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Author Topic: Alpa question #2 - focusing  (Read 5217 times)

Michael H. Cothran

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Alpa question #2 - focusing
« on: December 26, 2011, 12:23:24 pm »

First, thanks to all who responded to my previous Alpa questions. Note - I have reviewed the Alpa site, so my concerns are things I could not find there.

Testing and shimming a specific digital back seems like the right thing to do on the surface. But, with the Alpa, the only time you know that the camera is in focus is when it is set to infinity. At any other focus point, it's an estimated crapshoot as to how accurately you are in focus.  Even with a laser pointer, it's still not that accurate, as the laser pointer would have to be set precisely where the digital sensor is, plus one would have to rely on the accuracy of the lens' markings, which, no matter how accurate they are, still cannot be accurately assessed between markings. So, at best, you are only in the ballpark. I suppose one could continually shoot, changing the focus slightly, and checking the LCD, until precise focusing occurs. But this is not always possible to do.

I've considered using the Alpa ground glass, but... 
1. Using ground glass means switching back & forth with the digital back. This opens up a big can of worms for keeping the sensor clean.
2. There's no mention on the website, so I presume the Alpa ground glass cannot be shimmed. So what good is it if you have a precisely shimmed DB? Focusing on the sensor and ground glass will most likely not match. Seems like being able to shim the ground glass to match the DB would be the best solution, but it's not an option, is it?
Furthermore, using the ground glass would enable one the see the effects of a polarizing filter. Something I use quite often.

I'd appreciate any comments, opinions, or tips on accurately focusing this camera. This seems to be my biggest concern.

FWIW - I shoot landscapes from a tripod only. For the past 40 years, I've owned and used a Hasselblad V system, most recently using a CFV 16 back. I'd like to upgrade, and the Alpa system appeals to me (other than the focusing ability). I've also considered using what I have, and purchasing a CFV50 back. I would like the shifting/stitching capabilities of the Alpa, not to mention the inherent IQ available.
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dchew

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Re: Alpa question #2 - focusing
« Reply #1 on: December 26, 2011, 02:15:15 pm »

Michael,
So, at best, you are only in the ballpark.

I don't think that's an accurate assessment.  Take for example the HPF rings on an HR-70mm, a middle of the road focal length.  At a typical focus distance of 10 feet, the markings (in ft) around that are: 9.99, 10.2, 10.4.  More like a few blades of grass in the ballpark.

I suppose one could continually shoot, changing the focus slightly, and checking the LCD, until precise focusing occurs. But this is not always possible to do.

If you have time to take off the back, put on the ground glass, struggle focusing on the dim 645 ground glass, take the glass off and put the back on, I would think you would have time for some minor focus bracketing.  It is not nearly as elegant, but I bet most would find it much more efficient!  Technical cameras make shifting so easy that even focus bracketing with shifts in between is not too bad.  If your subject requires precise focusing quickly, then as you already know, a technical camera is not the right tool.

I think with the small DB formats, it is really tough to focus on the ground glass more accurately than with the HPF/Disto combination.  Although I admit only trying it a few times.  Gareth may have a different opinion and certainly has a wealth of GG experience.

Regarding the polarizing filter, I agree it is a bit of a pain, and the IQ live view doesn't help with this.  I look through the filter, twist it to the effect I want, and look at the "clock" position of writing on the filter bezel.  Then screw it on and rotate it to the same position. 

Dave
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dchew

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Re: Alpa question #2 - focusing
« Reply #2 on: December 26, 2011, 02:36:07 pm »

Also don't forget focus mask on the IQ backs as a focusing aid.  For me that is at least as valuable as the live view feature.

Of course nothing is as good as "real" CMOS live view.

Dave
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vjbelle

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Re: Alpa question #2 - focusing
« Reply #3 on: December 26, 2011, 03:34:37 pm »

Your concerns are all very relevant but given enough time you will actually talk your way out of an Alpa purchase.  Once it is adjusted and you've learned how to focus quickly and accurately you will never regret your purchase.  I say this about the Alpa but it also applies to the Arca and Cambo..... all of these systems are capable of taking extreme high quality images.

