Go Back   Rangefinderforum.com > Cameras / Gear / Photography > Gearhead Delights > Repair / Camera Care

Repair / Camera Care This is a good place to discuss the care and repair of your photo gear. You can share Do-It-Yourself repair and maintenance, as well as your recommendations for pro repairs. This new forum was created 4/1/07. PLEASE title your thread wisely, so others searching for a certain make of camera or repair person can find your thread easily!

Reply
 
Thread Tools Search this Thread Display Modes

Super Fujica 6 collimation
Old 08-01-2019   #1
johnnyrod
More cameras than shots
 
johnnyrod is offline
Join Date: Jul 2014
Location: Doncaster, UK
Posts: 411
Super Fujica 6 collimation

Can anyone help with this please? I've had the shutter out and I still can't figure out how you're meant to collimate it. The front element screws right in, it's unit focus. At about 7 feet the distance scale reads 6 feet (i.e. 7 feet from target to film plan and in focus). I tried adjusting the RF to match the lens and ignoring the scale, but it's not quite right across all distances. All I can think is to shim the whole shutter out until it's right, but that seems pretty crude. Thanks.
__________________
How does this thing work?
  Reply With Quote

Old 08-01-2019   #2
Sarcophilus Harrisii
Brett Rogers
 
Sarcophilus Harrisii is offline
Join Date: Jun 2009
Posts: 2,648
In the absence of any photos I had to try to google up some images of a Super Fujica Six. I like classic Fuji cameras but was not familiar with that model. Of course, I'd like one, now. Drat!

I'm at a major disadvantage not having ever handled one. But a couple of images I found show a unit focus lens shutter installation with focusing via a rotating ring at the rear. OK. This is all basic principles stuff—best I can do under the circumstances. And I can only presume the shutter is correctly installed in the lens standard with any original shims correctly situated, lens cells correctly fitted the right way around, etc. If not—all bets are off.

First off, forget all about the rangefinder for the time being. It's pointless adjusting it until the lens is correctly set (it is coupled to the lens, right?).

I wouldn't worry too much about the close range discrepancy either. Yes, of course, the distance scale ought to match the actual set focus distance of the lens up close, if not perfectly, then at least, pretty darned closely. And yes it's worth checking that later.

But the basic focus calibration of the lens will be done from the infinity stop. It's all about getting the sharpest possible infinity image. Once infinity is looking very good, (if the focus ring is not already at its infinity stop), dialling the focus in is all about rotating the focus scale ring to the stop without also moving the lens helicals as you do this.

This will have the effect of altering the relationship between the position of the ring, and the distance of lens to film plane.

Obviously, in order to be able to rotate the focus ring without taking the lens along for the ride—the key point, then, is to temporarily back off the fasteners that lock the helicals to the ring, so that the ring may indeed be moved independently of the lens focus.

It's at this point I can be of less help with specific advice on how the ring and lens are fixed to each other. In some designs, an external screw or screws may be visible somewhere on the circumference of the scale ring. These will fix the scale ring and focus grip to the lens unit so that rotating the ring also rotates the outer helical.

The images I have found don't show me the full 360 degrees of the scale ring. Not sure this applies for this model. There is one screw that fastens the thumb grip for the ring to the ring. This might, and I emphasise might just free the ring, so that, when you've got the infinity image looking sharp through the film plane, backing it off may permit you to rotate the ring to the stop before locking lens and ring together again.

If so, with infinity sharp, and the focus ring also on the infinity stop, all closer distances should then fall into place.

At this point doing a ground glass check against the distance scale isn't a bad idea. Why? (I've already told you that the lens is calibrated based on infinity, not close focus, right?).

Well, the infinity accuracy is how the adjustment is made. But Fuji are, like most well-known Japanese makers, a first quality lens manufacturer. If a comparison between the scale and tape measure reveals you still have a 30cm or so discrepancy at a few feet—better go back and revisit that infinity calibration. Chances are good that it's still not quite right. If it is, your close focus check ought to match pretty nicely.

A high powered loupe is essential to get really precise infinity calibration with a ground glass. I start off with a 8 x loupe, depending on the camera, lens, its maximum aperture and degree of brightness etc I may refer to a 15 x loupe as well.

