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Author Topic: Focusing Arca F69 with Digital Back  (Read 8669 times)
Jae_Moon
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« on: June 06, 2006, 04:10:10 PM »
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I got Arca F69 Metric with H1 digital back adapter (from Arca) for P45.

Arca ground glass focusing screen came with fresnel lens already installed (Fresnel between GG and Lens and the smooth side of it facing the lens).

After many trials, I am finding out that it is not focusing properly when the fresnel lens is installed. It will focus properly when it is removed. That leads me to believe that the camera is focusing on the fresnel lens instead of on the ground glass. The position of the GG is fixed regardless of the presense of the fresnel lens since it is sitting on a sepatate ridge from the fresnel lens'.

I talked to a Arca repair center tech and he is looking into the matter.

Does anyone have experiences with view camera focusing with fresnel lens and GG combination and have any suggestions what is going on?

thanks,

Jae M
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Jae_Moon
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« Reply #1 on: June 06, 2006, 07:09:18 PM »
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It is possible I am misfocusing with a loupe when I see the fresnel lens pattern. I am getting better focus when the loupe was properly focused on the image rather than influenced by grooves.

Any helpful suggestions how to focus the GG/FL. Does anyone have experiences with Beattie or other Bright screens?
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Eric Zepeda
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« Reply #2 on: June 07, 2006, 06:00:22 PM »
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My Kapture Group stitching back had a Beattie screen, and yes, you get better results focusing on the scene as opposed to the grooves. They are tempting targets, but it will move your focus plane just enough to render the actual scene less than sharp. I also went to a higher strength loupe, 8X which helped. The Kapture back allows a Hassy finder to fit on, but critical focus is very difficult to achieve.
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Jae_Moon
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« Reply #3 on: June 20, 2006, 01:41:29 PM »
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Martin Vogt of Arca-Swiss emailed me after he read my comment about having difficulty of focusing Arca 6x9 on a DB with fresnel lens attached to the ground glass. It is really nice to know that some of the reputable manufacturers are paying attentions to what customers are saying about their products. Also, thank you, Michael, for providing us an invaluable venue.

I reported to him that I still have problems with fresnel lens. 6x9 focuses tack sharp on my P45 with H1 adaptor if I remove the fresnel lens and just focusing on ground glass. I believe that the interference from fresnel lens is introducing about a half mm error. Checking the accuracy of focus with a DB is a snap since I take shots tethered to a PC and look at the results in 100% almost instaneously.

I do not use the fresnel lens now (except for the composing the frame since it is difficult to see whole image without it) and am relying on the ground glass for focusing. I am currently using Schneider 90 mm Digitar (47 mm will be here Thursday) and 10x loupe from Schneider also.

I ordered a Beattie Screen, am hoping it will provide a brighter image without focusing error. Maybe, Mr. Vogt of Arca-Swill may have a solution.
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bob mccarthy
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« Reply #4 on: June 20, 2006, 02:56:36 PM »
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The screen can be adjusted to compensate for a fresnel, but I'm not sure I would go this route. Others are available.

I like the fresnel to be on the outside of the GG for this very reason. Is that an option with the A-S? My technika will allow me to fit one either way.

Beatties are made of plastic and I found mine to bow out of adjustment in time. It went away. I went back to a glass GG.

Best of the bunch is the wax filled GG. They may make a bosscreen for your unit.

Try http://www.stabitech.nl for the boss screen.

Maxwell also has a following  Contact Bill Maxwell <maxwellprecisionoptics@yahoo.com>

And Satinsnow  <www.satinsnowglass.com>

Bob
« Last Edit: June 20, 2006, 03:01:12 PM by bob mccarthy » Logged
Jae_Moon
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« Reply #5 on: June 20, 2006, 04:57:53 PM »
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Bob:

A-S 6x9 does not allow a fresnel lens mounted on the outside of GG. Now, I just place the fresnel on the GG when I compose the shots.

I knew about Bosscreen and contacted them for a price quote. It must be the World Cup, I haven't heard from them in two weeks.

I just checked the web site of Satinsnow and I will give them a call. It does not look like 'wax filled sandwitch glass.'

Is Maxwell a 'sandwitched glass?'

thanks,

Jae M
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bob mccarthy
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« Reply #6 on: June 20, 2006, 10:33:05 PM »
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Bob:

A-S 6x9 does not allow a fresnel lens mounted on the outside of GG. Now, I just place the fresnel on the GG when I compose the shots.

I knew about Bosscreen and contacted them for a price quote. It must be the World Cup, I haven't heard from them in two weeks.

