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jotloob
Subscriber Member
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 .
Bob :ROTFL:
Very good comment . Thats what I am trying to do and thats , why I have way toooooooo much gear . :ROTFL::ROTFL::ROTFL:
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 .
Terry
New member
Perfect comment.
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
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
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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).
:ROTFL: I'll give you that one
N
nightfire
Guest
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!:ROTFL: I'll give you that one
Guy Mancuso
Administrator, Instructor
I already have my spot but I can rent you some. LolI'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!
Thierry
New member
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
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
On the contrary, information about these things is invaluable form people in the know but it got a bit more than that yesterday (Sunday).
Info about the focusing on the Alpa is interesting but turning it into a mines more accurate than yours thread IMO isn't helpful to anyone. I would to hear your points Thierry.
Info is power and helps perspective buyers when reasearching these exotic cameras and lenses. Tit for tat squabbles don't.
Don Libby
Well-known member
Thierry
We need to keep an open and honest dialog going otherwise the information that is shared can become too one-sided. Your area of expertise is Alpa and the information shared by you is valuable thus should not be stopped. I neither felt your contribution as a sales pitch or an attempt to convince one is better than another.
A person considering leaping into the wonderful world of tech cameras needs as much information both pro and con of all systems and they get it from you when it comes to Alpa. Likewise hands-on experience is invaluable, what works what doesn't work, or the work a rounds that were found from hard experience. It irks me that we don't have the same level of openness (for a lack of another term) from other manufactures. Why isn't there a rep from Cambo? Or if there is how the heck did I miss the post?
In short (or as short as I can be) - please keep it up. The one thing that brought me here in the first place is the open, frank discussions.
Don
Thierry
New member
Thanks Gareth,
May I simply refer to the earlier posts claiming that as such a helical ring had to be more accurate than the Alpa-type of focusing (this is better than that), basing these claims only on some calculations and numbers, but not all calculations and numbers coming in the equation.
If I want to do my "job" correctly" (inform and give accurate information), and knowing the whole story (without wanting to be pretending, since I had to look for it as well) and that it isn't that simple and that true as it was/is presented, I have to intervene and try to clarify with complete information.
Therefore I answered that it was true in se (that the helical ring of a Arca camera was in theory more accurate), but far from taking in count all the parameters, which when they are (taken in count in the theory and in practice), make the whole story look completely different. And there are some few more parameters in addition to the sole precision of this ring.
One sometimes tends (me included) to look, analyze and conclude only with the provided information, which sometimes isn't presented in extenso, sometimes purposely and sometimes by lack of knowledge (me included). This lack of full information unfortunately sometimes costs a lot.
But all that isn't that important if the sole result is to hurt others in their beliefs. That I don't want.
Therefore we can close this particular chapter.
Best regards
Thierry
May I simply refer to the earlier posts claiming that as such a helical ring had to be more accurate than the Alpa-type of focusing (this is better than that), basing these claims only on some calculations and numbers, but not all calculations and numbers coming in the equation.
If I want to do my "job" correctly" (inform and give accurate information), and knowing the whole story (without wanting to be pretending, since I had to look for it as well) and that it isn't that simple and that true as it was/is presented, I have to intervene and try to clarify with complete information.
Therefore I answered that it was true in se (that the helical ring of a Arca camera was in theory more accurate), but far from taking in count all the parameters, which when they are (taken in count in the theory and in practice), make the whole story look completely different. And there are some few more parameters in addition to the sole precision of this ring.
One sometimes tends (me included) to look, analyze and conclude only with the provided information, which sometimes isn't presented in extenso, sometimes purposely and sometimes by lack of knowledge (me included). This lack of full information unfortunately sometimes costs a lot.
But all that isn't that important if the sole result is to hurt others in their beliefs. That I don't want.
Therefore we can close this particular chapter.
Best regards
Thierry
+1 (Don)
Good on Alpa for actually having a presence on forums like this. Even if the debate gets heated, at least there is a debate. Trying to hold a similar conversation with Arca, Cambo, Linhof, Sinar etc. would just leave you talking to yourself...which, unless you're as old as the hills, is never a good thing.
Good on Alpa for actually having a presence on forums like this. Even if the debate gets heated, at least there is a debate. Trying to hold a similar conversation with Arca, Cambo, Linhof, Sinar etc. would just leave you talking to yourself...which, unless you're as old as the hills, is never a good thing.
David Duffin
Member
Thierry
Your comments here have surely made interesting reading for us all.
Being the proud owner of both an Arca Rm2d and an Alpa STC, I agree with your point of view. Although I admire the conceptual simplicity of the Arca's helical ring, I find myself almost always reaching for the Alpa for a couple of reasons
(a) I find the STC with HPF rings to be quicker and easier to gain acceptable focus at a known distance. (This may no longer be the case when the Arca eModule surfaces.)
(b) the somewhat smaller size and weight of the STC and shape of its wood grip make it easier to get a secure hold and IMO more pleasant to work with. I can remove the camera from its case and mount it with no fear of dropping it. I must say here, though, that my trusted Arca dealer Walter Borchenko recently provided me with an optional grip extension which has made the Rm2d much easier to handle. Highly recommended.
(c) mounting a lens with the Alpa clamps is more definitive. I'm never quite sure that the degree of tightness of the screw mount of lenses on the Arca is the same as it was when I did the calibration. Paranoia, perhaps?
Your comments here have surely made interesting reading for us all.
Being the proud owner of both an Arca Rm2d and an Alpa STC, I agree with your point of view. Although I admire the conceptual simplicity of the Arca's helical ring, I find myself almost always reaching for the Alpa for a couple of reasons
(a) I find the STC with HPF rings to be quicker and easier to gain acceptable focus at a known distance. (This may no longer be the case when the Arca eModule surfaces.)