Getting this adjustment spot on is not as easy as some tend to think. Getting the infinity looking pretty good is not so difficult. It's the final, almost imperceptible variations in target contrast that separate a calibration that's nearly right, from one that's spot on. And I suspect a lot of home DIYers don't have the patience (or practice) needed to achieve the latter, (or perhaps even to recognise they're not there, yet?). But once it really is right, the scale should typically agree with the ground glass within a centimetre or two (more or less depending on focal length and the resolution of the scale markings of course, some are much more rudimentary than others).

If you can't locate any external means of uniting the focus ring to the outer lens helical, you will need to remove the front lens cell and any trim covers that finish off the front of the shutter. You'll be looking for Eg screw heads around the outside of the shutter proper that may engage the focus array of the lens to the focus ring. Maybe even a circular plate or disc over the perimeter that contacts the end of the focus barrel. In this scenario, rather than rotating the focus ring to infinity to match the lens—you might pre-set the focus ring to the stop and, after backing off the fasteners, adjust the lens itself (with the front optics temporarily threaded on, of course) until the ground glass image is bang on. By tightening the fasteners without rotating the lens, lens and focus ring will thus be united at the correct infinity setting.

In the absence of a "T" setting on the shutter (does it have one?) a lockable cable release and the Bulb speed will make life that much easier as you inspect and fine tune the ground glass image.

Once you're confident the lens infinity calibration is accurate, you can dial in the rangefinder image to match (initially at infinity, but, as for the lens, cross checking the agreement between film plane and RF patch at five or six feet will inform you as to the accuracy of your infinity RF calibration).

Some systems feature more sophisticated "gain" or "rate of distance change" (aka linearity) compensation adjustments permitting you to perfectly match lens and RF at both close and distant ranges. These typically shouldn't need touching (if, indeed, they exist in the first place on the camera) unless it's been roughly treated, neglected or tampered with. If applicable, do not touch these in the first instance, and in any case, not unless you're absolutely certain it's warranted, else, you may chase your own tail trying to get agreement between RF and lens at all distances. Proceed on the basis that the accurately calibrated lens will match the RF at all distances when they match well at infinity, verify this up close, and simply revisit the RF patch at infinity until the close test is acceptable too, and you should be fine.
Cheers
Brett
  Reply With Quote

Old 08-01-2019   #3
B-9
Devin Bro
 
B-9's Avatar
 
B-9 is offline
Join Date: Jul 2009
Location: Michigan
Posts: 2,242
I have one sitting around,

Let me know if I can help!
__________________
Made in Michigan

RangefinderGuy @ Instagram
  Reply With Quote

Old 08-02-2019   #4
johnnyrod
More cameras than shots
 
johnnyrod is offline
Join Date: Jul 2014
Location: Doncaster, UK
Posts: 411
Hi Brett, thanks for the reply. Although I took the shutter out I didn't manage to take one of the covers off, it was a bit of a mystery how it all went together. There might be something under there. The focus helicoid has quite a lot of travel as you might expect, in other words at close range it has pushed the shutter a long way out from the standard, and you almost have to reset focus to infinity to close the door again. I'll have to investigate more, I was a bit wary of taking things off. The shutter leaves really want cleaning but I was unsure which 2 of the 3 screws I had to remove to get the escapement out, to then split the shutter, so had to settle for swabbing them instead. It looked a bit like the escapement was going to come apart, I don't want that job again. It's a Seikosha MX shutter and all speeds are close enough to warrant leaving it alone.

Regarding distances, I normally collimate at fairly short range such as 5ft/1.5m as it can be measured directly, and the small DoF means it's easier to get it right. The longer distances should line up as well, plus they have more natural DoF to sort out any inaccuracy. So far it's worked well. I use an SLR focus screen with a split circle, and I've made a holder that fits on the film plane so the front of the focus screen sits where the front of the film would be (negates the thickness of the holder).