I just checked the web site of Satinsnow and I will give them a call. It does not look like 'wax filled sandwitch glass.'

Is Maxwell a 'sandwitched glass?'

thanks,

Jae M
[a href=\"index.php?act=findpost&pid=68687\"][{POST_SNAPBACK}][/a]

The boss screen is the only wax filled screen. The others are fine grain screens with their own twist.

I would use the boss but for the fact that i live in a hot climate and the screen has problems with high heat. For a studio or cooler climate its not an issue.

The maxwell is equally respected and equally high priced.

The satin snow is a "better than factory" product but is not overly expensive. The guy must be "burning one" constantly as he tell folks the tobacco scent is part of the product and will quickly disappear. Many praise his screen. I'm using OEM Linhof but would concider any of the others.

Bob
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Gary Ferguson
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« Reply #7 on: June 23, 2006, 09:25:57 AM »
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I've not had good experiences with Beattie screens, years ago I had a Hasselblad C series with a Beattie and focus varied at different points on the screen, which suggested it was warped. I subsequently heard that their manufacturing process can introduce stresses which work themselves out over time, rippling the screen as they do so. Later I had a 4x5 which also came with a Beattie screen and again I could never achieve consistently reliable focus with it.

The Linhof standard screen and fresnel I use now on a 6x9 camera is okay, but no better than okay. I'd like to use a x8-x10 loupe for digital, but at anything over about x6 or x7 I'm just looking at the grain of the GG.

The best screen I've seen for digital back applications are the standard Acute-Matte screen and fresnel screens that ship with the Hasselblad Flex Body, bright right out into the corners and with very fine detail that stands up to almost any loupe enlargement. I guess the fact that the Hasselblad uses different fresnels for different degrees of tilt must explain some of their advantage, but I'd be a happy man if I could replicate that focusing and viewing experience with the Linhof!
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BJNY
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« Reply #8 on: June 23, 2006, 10:11:46 AM »
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Is this item the solution for you Gary?

http://www.bhphotovideo.com/bnh/controller...oughType=search
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Guillermo
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« Reply #9 on: June 23, 2006, 11:49:40 AM »
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BJNY, now that's an interesting idea!

I've got one of those, and a V system adaptor for the Linhof. I'm kicking myself that I never thought of putting the two together. Thanks for the tip, I'll let you know how I get on.
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BJNY
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« Reply #10 on: July 01, 2006, 07:30:56 AM »
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BJNY, now that's an interesting idea!

I've got one of those, and a V system adaptor for the Linhof. I'm kicking myself that I never thought of putting the two together. Thanks for the tip, I'll let you know how I get on.
[a href=\"index.php?act=findpost&pid=68989\"][{POST_SNAPBACK}][/a]


So Gary, what pluses (+) & minuses (-) do you have to report?
Is this suggestion working for you?

Billy
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Guillermo
dfconnors
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« Reply #11 on: August 07, 2006, 10:20:46 AM »
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BJNY, now that's an interesting idea!

I've got one of those, and a V system adaptor for the Linhof. I'm kicking myself that I never thought of putting the two together. Thanks for the tip, I'll let you know how I get on.
[a href=\"index.php?act=findpost&pid=68989\"][{POST_SNAPBACK}][/a]

Sorry to be so dense, but I've not owned Hassy gear until getting an Aptus 22 back and H1 adapter for my F-Metric 6x9. Can I get a Hassy gg that will mount into the H1 adapter for the Aptus and will provide me the ability to focus (unlike the gg + fresnel problem I now have) ?

thanks, in advance, for any info

DF Connors
www.dfconnors.com
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Gary Ferguson
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« Reply #12 on: August 07, 2006, 03:54:13 PM »
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I tried the Hasselblad V series focusing screen adapter with the Linhof M679 and they appear to work well together in that it gives that typical Acute Matte look of fine grain, snappy focusing, and brightness. However, I need to double check the precise focusing accuracy with a tethered set up and a critical subject like a ruler at an angle. I've mainly be using a Canon recently but I'm shooting some interiors in a fortnight's time with the Linhof so I'll try it again then.
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dfconnors
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« Reply #13 on: August 07, 2006, 05:01:25 PM »
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I got Arca F69 Metric with H1 digital back adapter (from Arca) for P45.

Arca ground glass focusing screen came with fresnel lens already installed (Fresnel between GG and Lens and the smooth side of it facing the lens).

