Ad
Ad
Ad
Pages: « 1 2 [3]   Bottom of Page
Print
Author Topic: Linhof Techno, can you really focus with it?  (Read 8998 times)
torger
Sr. Member
****
Offline Offline

Posts: 1286


« Reply #40 on: March 06, 2012, 09:39:21 AM »
ReplyReply

And in the case of a camera like the Techno, the important factor is the difference between the position of the ground glass vs. the sensor--that is what needs to be precise.

Yep, but the adapters are not shimmable, right? So if the sensor alignment or glass is off, game over, right? Or are you supposed to fix it with shimming tape, or give the dealer an angry call and send back your stuff, even if you got your back separately and you don't really know if it is the back, back adapter, ground glass adapter or ground glass that is off?

The only shimmable adapter I've seen so far is the ones from ALPA. With the price the adapter plates have I guess one could demand 10 um precision, but the sensor could be off too, and concerning digital back sensor alignment precision I've not heard the best.
Logged
darr
Full Member
***
Offline Offline

Posts: 109



WWW
« Reply #41 on: March 06, 2012, 10:27:49 AM »
ReplyReply

Yep, but the adapters are not shimmable, right? So if the sensor alignment or glass is off, game over, right? Or are you supposed to fix it with shimming tape, or give the dealer an angry call and send back your stuff, even if you got your back separately and you don't really know if it is the back, back adapter, ground glass adapter or ground glass that is off?

The only shimmable adapter I've seen so far is the ones from ALPA. With the price the adapter plates have I guess one could demand 10 um precision, but the sensor could be off too, and concerning digital back sensor alignment precision I've not heard the best.

A couple of solutions:
1) Shoot tethered
2) Test your lenses for the tweak
3) If sensor is off by a lot (warped?), send the digital back to the manufacturer for repair

A reason to purchase the best quality or wait for the prices to come down or shoot FF Nikon, Canon, etc.
« Last Edit: March 06, 2012, 10:29:52 AM by darr » Logged

torger
Sr. Member
****
Offline Offline

Posts: 1286


« Reply #42 on: March 06, 2012, 12:51:05 PM »
ReplyReply

I'm not sure if I'm right, but as far as I have understood the main reason why Alpa has shims in their back adapters is not to compensate for limitations in precision in their equipment, but for make up for issues with digital backs. I've also got the impression that it really does not matter which back you buy cheap or expensive, since no digital back manufacturer live up to their standards when it comes to sensor alignment.

I'm not even sure if I need to care about shimming. Would my eyes and fingers provide 10 um precision in bellows focusing? I would not think so.

But people do say things like "it is important that the ground glass and sensor plane is perfectly aligned", and then the natural follow-up questions are -- does misalignment occur often, and how large is the error? What do you do if they are not aligned (Linhof do not have any shims as far as I can see)? Say if it is off by 20 um, it probably does not matter to me. But if it is off by 100 um, then it may become relevant. But how likely is that? It may look like I'm in search for perfection, but really I'm not. I want to find out if problems that are discussed on the net are real (as seen from my horizon), and if real how to deal with them.

It could be the case that shimming is in practice only relevant for helical focusing systems, since for bellows focusing you're not dealing with that kind of precision in focus placement. I don't know.
« Last Edit: March 06, 2012, 12:54:01 PM by torger » Logged
darr
Full Member
***
Offline Offline

Posts: 109



WWW
« Reply #43 on: March 06, 2012, 12:59:42 PM »
ReplyReply

It might interest you to watch these videos on the before and after results of shimming an Alpa:

Part One-A
Part One-B
Part Two

BTW, I purchased my Alpa Max from Paul and highly recommend him. He is a very knowledgeable guy and excellent businessman. I stay with Alpa in part because of his business practices and commitment to his clients.