I'm surprised how little info there is out there on this camera, in terms of using and repairing. It has auto film advance, which I can only presume works by loading the film and advancing to the pair of white arrows part way across the back, then closing the back and winding on. I can also only presume this will work fine with the thickness of Ilford FP4 today instead of 1955!
__________________
How does this thing work?
  Reply With Quote

Old 08-02-2019   #5
johnnyrod
More cameras than shots
 
johnnyrod is offline
Join Date: Jul 2014
Location: Doncaster, UK
Posts: 411
I'll do more investigation. For now I've uploaded the pics from the other day, not captioned them yet.
https://www.flickr.com/photos/bikegu...57710052909031
B-9 what can you tell me about film loading?
__________________
How does this thing work?
  Reply With Quote

Old 08-02-2019   #6
B-9
Devin Bro
 
B-9's Avatar
 
B-9 is offline
Join Date: Jul 2009
Location: Michigan
Posts: 2,242
The spools can be a bit tough to pinch out and into the back. Otherwise load as usual!

Have not had any frame spacing issues with mine. New and old stock film seem to track just fine.

Anything particular I can elaborate on with the loading? I can pull it out and load a dummy roll.
__________________
Made in Michigan

RangefinderGuy @ Instagram
  Reply With Quote

Old 08-02-2019   #7
johnnyrod
More cameras than shots
 
johnnyrod is offline
Join Date: Jul 2014
Location: Doncaster, UK
Posts: 411
Do you just line up the "start" line on the backing paper with the pair white arrows then close up and wind on to number 1?

I've made a video of about 3 minutes which might help understand the focus mechanism. There is a pin of about 4-5mm that locates the focus unit on the front standard. There is a small hole drilled in the front of the focus unit that locates a tiny screw head on the back of the shutter. Thus, the focus scale is in the right place on the standard, and the shutter body also lines up with the scale, so that when it's fully retracted, the focus scale shows infinity. The front two lens groups are turned in a single housing which screws in until it bottoms, equally the rear element screws in until it bottoms, so just like a Mamiya Six. There is a sleeve that screws onto the back of the shutter and attaches the shutter to the focus mechanism - this has to bottom as well otherwise they would rattle around i.e. it's not an adjuster. The error in the focus is about half of a helicoid thread, so it hasn't been put back in the wrong place,skipping a thread would throw it too far out the other way. The helicoid has two sliding screws to stop it just rotating, the ends of their travel correspond to shortest distance (about 4ft, on the focus scale) and infinity.
Anyway I am jiggered if I can figure out how to adjust this thing! Here's the video, it is uploading just now so give it half an hour or so from the time on this post if it isn't visible yet
https://youtu.be/B8sT8sfHVug
I would estimate a shim to correct the focus would be about 0.5mm thick, placed between the standard and the back of the shutter/focus assembly. It seems odd there appears to be no focus adjustment!
__________________
How does this thing work?
  Reply With Quote

Correctly Calibrating Film Plane & Viewfinder Focus
Old 08-03-2019   #8
Sarcophilus Harrisii
Brett Rogers
 
Sarcophilus Harrisii is offline
Join Date: Jun 2009
Posts: 2,648
Correctly Calibrating Film Plane & Viewfinder Focus

Quote:
Originally Posted by johnnyrod View Post
Hi Brett, thanks for the reply. Although I took the shutter out I didn't manage to take one of the covers off, it was a bit of a mystery how it all went together. There might be something under there. The focus helicoid has quite a lot of travel as you might expect, in other words at close range it has pushed the shutter a long way out from the standard, and you almost have to reset focus to infinity to close the door again. I'll have to investigate more, I was a bit wary of taking things off. The shutter leaves really want cleaning but I was unsure which 2 of the 3 screws I had to remove to get the escapement out, to then split the shutter, so had to settle for swabbing them instead. It looked a bit like the escapement was going to come apart, I don't want that job again. It's a Seikosha MX shutter and all speeds are close enough to warrant leaving it alone.

Regarding distances, I normally collimate at fairly short range such as 5ft/1.5m as it can be measured directly, and the small DoF means it's easier to get it right. The longer distances should line up as well, plus they have more natural DoF to sort out any inaccuracy. So far it's worked well. I use an SLR focus screen with a split circle, and I've made a holder that fits on the film plane so the front of the focus screen sits where the front of the film would be (negates the thickness of the holder).

I'm surprised how little info there is out there on this camera, in terms of using and repairing. It has auto film advance, which I can only presume works by loading the film and advancing to the pair of white arrows part way across the back, then closing the back and winding on. I can also only presume this will work fine with the thickness of Ilford FP4 today instead of 1955!
This is a very long read but I hope it's both clear, and helpful.