After many trials, I am finding out that it is not focusing properly when the fresnel lens is installed. It will focus properly when it is removed. That leads me to believe that the camera is focusing on the fresnel lens instead of on the ground glass. The position of the GG is fixed regardless of the presense of the fresnel lens since it is sitting on a sepatate ridge from the fresnel lens'.

I talked to a Arca repair center tech and he is looking into the matter.

Does anyone have experiences with view camera focusing with fresnel lens and GG combination and have any suggestions what is going on?

thanks,

Jae M
[a href=\"index.php?act=findpost&pid=67561\"][{POST_SNAPBACK}][/a]

Hi, Jae:

A few questions about removing the Fresnel lens:

1 - did you have to add spacers to maintain the proper distance of the gg?

2 - which screw driver for the screws? they appear to be Phillips, but the holes are not tapered inward... special screw driver?

Thanks, in advance.

Don

www.dfconnors.com
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Jae_Moon
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« Reply #14 on: August 20, 2006, 11:19:49 AM »
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Since encountering the 'focusing problem' with the factory installed 'fresnel + ground glass' with Arca 6x9, I have learned sevral lessons.  

I am using P45 with H1 adapter from Arca-Swiss, and do not use any sliding back. I have Schneider 35, 47, 90 and 210 mm Digitar lenses. Because I had an unfortunate P45 failure (a component in power supply) 5 weeks after I got my unit, I have had two P45s to test the focusing issues. I had a loaner from Phase One for 2 weeks.

1. Arca-Swiss (Martin Vogt) sent me an email to 'inform you that the Fresnel lens does change the focal plane by approx. 4/10. Nevertheless this is compensated on our ground glass.'

2. Arca-Swiss has focus error of .4 mm with fresnel lens installed in front of GG. The GG does not provide the compensation as Mr. Vogt indicates since the unit will focus perfect when fresnel lens is removed. However, the image is difficult to see without a fresnel lens. I have to use fresnel on opposit side for composing.

3. I tried Intense Screen from Beattie, and it is a $280 joke. It is a combination of 'fresnel and clear glass.' Image focuses on fresnel and the clear glass is for its protection. Fresnel sits on the same position as Arca's fresnel and the clear glass sit on the position where Arca's GG sits. First of all, the dimension of both fresnel and glass are wrong. Fresnel is way short and the clear glass requires rounding of all four corners to fit into Arca's GG frame.  I had to add a shim (just shy of 1 mm to raise the fresnel lens to focus properly). It is very grainy and the image is not evenly lit.

4. I contacted Boss Screen both in Holland and the US. As far as I can acertain, Boss screen is not in business. I have not received any reply from Holland. The US rep indicated same and he is contemplating producing the screen by himself sometime soon.

5. I ordered Satin Snow Ground Glass on June 20 and haven't received it yet. Mr. Parker of SSGG sent me an email that it will ship within a week on July 28 but I haven't got it yet. I am not screming because it was only $12 and I found the perfect solution, see below.

6. I ordered a focusing screen from Maxwell Precision Optics. It is a combination of 'fresnel/focusing matte screen and a clear protective glass. Both sit on the position where Arca's GG sit. The matte side faces the lens. IT FOCUSES TACK SHARP WITHOUT ANY FUSSES, NO SHIM, NOTHING. AND THE SCREEN IS VERY BRIGHT. It costs $225, and it includes the scoring of parallel lines for P45 image masking.

The focusing screen from Maxwell Precision Optics is  made with a slight convex warp on which a clear ptotective glass pushes down in order to maintain a perfect flatness in long tern exposure to different environmental conditions. Its micro prism frenel illuminates entire image so bright, even with 35 mm, I don't need to use a dark cloth to focus. The difference of brightness between the original Arca (if it focuses properly) and Maxwell is at least an order of a magnitude (obviously I don't know the exact difference since I do not have an instrument to measure).

I just returned from a two weeks trip to Peru, and have used all four lenses (35, 37, 90, 210) with perfect results. I did not have any problem with focusing and composing with Maxwell Precision Optics's focusing screen. By the way, the screen was ordered on June 29 and it was delievered on July 14.

Needless to say, Arca-Swiss 6x9  is a superb view camera. I don't know why the factory installed focusing screen does not function properly. But I can list several circumstantial evidences for anyone to make his/her own conclusion,

1. I used two separate P45s with identical results.
2. Arca's system will focus properly if I underfocus by 0.4 mm.
3. H1 adapter functions properly with Arca's GG only and Maxwell Precision Optics's screen.
4. All focusing tests were done by tethering the P45 to a PC and at 100% magnification.

Now, I am a happy owner of Arca Swiss 6x9 with Maxwell Precision Optics's focusing screen, Schnider Digitar lenses, and P45 DB.

