfect comment.

  44. #144
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    Re: Tech cameras and IQ.

    my point in getting numerical was to try to bring a bit of reality to the very tiny micron sized dimensions that are being waved around.

    In practice, you set up your shot and then, microns be damned, estimate the distance to the part of the subject to be in focus. That step right there is the weakest link. For distances in the 3 Meter range (10'), you could easily be off by 200mm (8"). Using a laser range finder or better a tape measure, you might get that down to 50-75mm (2-3").
    Now here is where the Arca system is useful: you look up 3 meters in the chart and set the ring to that number. Similar with the Alpa, if you have the fine focus rings. With the Cambo, you interpolate between numbers marked on the ring. (For example, my 70mm Rode has marks at 2 and 3 and 5 meters, each spaced more or less a comfortable 15mm apart; my 120 Schneider has 2.9, 3.5, 4 and 4.5M about the same spacing, and my 43 has 2, 3 5 about 10mm apart) (It would be so useful and simple to do if Cambo added more intermediate marks!!!)

    But ultimately you really won't know if you got focus until you peep your shot, and this is what it all boils down to, and why the IQ is so appealing.

    The only exception i can see is whether or not your lens can move close enough to the sensor when at the inf stop to really hit infinity, and here a test and shimming has proven useful. Once off the infinity stop, the effect of shimming is inconsequential
    Last edited by jlm; 4th July 2011 at 06:22.

  45. #145
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    Re: Tech cameras and IQ.

    Quote Originally Posted by gazwas View Post
    Without sounding rude, this thread is starting to turn into an Alpa sales pitch.
    It is? Sorry, but that's not the way I see it - I thought there was lots of useful information flowing back and forth (albeit somewhat drowned out by the chest thumping on both sides).

  46. #146
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    Re: Tech cameras and IQ.

    Quote Originally Posted by Porpoise View Post

    I for one believe the lovely rosewood handle on the Alpa is more important
    I'll give you that one
    Jack
    home: www.getdpi.com

    "Perfection is not attainable. But if we chase perfection, we can catch excellence."

  47. #147
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    Re: Tech cameras and IQ.

    Quote Originally Posted by Jack Flesher View Post
    I'll give you that one
    I'm so glad I can only afford to follow this thread without actually buying any of the items discussed therein... I guess I'd end up sleeping under a bridge in no time. Still, keep it up!

  48. #148
    Administrator, Instructor Guy Mancuso's Avatar
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    Re: Tech cameras and IQ.

    Quote Originally Posted by nightfire View Post
    I'm so glad I can only afford to follow this thread without actually buying any of the items discussed therein... I guess I'd end up sleeping under a bridge in no time. Still, keep it up!
    I already have my spot but I can rent you some. Lol
    Photography is all about experimentation and without it you will never learn art.

    www.guymancusophotography.com

  49. #149
    Super Duper
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    Re: Tech cameras and IQ.

    With all the problems folks have focusing, are you sure it is the camera? Perhaps it is time to visit Pearl Vision Center...

    I am 47 and bought my first pair of read glasses this year. Very depressing. But my prints are sharper.

  50. #150
    Senior Member Thierry's Avatar
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    Re: Tech cameras and IQ.

    After long thoughts (and a good night) I came to the conclusion that I won't bring my arguments to this topic, to the contrary of what I promised yesterday.

    It seems that it heats up the place, which I didn't mean to cause with my posts.

    I was of the opinion, that I have been very calm, respectful and understanding, and wasn't expecting such frontal attacks, having not myself attacked anybody.

    I have tried to give full information concerning a topic which is way too important that it can boiled down to a few claims or numbers on paper without having the possibility to discuss it with all the variables in the hands.

    My intervention was neither a sales pitch for Alpa, nor meant to try convincing, but rather a contribution with the wish to bring all the critical information concerning focus to those who wish to be fully informed before making a decision, nothing more.

    Therefore my apologies if some have felt hurt.

    Best regards
    Thierry

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