Correct Lens Calibration Procedures
I don't want to seem argumentative for the sake of it, but whilst you can certainly match lens focus and rangefinder together at a close distance, this won't ensure the infinity focus is optimised. Of course the lens and rangefinder ought to, hopefully, track together right out to far distances. But using the method you've described it's less likely that when the focus ring hits the infinity stop, it will be keyed at the precise point of sharpest infinity focus. If you're lucky it might. But it's more likely to either stop just short of infinity, or run just past it.

Yes, depth of field means you can potentially live with either of these scenarios because if RF and lens focus are always tracking together, what you "see" with the patch will be what you get on the film. But you don't have to live with a lens that is a little off in either direction at its maximum focus setting. Because by locking in the best possible infinity sharpness with the focus ring at its stop, you'll be avoiding any potential problems that might occur, if DOF can't mask the deviations between what the focus scale shows at infinity and where the lens focus actually is.

I acknowledge that in reality perhaps DOF will be ample enough that you might never notice, on your films, that the lens at its infinity stop is slightly out. The point, though, is that you can either run with that and hope it's of no consequence, or you can use best practice and set focus at infinity—in which case, it's a non issue.

In a perfect scenario (perfect distance scale, perfect alignments of your target plane at five feet and your film plane, perfectly measured five foot distance between the target and the film plane, etc) your system should see also see the lens focus fall in perfectly at infinity.

But, what if your measurements are slightly off, and five feet is really 4' 11 3/4"? Or if the planes of test target and film are slightly angled? Etc. At the infinity stop, you could be very close, but you may still be a bit off. Setting the focus at infinity, whilst a bit harder to nail, really is best. It's what the factory did, and it's what you should do, too. OK?

Calibrating a lens focus at infinity really well does get easier with practice and experience. I've been doing it for years and, depending on the camera and lens, how bright or dim the ground glass image is, and so on, I might spend a good half hour patiently fine tuning the lens image to get it spot on. I suspect the time needed is partly getting my eye acclimatised to the view through the glass, so that it can begin to spot differences in sharpness that are positively minute. Sometimes I can nail it in five minutes, but, various camera/lens combinations are easier to make miniscule adjustments to than others, so, it can often be easier to see the exact setting you want, than to get it, if your adjustment increments are too coarse (perhaps because of the friction, or other peculiarities of the method by which the lens focus is affixed to the focusing ring).

I'll labour the point here, because it might better clarify the scale of accuracy you're typically dealing with, if your goal is to obtain a level of focus calibration equal to what your camera maker originally achieved.

Here’s a photo of my usual target I use for infinity calibration. A dead gum tree on the ridge across the valley in which I live here in rural Tasmania. It’s nearly a kilometre distant as near as I can judge it. I’ve used few lenses, regardless of focal length, that don’t hit their infinity stop to get it sharp.




Here it is a bit closer.



I find the tree to be an excellent calibration target. Not just because of its distance. The main trunk, its offshoots and their subsidiary branches become smaller and smaller, and hence progressively harder to lock into clear focus from long range. Getting a sharp image of the trunk and its branches through a loupe and ground glass is typically a painless process. Once I can begin to differentiate the smallest twigs visible in the above image (taken with a cheap Fuji super zoom digital) by detecting a visible change in their sharpness, I’m well in the ballpark. It’s then a case of tweaking the focus back and forth in minute stages until its rests at the point those twigs are as sharp as I can differentiate. The next challenge will be maintaining that setting as you lock off the focus adjustment without disturbing it, often easier said than done.


Matching Film Plane Focus To Viewfinder Focus
I got onto this process when I was learning the fine art of repairing my first Rollei twin lens. I’d set the lens focus via the fixing collet nut around the focus shaft and focus knob. Once I had that as accurate as I could get it I’d then place a loupe inside the focus hood onto the top of the focus screen and repeat the process with the knob at the infinity stop until the ground glass image was at maximum sharpness. Off topic, but in the case of a Rollei the viewing lens being adjusted by backing off the securing screw or collar of the viewing lens to its threads in the lens board, and screwing it in or out independently of the focus knob, until sharpness at infinity is maximised (thus, locking viewing lens focus setting to that of the taking lens and assuring they would track together).