Shimming, to me, is not a very accurate way of adjusting the Alpa lenses.  Yes, it will be accurate for ONE lens but not necessarily for others.  The best way for insuring a completely accurate system is to adjust each lens for infinity.  This really does take some time but then all lenses will match each other.  Its also very important to understand that you cannot adjust the Linhof helicoid lenses which includes any Schneider lens beyond 100mm.  I set my 150mm lens for infinity with the shimming method and then adjust all other lenses by adjusting the infinity stop which also affects all distances.  I am currently shooting with a 35mm, 60mm, 100mm, and 150.  There's no sense getting into how to adjust the lenses since you don't own any but it is a relatively easy process. 

Once you have infinity in focus you will find that focusing for other distances is really very easy and accurate whether or not you are using the HPF rings.  You also must realize that these lenses are shot at maybe f8.33 to f16. I don't usually shoot at anything less than f11 and rarely use f16. 

I would also never consider upgrading the V system.  The lenses aren't up to par and the whole system is just simply antiquated...... just my opinion.  You will never regret purchasing an STC....  its a dream of a camera and very easy to use.  A good dealer is very important.....

Good luck with you quest.....

Victor
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TH_Alpa

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Re: Alpa question #2 - focusing
« Reply #4 on: December 27, 2011, 01:30:38 pm »

hi Victor,

Just for the record and to correct something which could lead to misunderstandings: shimming a back IS NOT to adjust the lenses at infinity, never. In the contrary, shimming is done ONLY with a calibrated lens, which they all should be when purchased from Schneider or Rodenstock. I know that sometimes they aren't, but then it is up to the lens manufacturer to take the lens back and to do this adjustment, and it is not the Alpa shimming system which should "repair" such.
A shimming is done for the position of the sensor, ONLY.

Thanks and best regards
Thierry

Shimming, to me, is not a very accurate way of adjusting the Alpa lenses.  Yes, it will be accurate for ONE lens but not necessarily for others.  The best way for insuring a completely accurate system is to adjust each lens for infinity.  This really does take some time but then all lenses will match each other. ...  You will never regret purchasing an STC....  its a dream of a camera and very easy to use.  A good dealer is very important.....

Good luck with you quest.....

Victor
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michael

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Re: Alpa question #2 - focusing
« Reply #5 on: December 27, 2011, 01:48:13 pm »

Re the use of a laser rangefinder.....

The Leica laser is incredibly accurate; to within a fraction of an inch. With the HPS rings so is focus setting on the lens.

It is in fact more accurate than one can achieve using a groundglass which relies on ones eye's ability to decern accurate focus.

As for lining up the laser, it has a fold out reference arm which can be precisely aligned with the focal plane of the digital back. It takes about 10 second to place the laser beside the back, point at the subject, press the button, read the distance, and transfer it to the HPF ring. Nothing could be faster or more accurate.

Michael
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Paul2660

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Re: Alpa question #2 - focusing
« Reply #6 on: December 27, 2011, 04:36:12 pm »

Michael:

Which of the Lecia's are you using?  I am assuming it's one of the Distro lineup?   
Also with distances say over 30 yards in bright light, do you have any trouble seeing the red dot. 

If I understand the Distro lineup correctly , they don't use a optical viewfinder so you have to be able to see
the target dot on your subject. 

Thanks
Paul Caldwell


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Paul Caldwell
Little Rock, Arkansas U.S.
www.photosofarkansas.com

john milich

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Re: Alpa question #2 - focusing
« Reply #7 on: December 27, 2011, 06:50:29 pm »

disto 5 has an LCD screen with crosshairs showing what the dot is aimed at, it is zoomable as well
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dchew

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Re: Alpa question #2 - focusing
« Reply #8 on: December 27, 2011, 07:07:04 pm »

Yes, the D5 is the only very workable option for this application as far as I know.  Seeing the red dot works to about 10 or 20 meters.  Sometimes not even that far...

