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IQ3 100 shimming question

tashley

Subscriber Member
SO please excuse my poor memory - it's been a while since I shimmed my IQ180 / Alpa STC combo.

I'm upgrading to the 3100 and so it seems to me that there's no need to shim it (or even, really, to remove the shim I already have in place) because the reason it was needed for the 180 was that there was no real possibility of focussing in magnified live view therefore I was using a Disto and an HPF ring on my Rodie - and they relied on the camera/back relationship being exact.

With the 3100 I can focus on the back in live view so I assume that the shim is redundant - so much so that I can probably leave the old one in unless it is stopping me reaching infinity.

Is that right, or am I missing something? Also, is there any point in taking the HPF ring off the Rodie 40 HR (if that can be done) to reduce bulk?
and complexity.

I guess I'll be retiring that Disto now, though it does have a surprising number of alternative uses!

Thanks in advance....
 

JeRuFo

Active member
That's right. If you only use live view, it's redundant because you are moving the whole lens back and forth while focussing, so it doesn't change anything optically either. For use with the HPF rings you needed to know that the sensor was placed at the exact distance from the lens, but as long as you can make the gap, you should be fine. It affects close focussing btw, since you are placing the sensor further from the lens.
 

dchew

Well-known member
SO please excuse my poor memory - it's been a while since I shimmed my IQ180 / Alpa STC combo.

I'm upgrading to the 3100 and so it seems to me that there's no need to shim it (or even, really, to remove the shim I already have in place) because the reason it was needed for the 180 was that there was no real possibility of focussing in magnified live view therefore I was using a Disto and an HPF ring on my Rodie - and they relied on the camera/back relationship being exact.

With the 3100 I can focus on the back in live view so I assume that the shim is redundant - so much so that I can probably leave the old one in unless it is stopping me reaching infinity.

Is that right, or am I missing something? Also, is there any point in taking the HPF ring off the Rodie 40 HR (if that can be done) to reduce bulk?
and complexity.

I guess I'll be retiring that Disto now, though it does have a surprising number of alternative uses!

Thanks in advance....
Tim,
I go back and forth with my opinion on this. On the one hand, LV theoretically eliminates the need. On the other, there is the infinity question plus the fact that if I test all my lenses, I still find the Disto/HPF combo to be the most accurate, although at normal f-stops not enough to matter. I still carry the disto in case it is really dark out.

Believe it or not, I went through and checked all my lenses. Not at infinity, but using Michael Tapes' Lens Align tool at various distances. 3 of 4 lenses were within 0.01mm shim. But one, my 90hrsw, was ~ 0.05 off from the others. Unfortunately it was close focusing compared to the others, which means if I shim to the others the 90 won't focus at infinity. So I actually shimmed to the 90 and offset my HPF rings on the other lenses. Again, in most cases it won't matter, but if I ever need to use the Disto, the HPF rings will be accurate on each lens.

Dave
 
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Ever since I switched to a CMOS digital back I removed shimming, and re-adjusted the HPF rings for each lens based on spot light from far away for infinity (because infinity is the only mark that matters to me).

When I have the time to do manual focusing I just use Live View. Occasionally when I don't have the time then I just use the HPF rings.
 

tashley

Subscriber Member
Tim

:ROTFL:

Oh boy are in for some expense after you see how well the IQ3100 performs.:grin:

I have discipline. In theory.

Because I have an STC with the Rodie 40HR, which I can use for pretty much all my landscape work, I have decided to go 'open box' on an XF body and 120 LS Macro blue ring. So that lens and body can cover my two other activities, being macro/still life (and with the excitement of automated stacking, yay!) and portrait in the studio. Mostly I'll be using the X1D for the portrait stuff though, I really like it in the studio because it's so light that you can dodge and weave.

Let's see how long this resolution lasts.... :ROTFL:
 

tashley

Subscriber Member
Tim,
I go back and forth with my opinion on this. On the one hand, LV theoretically eliminates the need. On the other, there is the infinity question plus the fact that if I test all my lenses, I still find the Disto/HPF combo to be the most accurate, although at normal f-stops not enough to matter. I still carry the disto in case it is really dark out.

Believe it or not, I went through and checked all my lenses. Not at infinity, but using Michael Tapes' Lens Align tool at various distances. 3 of 4 lenses were within 0.01mm shim. But one, my 90hrsw, was ~ 0.05 off from the others. Unfortunately it was close focusing compared to the others, which means if I shim to the others the 90 won't focus at infinity. So I actually shimmed to the 90 and offset my HPF rings on the other lenses. Again, in most cases it won't matter, but if I ever need to use the Disto, the HPF rings will be accurate on each lens.