When I do a close focus cross check of my infinity settings to verify that the viewfinder matches the film plane, like you, I tend to set a contrasty target at about five feet. It’s close enough to absolute minimum distance to tolerate slight deviations at that minimum between the two (TLR) lenses, but far enough out that the infinity setting should see the lenses still locked in really well notwithstanding typical manufacturing tolerances of TLR lens matching, (or RF component precision, SLR mirror stop repeatability, etc.). On those rare occasions a factory manual might inform a specified distance for a close check you’ll most often find they will instruct this to be done not at the minimum focus stop of the lens, but at a range just a little longer than that.

I find that it is a good idea to do a blind test. What I mean by that is I’ll use my ground glass and loupe to set the sharpest possible image of the test target, but I won’t even look at the viewfinder, to see if it agrees with the ground glass focus. Despite one’s best intentions, it’s rather easy to see what you want to see. Yes, of course, you’ll notice gross discrepancies, but I’m talking about the most marginal of variations, here.

So, I’ll get the ground glass to maximum focus and then very carefully note the exact setting of the focus knob or ring. Maybe this will be against a number at the reference mark. It might be the alignment between one of the aperture markers and a numeral on the scale or knob. Point is, it will be a setting I can accurately note and then repeat as needed with extreme accuracy.

Only then will I check and adjust the viewfinder focus on the target for best sharpness. If subsequent inspection of the focus knob or ring reveals it’s exactly where it was set when the ground glass image was sharpest—it’s a pass. If separate tests of lens focus and finder focus give the precise same setting your infinity adjustments will be very good.

If they diverge slightly, the reason will usually be that your infinity check looked pretty good but was still just a bit off, and this does demonstrate that the distinction between an infinity image that is sharp, and one that’s absolutely bang on, can be extremely fine, indeed.

Originally the lens focus would have been optically calibrated by the manufacturer using auto-collimation, which makes the process both efficient and repeatable with a high degree of accuracy and consistency. Using a ground glass and loupes will take longer, but if you have a trained eye and the right aids can usually be just about as accurate, given a little patience.

Now, I mentioned this in the context of a TLR and its two lenses. But, it should be noted that it really doesn’t matter if you’re calibrating a SLR, TLR or a rangefinder. The schematics of the cameras may be very different, but the principle is exactly the same in every case. You’re setting the film plane infinity focus as perfectly as your eyes and equipment let you, then, dialling in the viewing system (whether that’s an SLR mirror and focus screen, TLR viewing lens and screen, or rangefinder focus patch of some sort) until the latter agrees with the former.

Split Wedge Focus Aid Considerations
May I also suggest that it’s safer to use a plain ground glass for calibrating lens focus than a screen with a split wedge aid? Whilst the latter are generally trustworthy, because they rely on the outer parts of the lens to work rather than the almost invariable better corrected centre, there can be instances when the split wedge won’t be as accurate as a plain ground glass. It’s true that a SLR made by a first quality manufacturer should, if its focus screen features a split wedge, almost always be reliable when it is used with the range of lenses the maker designed it for. Because you have been using a screen from a particular maker for calibrating other completely unrelated lenses, split wedge inaccuracy is a potential issue. I’m not saying it definitely exists with your set up—only that it’s possible. With a ground glass, it’s something you simply don’t need to worry about.

Herb Keppler wrote an interesting article about the little-known point of split wedge inconsistencies published way back in the March 1965 issue of Modern Photography, and, thanks to the protean scanning efforts of Marc Bergman you can refer to that here for a more detailed explanation of my comments above.

None of this addresses the matter of how to actually adjust the lens of your Fujica so that its infinity focus will be optimum. But I know the answer to that after viewing your video, so I’ll address that in the following post.
Cheers
Brett
  Reply With Quote

Old 08-03-2019   #9
Sarcophilus Harrisii
Brett Rogers
 
Sarcophilus Harrisii is offline
Join Date: Jun 2009
Posts: 2,648
Quote:
Originally Posted by johnnyrod View Post
Do you just line up the "start" line on the backing paper with the pair white arrows then close up and wind on to number 1?