Also, I think you may be right about the shimming affecting helical mount lenses in particular. When I am focusing my ML2 in the studio with standard mount digitar lenses and tethered, I can see immediately where the focus plane is.
« Last Edit: March 06, 2012, 01:02:27 PM by darr » Logged

Geoffreyg
Sr. Member
****
Offline Offline

Posts: 406


WWW
« Reply #44 on: March 06, 2012, 01:15:50 PM »
ReplyReply

Shimming - Joseph Holmes makes a very convincing case. I ran across this issue with my Rollei Hy6 and some lenses that just didn't quite seem to have the pop I remembered. A friend with a similar setup was getting better results, and he recommended the focus adjustment that is in the camera.

Basically its an electronic shimming adjustment to compensate for what you and the camera think is in focus (with AF or Focus confirmation) with what is in true focus at the back. You dial in settings while fully tethered and live view, make a note, and then when you put that lens on, you simply dial up the adjustment.

Big surprise. Some lenses were right on, some were off. Make the adjustment and all are sharp. Reluctant before, am convinced now. Something from this is relevant to this thread - probably need to calibrate something in every digital setup with multiple pieces requiring  high precision but from different sources.  
Logged

Geoff
EricWHiss
Sr. Member
****
Offline Offline

Posts: 2307



WWW
« Reply #45 on: March 06, 2012, 01:51:50 PM »
ReplyReply

As far as I understand it, the shimming only adjusts the fore / aft spacing.  You rely on the high quality machine work from the different vendors for angular alignment with respect to the lens axis and also that the back will be actually centered when all movements are set to their zero detents.  If anyone knows of easy ways to check these last two positioning factors, I'd love to hear them. 
Logged

Authorized Rolleiflex Dealer:
Find product information, download user manuals, or purchase online - Rolleiflex USA
theguywitha645d
Sr. Member
****
Offline Offline

Posts: 970


« Reply #46 on: March 06, 2012, 06:49:43 PM »
ReplyReply

The Alpa shimming, from the demonstration, is just finding infinity focus for the back. But what you need to do is find if the ground glass and sensor are at the same position. The Alpa shimming is also only setting the infinity stop for a particular temperature and lens--you would need to confirm that all the mounts are the same. Now either the Alpa is going to be used with guestimatation focusing, which questions this technique as focus precision is going to be low, or you are going to use a ground glass, at which point then the only important thing would be the difference between the sensor and GG--shimming is neither here nor there.

BTW, I do not think a distance 20X the focal length in meters is really infinity. When I had a Mamiya 6 rangefinder lens calibrated for infinity with the body, Mamiya told me that the target had to be several kilometers away or the rangefinder will show something less.

As far as my Linhof sliding back, I have no problems focusing. The GG is where it needs to be for focus.
Logged
Geoffreyg
Sr. Member
****
Offline Offline

Posts: 406


WWW
« Reply #47 on: March 06, 2012, 07:55:50 PM »
ReplyReply

If you don't mind, are you using a Linhof sliding back, or Kapture Group?
Logged

Geoff
theguywitha645d
Sr. Member
****
Offline Offline

Posts: 970


« Reply #48 on: March 06, 2012, 08:10:47 PM »
ReplyReply

I am using the Linhof back.
Logged
torger
Sr. Member
****
Offline Offline

Posts: 1286


« Reply #49 on: April 14, 2012, 02:01:07 AM »
ReplyReply

So I finally got my own Linhof Techno.

I started with a simple Rodenstock 35mm Apo-Sironar Digital, I probably will change it to a Schneider 35mm XL, but both are non-retrofocus so they should have very similar look on the ground glass. I also have the Schneider 47mm XL.

The 35mm is probably one of the most difficult lens there is for this system (if not the most difficult), since the shorter focal lengths are retrofocus. I found it easier than I expected to focus it, I do not feel that I need finer gearing or finer grained GG. I'll do more detailed testing of this in the future though. I only had a 5x loupe, but I think a 10x will be perfect for critical focusing. There's no need to remove the fresnel for critical focusing either, that's great.

Anyway, while focus control was better than I expected, the dimness of the ground glass was worse than I expected. I have Linhof GG and fresnel, and a lighthood with magnifier.