Dave
that's a great point about when it's dark. Not generally in my shooting envelope but it could happen. So I might as well shim and keep the option open. I'll take a lazy start by seeing how it goes without re-shimming and I might get lucky....
 

f8orbust

Active member
Since shimming was always done to ensure accurate focusing at infinity, I don't see why it's less relevant on an IQ3100 than any other digital back.

Ideally you should have a separate (shimmed to match) back adapter per lens - rather than go for the 'one size fits all' approach - but at Alpa's prices, that could get real expensive real soon if you happen to have a few lenses ...

Jim
 

tashley

Subscriber Member
Since shimming was always done to ensure accurate focusing at infinity, I don't see why it's less relevant on an IQ3100 than any other digital back.

Ideally you should have a separate (shimmed to match) back adapter per lens - rather than go for the 'one size fits all' approach - but at Alpa's prices, that could get real expensive real soon if you happen to have a few lenses ...

Jim
I should shim the new back but since I nearly always shoot at around F11 on the Rodie 40, with LV focus at hyperfocal it probably won't ever make a difference. The novelty might be that I am so looking forward to good LV, but that the hyperfocal distance that is always set on my lens might actually be better...
 

tjv

Active member
Since shimming was always done to ensure accurate focusing at infinity, I don't see why it's less relevant on an IQ3100 than any other digital back.

Ideally you should have a separate (shimmed to match) back adapter per lens - rather than go for the 'one size fits all' approach - but at Alpa's prices, that could get real expensive real soon if you happen to have a few lenses ...

Jim
If Alpa are so serious about extreme accuracy and simplicity, would it not make more sense for them to implement a system where one can shim the lens mounts, instead of back adaptor plates? Or both in combination? What is the reasoning for doing back only, I wonder, if infinity differs on lenses and most people shoot with multiple lenses?
 

daf

Member
If Alpa are so serious about extreme accuracy and simplicity, would it not make more sense for them to implement a system where one can shim the lens mounts, instead of back adaptor plates? Or both in combination? What is the reasoning for doing back only, I wonder, if infinity differs on lenses and most people shoot with multiple lenses?
The good things with hpf ring, is that's so easy to adjust it for perfect focus/shimming...just unscrew it and focus to infinity using live view, turn the hpf ring to put infinity mark on the good position screw it back and you re done... it should take around 5minutes
 
The good things with hpf ring, is that's so easy to adjust it for perfect focus/shimming...just unscrew it and focus to infinity using live view, turn the hpf ring to put infinity mark on the good position screw it back and you re done... it should take around 5minutes
He probably means that he wants all lenses to have a hard-stop for infinity at the same time for the same digital back and camera body, so that he can shoot in the dark without illuminating his HPF ring. That would require shimming each lens individually.

Personally I find it not so necessary, as thermal expansion and contraction at different sites (e.g. from Africa to Greenland) can always offset any perfectly aligned HPF rings. I always tend to trust 100% zoomed Live View from a CMOS over HPF rings. It would be extremely rare to shoot a night scene where there is absolutely no light source for me to do a Live View focus with my lens wide open.
 

f8orbust

Active member

daf

Member
Another way to guarantee a hard-stop @ infinity for each lens without having to invest $$$ in multiple DB plates is to simply adjust the helical (not the HPF ring) on each lens. Thomas posted about it years ago ... was a bit tricky to find (most of the links to it no longer worked) ... but here it is, though sadly the accompanying images have long gone:

https://www.getdpi.com/forum/medium-format-systems-and-digital-backs/4730-fun-mf-images-92.html?highlight=#post240696

Jim
For sure it is better to adjust the helicoidal...
Regarding infinity stop, not sure that is a good idea : if one want to use tilt with creative use sometimes you need to go past infinity....
So probably best idea is to adjust the helicoidal to have some more range than infinity, and then adjust the hpf for perfect infinity indication...then you have a perfect set up ;)
 

GrahamWelland

Subscriber & Workshop Member
Agree on tilt and hard infinity settings. I've often had to focus past 'infinity' with tilt on my Alpa.

In my experience it's best to determine your own lens 'infinity' setting that ensures maximum forward DoF vs perfect at distance.

For Tim, since I've been shooting CMOS IQ150 & IQ3100 with Alpa and now Cambo Actus DB+, live view fixes everything so long as you can focus THROUGH infinity.
 

vjbelle

Well-known member
Since my purchase of the 3100 I have adjusted the shimming for my STC to go BEYOND infinity. All of the effort of making sure lens stops are accurate and infinity is really infinity is eliminated with live view on this back. All of this made more sense to me as I started to use my Actus with this back. I realize everyone has their preferences but this is mine and it works for me.

Victor
 
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