(b) the somewhat smaller size and weight of the STC and shape of its wood grip make it easier to get a secure hold and IMO more pleasant to work with. I can remove the camera from its case and mount it with no fear of dropping it. I must say here, though, that my trusted Arca dealer Walter Borchenko recently provided me with an optional grip extension which has made the Rm2d much easier to handle. Highly recommended.
(c) mounting a lens with the Alpa clamps is more definitive. I'm never quite sure that the degree of tightness of the screw mount of lenses on the Arca is the same as it was when I did the calibration. Paranoia, perhaps?
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Emails and postings are difficult to do as they are often misinterpreted. It is a dangerous business.
Thierry, I would hope that you would basically ignore any confrontational responses in the future as I hope to learn from you why I made such a great decision!
Though I've been following this thread closely, I have to admit that there are some aspects to the helical focus and the lens complexity of the Arca system that concern me. Firstly, when you tilt, having to turn the lens focus rings four entire turns to determine nearest and farthest points (which is what I do before I begin tilting) seems incredibly painful. With tilt, I am constantly adjusting both tilt and focus until the parts of the image I want in focus are; it's a combination of these two controls that provides what I want. Often I use them simultaneously, which with so many turns of the helical would be, to say the least, inhibiting. Sure, I could do a Schiemflug calc each time and set it accurately, I guess, with the helical focus and the tilt measurements, but I trust my eyes more than a calc. And each scene is different. Studio shooting is different, but for what I do (landscapes) no two are the same...
So for MY type of shooting, MY workflow (without an IQ back) I saw the helical focus as a negative, not a positive.
And IMO and from MY real world experience, much of this discussion is counting angels on the head of a pin. The MFDBs are outstanding; Phase, Leaf, Hasselblad/Imacon/Whomeverownsthemnow. And all of the tech cameras being bantered about here are going to give you results that will simply blow your shorts off.
So thanks to EVERYONE who contributes to the thread (I certainly learned a lot and have a lot of respect for all who go into such terrific detail in their testing). Think about these wonderful test results; think of how you shoot; think of what is REALLY important to your workflow. All important factors and all valid contributions to this great forum...
I'll go take my meds now...
Best,
Bob
Thierry, I would hope that you would basically ignore any confrontational responses in the future as I hope to learn from you why I made such a great decision!
Though I've been following this thread closely, I have to admit that there are some aspects to the helical focus and the lens complexity of the Arca system that concern me. Firstly, when you tilt, having to turn the lens focus rings four entire turns to determine nearest and farthest points (which is what I do before I begin tilting) seems incredibly painful. With tilt, I am constantly adjusting both tilt and focus until the parts of the image I want in focus are; it's a combination of these two controls that provides what I want. Often I use them simultaneously, which with so many turns of the helical would be, to say the least, inhibiting. Sure, I could do a Schiemflug calc each time and set it accurately, I guess, with the helical focus and the tilt measurements, but I trust my eyes more than a calc. And each scene is different. Studio shooting is different, but for what I do (landscapes) no two are the same...
So for MY type of shooting, MY workflow (without an IQ back) I saw the helical focus as a negative, not a positive.
And IMO and from MY real world experience, much of this discussion is counting angels on the head of a pin. The MFDBs are outstanding; Phase, Leaf, Hasselblad/Imacon/Whomeverownsthemnow. And all of the tech cameras being bantered about here are going to give you results that will simply blow your shorts off.
So thanks to EVERYONE who contributes to the thread (I certainly learned a lot and have a lot of respect for all who go into such terrific detail in their testing). Think about these wonderful test results; think of how you shoot; think of what is REALLY important to your workflow. All important factors and all valid contributions to this great forum...
I'll go take my meds now...
Best,
Bob
Question, what CoC did you use? I just had some time to pull my calculator out and by some loosey-goosy reverse analysis, it appears you used approximately 2-pixels or just over 10u as your CoC. And I'd agree that is a conservative CoC to choose even for super critical print purposes. However, if you use actual pixel view (CoC~=5.2u on teh IQ180/Aptus 12) to confirm precise infinity focus, I assure you you can "see" 90m, 180m and 360m pop into focus at different settings, and then have your 5Km infinity look a little "soft" at either the 90m or 180m focus point relative to the 360m focus point, again using f7 for a little more criticality than f8. Now I agree this difference may be academic, but with the IQ180 sensor, it is now VISIBLE, so IMHO it is worth discussing... In use and IMHO only, I think a realistic "infinity" for practical PRINT uses would be 90m with this 40 at f8 over the IQ180/Aptus 12 back.
Cheers,
Jack, could you explain the advantages of having 'different infinity focus point' for me? I am trying to learn the 'in and out' of technical/view camera focusing.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
Also, does Arca Rm3d have a 'calibrated tilt' dial so you can set to an exact angle (1.8 degree or 2.5 degree, etc) the same way focusing are done in micron?
Jae Moon
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P
Porpoise
Guest
An Epson 9900 started my spiral dive into digital MF territory. As PhaseOne asks .0615 dollar cent per pixel, I want full use of each and every pixel. So I always use the pixel size as CoC in the formula
Front DoF = CoC x Fstop x Distance^2 / ( FocalLength^2 + CoC x Fstop x Distance )
When focussing at 360m with a 40mm lens at f/8, at 90m you should get a CoC of .0019mm. Focusing at 90m you get a CoC of .0022mm at infinity. So the results seem quite consistent.
The formula I use, could be wrong, but I start to suspect the interaction between pixel size and CoC might be more subtle than we think, and perhaps CoC should be a lot less than pixel size, more like .002mm. That would explain what Jack is seeing, but makes me worry about diffraction. More experiments, perhaps with ABX-comparing, seem necessary. :-D