It is about equally bad at 35 and 47mm. In an indoor scene when it is not extremely bright, one simply cannot see the whole scene at once. You see a bright spot where the light rays are coming dead on, so if you want to look around you have to move your head around to make the light rays fall straight in your eye. The fresnel improves it a little but not by much. With the light-hood and magnifyer on it is difficult to bend the hood enough to get the magnifyer in position so you can see into the corners.

Only seeing a small spot it may be hard to understand what you actually look at, but since you have your head in the direction of the light you just need to take a peek past the camera to see what the lens looks at in that direction. So it is indeed possible to compose images this way, but it is a bit cumbersome. It helps being a masochist. I expect it to be easier outdoors though, haven't had much time to test it yet. A focusing cloth makes a big difference too it seems.

The obvious solution to this problem would be to have a special wide-angle fresnel. Linhof actually have the fresnel separate, so it can be removed and another could be easily and quickly inserted. Problem is that Linhof only sells one generic fresnel, at least so it seems from the price list I have.

Any ideas?
« Last Edit: April 14, 2012, 03:59:58 AM by torger » Logged
IanB
Newbie
*
Offline Offline

Posts: 36


« Reply #50 on: April 14, 2012, 12:34:13 PM »
ReplyReply

I think the problem you are experiencing is generic with non-retrofocus wide field lenses on any view camera. It's the same with film - not exclusive to digital. Basically, you get used to it. As you say, it is much better outdoors.

One thing you may find helpful - I think it is possible to fit an Arca-Swiss binocular viewer on the back of one of these cameras. Using two eyes is better than one, and the tilt in the viewer means that you can move it to view the top and bottom of the screen image very well. Not so good for sideways shift, but it helps considerably nevertheless. Linhof make an adapter for this set-up for the Technikardan etc. (I use one for film work), so it I would not be surprised if the same is available for the M679/Techno back.

HTH
Logged
torger
Sr. Member
****
Offline Offline

Posts: 1286


« Reply #51 on: April 14, 2012, 01:12:51 PM »
ReplyReply

I think the problem you are experiencing is generic with non-retrofocus wide field lenses on any view camera. It's the same with film - not exclusive to digital. Basically, you get used to it. As you say, it is much better outdoors.

One thing you may find helpful - I think it is possible to fit an Arca-Swiss binocular viewer on the back of one of these cameras. Using two eyes is better than one, and the tilt in the viewer means that you can move it to view the top and bottom of the screen image very well. Not so good for sideways shift, but it helps considerably nevertheless. Linhof make an adapter for this set-up for the Technikardan etc. (I use one for film work), so it I would not be surprised if the same is available for the M679/Techno back.

HTH

Thanks for the tip, yes the arca binoviewer can be attached to the Techno with the help of an adapter. I tried detatching the magnifier from the lighthood and used some black cloth (actually a black t-shirt) to lengthen that lighthood over my face forming a light-tight funnel to look into, not like the binoviewer but $10 instead of $1000 :-), and it worked quite nicely. It is beyond me why Linhof has light-leaks in their own light-hood/magnifyer design (semi-open design so light falls in on the fresnel), but with the "funnel-focsing-cloth" I can stretch it over these openings too making it dark. I also find it a bit puzzling that they have easily exchangable fresnels but only one available to choose from. I imagine that a fresnel designed for the 35mm focal length would make it a bit brighter than the standard.

Overall my impression of the Techno is that the camera body is very well-designed, but the sliding back and viewing aids could be better.

Anyway, I suppose the 35mm for 36x48mm sensor should have the same issues as 90mm on 4x5" concerning the angle of light in the corners, so the image has only got smaller, but not darker.