Dave
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richardhagen

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Re: Alpa question #2 - focusing
« Reply #9 on: December 28, 2011, 12:25:37 am »

the hilti PD 42 laser range meter has a built-in optical sight for measurements in daylight.

rh
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Graham Welland

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Re: Alpa question #2 - focusing
« Reply #10 on: December 28, 2011, 04:40:59 am »

I think that the OP is in danger of rather over thinking the whole technical camera focus approach and necessity for accuracy too. For most landscape shooting situations you don't need absolutely accurate focussing unless you are dialing in a foreground object which is most likely to be within distometer range. In most situations zone focussing works well enough at f/8 - f/11 around the primary focus point. Where you need greater DOF you can dial this in via approaches such as focus stacking or tilt depending upon what you are shooting with.

These days I find that I seldom use my distometer and actually the really fine accuracy of aligning with the sensor plane is only necessary if the focs point is pretty close in. I tend to use either estimation of distance, focusing with a manual lens on an RF or SLR and reading off the distance from the lens, use of a distometer (Leica D5) or for longer distances I'll use my Leupold RX-1000i rangefinder. In many cases though I don't need any aids beyond pretty decent distance estimation by eye.

As  mentioned earlier I think that there is a danger of convincing yourself that a technical camera can't possibly work and as we all know, this is definitely not the case! Five minutes shooting with a camera would put almost all of these concerns to rest. IMHO.
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Graham

TH_Alpa

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Re: Alpa question #2 - focusing
« Reply #11 on: December 28, 2011, 04:54:55 am »

As Graham says it, all this discussion makes it seem so complicated and bothersome, when it needs a few minutes of practice to get used to focus.

On a side note, Alpa has since 2009 specific information about which laser rangefinder to use:

Laser Rangefinder for the Alpa

Thierry
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vjbelle

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Re: Alpa question #2 - focusing
« Reply #12 on: December 28, 2011, 04:58:54 am »

[quote author=TH_Alpa link=topic=60624.msg488598#msg488598 date=1325010638
I know that sometimes they aren't, but then it is up to the lens manufacturer to take the lens back and to do this adjustment, and it is not the Alpa shimming system which should "repair" such.

Thanks and best regards
Thierry

[/quote]

More than sometimes, Thierry!! None of my lenses matched including replacements.  And, how is the end customer to know if a lens is correctly calibrated?  There really is no way of knowing if the infinity stop is set properly.  Alpa should take the time to test each lens before shipment......

Victor
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ced

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Re: Alpa question #2 - focusing
« Reply #13 on: December 29, 2011, 05:22:39 am »

I think just as Graham has pointed out in a very short time of using the Alpa for landscape you will see there is no real need to worry about focus as the be all and end all of taking photos unless you shoot all the takes at full aperture which for landscape you probably won't be doing.  Hyperfocal will meet most of your sharpness worries.
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BarbaraArmstrong

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Re: Alpa question #2 - focusing
« Reply #14 on: December 30, 2011, 02:33:12 pm »

This comment is triggered by Michael's posting about how easy it is to focus the Alpa.  Michael, you tantalized us with the promise of a future report on the STC after you'd had an opportunity to work with your new camera.  Have I missed something? --or how are things coming?  I, as doubtless many others on this site, am actively considering what my next camera should be. --Barbara
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michael

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Re: Alpa question #2 - focusing
« Reply #15 on: December 30, 2011, 09:01:17 pm »

Sorry Barbara, but other projects have gotten in the way.

Our latest addition to From Camera to Print does show using the STC plus IQ180 in a studio type environment.

Michael
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theguywitha645d

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Re: Alpa question #2 - focusing
« Reply #16 on: December 30, 2011, 09:37:40 pm »

When I was using a Horseman SW612, I would use an accessory rangefinder to focus the longer lenses--the wides were easy enough. You can pick up accessory rangefinders on ebay easily. Leica tends to be expensive. I liked my Ansco DeJur. Watameter and Waltz were good as well. Some rangefinders were metric and some imperial.

A Laser finder is a bit overkill.
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