I've made a video of about 3 minutes which might help understand the focus mechanism. There is a pin of about 4-5mm that locates the focus unit on the front standard. There is a small hole drilled in the front of the focus unit that locates a tiny screw head on the back of the shutter. Thus, the focus scale is in the right place on the standard, and the shutter body also lines up with the scale, so that when it's fully retracted, the focus scale shows infinity. The front two lens groups are turned in a single housing which screws in until it bottoms, equally the rear element screws in until it bottoms, so just like a Mamiya Six. There is a sleeve that screws onto the back of the shutter and attaches the shutter to the focus mechanism - this has to bottom as well otherwise they would rattle around i.e. it's not an adjuster. The error in the focus is about half of a helicoid thread, so it hasn't been put back in the wrong place,skipping a thread would throw it too far out the other way. The helicoid has two sliding screws to stop it just rotating, the ends of their travel correspond to shortest distance (about 4ft, on the focus scale) and infinity.
Anyway I am jiggered if I can figure out how to adjust this thing! Here's the video, it is uploading just now so give it half an hour or so from the time on this post if it isn't visible yet
https://youtu.be/B8sT8sfHVug
I would estimate a shim to correct the focus would be about 0.5mm thick, placed between the standard and the back of the shutter/focus assembly. It seems odd there appears to be no focus adjustment!
Too easy!
No shims needed.

Scroll through your video to the 32 second mark. It shows a good view of the inside front of the focus assembly. See those three brass screws fastening the brass washer? The washer clamps the helical to the focus ring. Just back those off a bit (don't remove them) and you can rotate the ring independently of the helical. I made a reference to something like this in my first post, but without knowing the details of the camera couldn't be any more specific.

To actually get the focus correct you'll need to:
  • Set the ring to infinity and keep it there;
  • Remove the shutter from the focus assembly and back off the those screws;
  • Temporarily re-assemble it all including, obviously, the lens components;
  • Inspect the lens focus at the film plane (at infinity, if you please) and adjust the helicals in their threads until the ground glass image is sharpest, then;
  • Without rotating the focus ring or lens, remove the shutter again so that the those screws can be tightened;
  • Re-check the ground glass one more time to verify the adjustment held while you tightened the fasteners and, if not;
  • Repeat as required, until it's spot on.
Let us know how you get on.
Cheers,
Brett
  Reply With Quote

Old 08-03-2019   #10
Steve M.
Registered User
 
Steve M. is offline
Join Date: Jun 2009
Posts: 3,382
If it's unit focus, yes, shimming the lens should do the trick. Could always reset the distance scale too. Are you using a ground glass and a loupe on the film rails? That's your gold standard for achieving accurate focus.
  Reply With Quote

Old 08-03-2019   #11
Solinar
Analog Preferred
 
Solinar's Avatar
 
Solinar is offline
Join Date: Aug 2004
Location: Austin, TX
Age: 65
Posts: 2,550


Whether you are using shims for a unit focusing lens or adjusting the collar on a lens that uses the front cell to focus - I prefer to set infinity by a method that is similar to a back focus collimator. Rather than describe it, just check out the link from Mike Elek below:

http://elekm.net/zeiss-ikon/repair/collimate/

It's best to use a long focal length lens on the viewing camera - which is an SLR. The viewing lens needs to be set to infinity.

I prefer to use some frosted glass from a 4x5 camera's focusing screen for a target. I had the focusing screen cut down to fit with the rails of the film gate by a glass shop. The target lines are on the unfrosted side, similar to what Mike Elek shows. The target lines simulate the emulsion side of the film.

The frosted side of glass cuts down any glare from the back-lit light source. It becomes a diffused light source.

When you are finished doing collimating the lens this way - flip the focusing screen over, so the frosted side of the glass faces the lens. Now, you can use a magnifying loupe to check the focus as you would on a medium format or large format Graflex.

Do you need to use a glass focusing screen for the back focus method to collimate the focus?

Nah! I've used a cut down CD/DVD jewel case before - or - you can go the low budget route >>>>> http://jamesharrphoto.blogspot.com/2014/05/
__________________
- Andrew in Austin, Texas -

35mm Gear Bessa R, Leica II, - IIIg, - M2
Just for fun 35mm Gear a Kodak Retina IIa, a Rollei 35 S, plus an Oly 35RD and a Voigtlander Vito II
Modern Medium Format Fuji GW 690III
Vintage MF Folders a Voigtländer Perkeo II and Bessa II, 2 of them - a ZI Mess Ikonta 524/2 - plus an Agfa Super Isolette & a Record III
Digital a D300 and a D700 with some primes - still going over a decade later

"Who spilled the Dektol on the bathroom carpet?"

