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HansIt'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)
Bob :ROTFL: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
Perfect comment.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 .
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).Without sounding rude, this thread is starting to turn into an Alpa sales pitch.
:ROTFL: I'll give you that oneI for one believe the lovely rosewood handle on the Alpa is more important
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
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!
On the contrary, information about these things is invaluable form people in the know but it got a bit more than that yesterday (Sunday).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
ThierryAfter 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
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 buying when reasearching these exotic cameras and lenses. Tit for tat squabbles don't.
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.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.
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 .
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 formulaQuestion, 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,