I've played around in my dim appartment to really test the limits. I'll survive, but if there was such a thing as a custom fresnel or other solution that made it significantly brighter I'd probably go for it.
« Last Edit: April 14, 2012, 01:16:34 PM by torger » Logged
epines
Full Member
***
Offline Offline

Posts: 120


WWW
« Reply #52 on: April 14, 2012, 02:05:12 PM »
ReplyReply

Three things I've found to be a huge help when focusing indoors on a ground glass:

1. Bring a very bright flashlight with you. Place it near whatever you're trying to get sharp, and shine its spot on that area.

2. Place that flashlight next to what you're trying to have sharp, and shine it just to the side of the camera. Now focus on the bright flashlight head. Easy to see whether it's sharp or not.

3. Do the same thing with a laptop or iPad screen. Place it next to whatever you're trying to have sharp, maximize its brightness, and focus on the screen.

ethan
Logged

Christoph C. Feldhaim
Sr. Member
****
Offline Offline

Posts: 2508


There is no rule! No - wait ...


« Reply #53 on: April 14, 2012, 02:26:34 PM »
ReplyReply

focusing indoors with gg = use laser pointer
Logged

greygrad
Newbie
*
Offline Offline

Posts: 46


« Reply #54 on: April 14, 2012, 04:23:01 PM »
ReplyReply

The acute ground glass that Linhof recently discontinued for the Techno is superb - much, much brighter than the standard ground glass + fresnel. It's actually a Hasselblad Acute focussing screen in a custom Linhof holder. The holder also has slots for the Hasselblad RMFX finder which is very nice. It's so good I can't figure out why they discontinued it - perhaps there's something new on the way?

(Sorry for the small picture - the only one I could find on the net)
« Last Edit: April 14, 2012, 04:25:20 PM by greygrad » Logged
epines
Full Member
***
Offline Offline

Posts: 120


WWW
« Reply #55 on: April 14, 2012, 05:13:00 PM »
ReplyReply

focusing indoors with gg = use laser pointer

Can you elaborate?
Logged

torger
Sr. Member
****
Offline Offline

Posts: 1286


« Reply #56 on: April 15, 2012, 02:38:12 AM »
ReplyReply

Can you elaborate?

My guess is you point where you want to focus, so you get a red spot there and then you focus on that on the ground glass.
Logged
torger
Sr. Member
****
Offline Offline

Posts: 1286


« Reply #57 on: April 15, 2012, 02:44:11 AM »
ReplyReply

The acute ground glass that Linhof recently discontinued for the Techno is superb - much, much brighter than the standard ground glass + fresnel. It's actually a Hasselblad Acute focussing screen in a custom Linhof holder. The holder also has slots for the Hasselblad RMFX finder which is very nice. It's so good I can't figure out why they discontinued it - perhaps there's something new on the way?

(Sorry for the small picture - the only one I could find on the net)

Interesting! I've mailed with Bill Maxwell of "Maxwell Precision Optics" and he can do a ground glass too, he recommended his "HI-LUX Brilliant Matte 2.3" for my lens selection (35mm non-retrofocus, 47mm non-retrofocus). I may go for that but it will cost some due to a custom adapter is required, but still a lower cost than I expected.

I hope there's something new on the way from Linhof though, much of the criticism digital view cameras get is for the ground glass performance. If I were them I'd do my best to provide the best possible ground glass options.
« Last Edit: April 15, 2012, 03:48:24 AM by torger » Logged
Christoph C. Feldhaim
Sr. Member
****
Offline Offline

Posts: 2508


There is no rule! No - wait ...


« Reply #58 on: April 15, 2012, 01:50:21 PM »
ReplyReply

My guess is you point where you want to focus, so you get a red spot there and then you focus on that on the ground glass.

Exactly!
Logged

torger
Sr. Member
****
Offline Offline

Posts: 1286


« Reply #59 on: April 16, 2012, 02:07:29 PM »
ReplyReply

I actually heard a rumour just now from a Linhof dealer that Linhof is working on something concerning the ground glass, but it will probably be a few months still.
Logged
Pages: « 1 2 [3]   Top of Page
Print
Jump to:  

Ad
Ad
Ad