Last edited by Solinar : 08-03-2019 at 05:31. Reason: Add photo
  Reply With Quote

Old 08-03-2019   #12
johnnyrod
More cameras than shots
 
johnnyrod is offline
Join Date: Jul 2014
Location: Doncaster, UK
Posts: 411
Brett - thanks for the info. I'm sure I slackened the three screws and it wouldn't turn, I'll check it again.
Regarding infinity or 5ft, I've never had a problem, and when I've used the split circle for 75mm MF folders it has been accurate at short range, which is when the problems show up the greatest. I say all that but with no disrepsect for your vast knowledge and experience.
I've seen Mike Elek's back-focus method before, but it relies on a "known good" lens - a secondary standard. A measuring tape or a tree in the distance is a primary standard. I'm a bit wary of labelling anything as perfect! I have wondered as an alternative if I could use the light and screen but at 5ft projected onto a wall, but to be honest it's just as easy to use a laptop screen, ground glass (or equivalent), and a loupe. Actually I had to abandon the split circle for an Ensign 820 with 105mm f3.9 lens as it tended to black out, and my holder was too flexible at the time.

No time to fiddle yet but will report back when done. Thanks all.
__________________
How does this thing work?
  Reply With Quote

Old 08-03-2019   #13
Sarcophilus Harrisii
Brett Rogers
 
Sarcophilus Harrisii is offline
Join Date: Jun 2009
Posts: 2,648
Yes "perfect" is very much a philosophical construct, whenever you up the resolution far enough of any measuring system, that which previously seemed "perfect" will be revealed not to be so. My use of the term wasn't intended to be literal.

I'm fairly sure the screws in question and the disc they fasten are the key to dialling the lens in. But the camera is several decades old. Although it shouldn't have been necessary when new, if backing off the screws fails to see any change, you may need to remove the screws and brass disc to investigate.

So that you don't run into any alignment problems, if you do remove them, first set the ring to infinity and don't rotate either the ring or helical while you extract the disc. It ought to then be possible to clean off any corrosion that might be problematic and re-install it without getting tied up in knots trying to restore the correct relationship between the focusing components.
Cheers,
Brett
  Reply With Quote

Old 08-03-2019   #14
Sarcophilus Harrisii
Brett Rogers
 
Sarcophilus Harrisii is offline
Join Date: Jun 2009
Posts: 2,648
More on split wedge RF SLR screens and what makes them optically good, and not so good, courtesy of Marc Bergman. In terms of calibrating a lens focus reliably, despite the disadvantages involved in a plain ground glass, I still think it is, overall, the most reliable way to assess focus at the film plane. But FYI.
Cheers
Brett
https://www.flickr.com/photos/385528...57710038219332
  Reply With Quote

Old 08-04-2019   #15
johnnyrod
More cameras than shots
 
johnnyrod is offline
Join Date: Jul 2014
Location: Doncaster, UK
Posts: 411
Hmm it was a good guess but no dice. The three brass screws hold the helicoid to the silver painted focus ring, which goes through the ring, nothing sandwiched. The screws pass through only the brass plate of the helicoid outer and screw straight into the focus ring, so there is no way to rotate anything. I eyed it up again and to skip a thread on the helicoid would be too much.
I'll have to have another look and take some more pics.
__________________
How does this thing work?
  Reply With Quote

Old 08-05-2019   #16
johnnyrod
More cameras than shots
 
johnnyrod is offline
Join Date: Jul 2014
Location: Doncaster, UK
Posts: 411
Another video, seems Youtube wants an hour to put this one up.
https://youtu.be/QsqB8sKyhio
It's only a bit over a minute long!
__________________
How does this thing work?
  Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -8. The time now is 05:30.


vBulletin skin developed by: eXtremepixels
Powered by vBulletin® Version 3.6.8
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.

All content on this site is Copyright Protected and owned by its respective owner. You may link to content on this site but you may not reproduce any of it in whole or part without written consent from its owner.