Jae Moon
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Jae_Moon
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« Reply #15 on: August 20, 2006, 11:28:13 AM »
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Hi, Jae:

A few questions about removing the Fresnel lens:

1 - did you have to add spacers to maintain the proper distance of the gg?

2 - which screw driver for the screws? they appear to be Phillips, but the holes are not tapered inward... special screw driver?

Thanks, in advance.

Don

www.dfconnors.com
[a href=\"index.php?act=findpost&pid=72768\"][{POST_SNAPBACK}][/a]


Don:

Arca's focusing frame has two ridges; one for fresnel and the other for ground glass. Ground glass is not sitting on fresnel, so you don't need to add spacers.

I used a regular phillips screw driver, a small one. Since I had to change screens so many times to check the focus, screws (3) broke off and I had to drill them out.

As my previsou post, I strongly recommend Maxwell Precision Optics's focusing screen.

Jae Moon
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dfconnors
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« Reply #16 on: August 21, 2006, 04:58:33 AM »
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Don:

Arca's focusing frame has two ridges; one for fresnel and the other for ground glass. Ground glass is not sitting on fresnel, so you don't need to add spacers.

I used a regular phillips screw driver, a small one. Since I had to change screens so many times to check the focus, screws (3) broke off and I had to drill them out.

As my previsou post, I strongly recommend Maxwell Precision Optics's focusing screen.

Jae Moon
[a href=\"index.php?act=findpost&pid=73941\"][{POST_SNAPBACK}][/a]

Hi, Jae:

thanks for your reply. Perhaps I somehow got the gg into the ridges that hold the Fresnel, but focus was way off (behind object) after I removed the Fresnel. So I put it back in.  I'm using an Aptus 22 back with the H1 adapter marked "Phase One".

I got the "Live Video" dongle (thankfully, used) and will struggle through that arcane system to check focus. It does not allow stopping down to working aperture when in low light, so it is not terribly useful for me, but it may allow some insights into focusing.

Certainly, getting control over Scheimpflug movements has helped. I'm using the Rodenstock calculator with some good results. I roughly measured the micrometric detentes at 2.5 degrees each...

I will look into the Maxwell screen.

thanks again.

Don
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SatinSnow
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« Reply #17 on: August 24, 2006, 06:00:49 PM »
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5. I ordered Satin Snow Ground Glass on June 20 and haven't received it yet. Mr. Parker of SSGG sent me an email that it will ship within a week on July 28 but I haven't got it yet. I am not screming because it was only $12 and I found the perfect solution, see below.

Jae Moon
[a href=\"index.php?act=findpost&pid=73939\"][{POST_SNAPBACK}][/a]

Hi Jae,

Dave Parker here, Satin Snow Ground Glass,

I just wanted to post a note and verify that your screens had not arrived, they were mailed the week I said they would be and if they have not arrived by now, something has gone wrong in the mail system, which for some reason has happened on a few orders this summer, please let me know, as always, I am more than happy to ship a replacement order, if for some reason they don't show up..

Thanks, please let me know when you get a chance.

Dave Parker
Satin Snow Ground Glass..

PS..On another note, about the smoke smell, that was mentioned by someone, it does not embed in the glass, but does sometimes get in the packing materials, but we have never had a comment about the glass smelling like smoke, but again, yes, I am a smoker...
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Jae_Moon
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« Reply #18 on: August 24, 2006, 07:27:15 PM »
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Mr. Parker of SSGG emailed me with same question and offered me to send the replacement if I have not received the original shippment by mail. I informed him that I have not received the glass as of today, and he assured me that he will ship out the new one.

I am sorry that USPS failed me again. I am anxious to see how Satin Snow compare with the others.

Jae Moon
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Jae_Moon
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« Reply #19 on: August 30, 2006, 08:48:25 PM »
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Hi Jae,

Dave Parker here, Satin Snow Ground Glass,

I just wanted to post a note and verify that your screens had not arrived, they were mailed the week I said they would be and if they have not arrived by now, something has gone wrong in the mail system, which for some reason has happened on a few orders this summer, please let me know, as always, I am more than happy to ship a replacement order, if for some reason they don't show up..

Thanks, please let me know when you get a chance.

Dave Parker
Satin Snow Ground Glass..


[a href=\"index.php?act=findpost&pid=74389\"][{POST_SNAPBACK}][/a]


I got the replacement ground glass from Mr. Parket today. Thank you. I will see how it compares to the original glass from Arca-Swiss and will let all of you know.

Jae Moon
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