2016 May 23    Film   Medium & Large Format,   Camera Repair



Introduction


A reader sent me the above photo, asking what might cause this.  He says the camera pressure-plate is correct for the film type (120, not 220).  How would you go about fixing this?

If your film is blurry in one area, especially the center, then you'd probably benefit from this other article.  If it's blurry everywhere in the photo, as shown in the example above, then chances are that your TLR has a focusing problem. 

This article applies to Yashica MAT cameras, but it should also hold true for most other TLR (twin-lens reflex) cameras.  They all have a viewing lens (the upper one, which transmits light to your eye) and a taking lens (the lower one, which transmits light to the film.)

Now let's see how to diagnose and fix TLR focusing problems.


A Quick Note

This article and website are made possible only with the support of readers like you, when you use the links on here to purchase your gear. 

The small commissions from sales are what allow me to keep this site going.   Thank you in advance for your help.




In This Article


Before You Do Anything Else

Checking Focus on the Taking Lens

What Can Cause Mis-Focus

The Ground Glass

If It's The Taking Lens

If It's The Focus Knob

Conclusion




Before You Do Anything Else


UPDATE!   Before you do anything else, look at the camera lenses.  Your Yashica MAT camera should have two Yashinon lenses, both 80mm. 

If one is 80mm and one is 60mm or some other focal length, that's going to make blurry pictures.  The reader who sent me the blurry photo emailed back after he noticed this.  I wouldn't expect this to happen with most TLR's, simply because anyone who did this would quickly find that the camera was unusable.  For some reason, his particular Yashica MAT had this problem.  Maybe someone started to replace the lenses with a different focal length, then couldn't get one of the spanner rings out or something.

Again, the taking lens and the viewing lens have to be the same focal length.  If you use two different focal lengths, I think they will have one focus point where they match, but everywhere else will be off. 

If the viewing lens and the taking lens are two different focal lengths, you may need to buy yourself a parts camera to get the lens set that you need.  The taking lens has to be removed in two parts, the front element and the rear element.  They are separated by the aperture and shutter assembly, which stays in the camera. 

Both these elements have a slotted ring holding them in place;  this must be removed with a spanner tool.  Some people use specially-ground hemostats to do this, especially for the rear element.  (Yep, if you're planning to do camera repair, you'll want one of these too.)  The camera housing dimensions won't accommodate most other types of spanner tools.

If you know the lens focal lengths are both the same, here's the original "Before You Do Everything Else" section of this article:


Put the camera on a tripod and set the aperture to its widest (f/3.5 on a Yashica MAT).  Point the camera at some object placed at a carefully-measured distance from the back of the camera.  I chose seven feet because I already took a picture of the focus knob set at seven.  You would actually be better off choosing 3.3 feet, because focus errors will be more obvious there.  (Depth of field is shortest.) 

Yashica TLR's measure their focus distance from the back of the camera, which is almost the same as measuring from the film plane.  So, hook the tape measure to the back of the camera and measure from there (toward the front, of course).  3.3 feet is about 3 ft 3 5/8-inches.

A newspaper headline is a good focus target.  The newspaper should be parallel to the front of the camera. 

As you normally would, look through the viewfinder and focus on the object.

Now check the numbers on the focus knob.  On the Yashica MAT cameras, the dot in "3.5" is where you line up the focal-distance numbers.  Sometimes there will be a vertical mark beneath it.  There are lines on either side of 3.5;  these indicate the ultra-short hyperfocal distance for f/3.5.  You line up the focus halfway between those two lines, right under the dot. 

Look at the number that shows underneath that dot.  If that number doesn't correspond with the distance at which you set the object, that's a problem.  If the number doesn't line up exactly, that's also a problem.

If that happens, there's a good possibility that there's some problem in the viewing lens path.  Because the viewing lens is your reference point for all focusing, any problem there is going to translate to blurry pictures.

There's also the possibility that the focus knob is simply misaligned.  To find out of this is happening, you'll need to check focus on the taking lens, as well.  That's a little more involved, but not really that difficult.


Back to Top

Table of Contents



Checking Focus on the Taking Lens


You may want to do this even if you think the viewing lens path is the problem. 

1.  You'll need a flat piece of frosted or ground glass.  It should fit across the film rails, as if it were a piece of 120 film.  It has to be in the exact plane where the film would be, otherwise none of this will work.

2.  Open up the back of the camera and secure the ground glass where the film would be.  Blue masking tape or rubber bands can work.  Don't use anything that leaves adhesive residue on the film transport path, for obvious reasons.

3.  Ideally, first check the taking-lens focus on some very distant object.  This is your infinity focus.  If it won't even focus on infinity, that's a problem.  If the viewing lens also won't focus on infinity, then your focus knob / mechanism is probably misaligned.  If the viewing lens will focus on infinity but the taking lens won't... then it's probably the taking lens.

4.  Now check the focus on something close.  Pick a number that's displayed on the focus knob.  Again, I would choose the closest focus, usually 3.3 feet.  Measure out carefully to that distance.  Put some object there, at that exact distance.  Ideally it should be something with good contrast, like a newspaper headline.

5.  Now, adjust the focus knob to that measured distance.  Or, watch the ground glass and focus on the object, then check the focus knob and see if the number is correct.

6.  If the taking lens is in focus at the correct distance, but the viewing lens is not in focus, then you know the viewing lens is the problem.

7.  Make sure you don't bump the camera while checking the focus.  With a Yashica MAT, you can't put the camera on a tripod when the back is open.


Back to Top

Table of Contents



What Can Cause Mis-Focus


-  Mirror is loose / out of alignment.  To get to the mirror you have to remove the viewfinder assembly, which is held on with four screws.  (Set of these highly recommended.)

-  Ground glass was installed upside-down by someone who tried to fix the camera.  Easy to diagnose;  see next section.

-  Viewing lens is not screwed in properly.   The viewing lens elements are held in with spanner collars, just like the taking lens elements.

- Focus knob is misaligned or loose.  This would manifest as the taking lens and the viewing lens both having the same focus error. 

- Someone could even have put in the wrong lens element.  Maybe they had a lens from another camera that just happens to have the same thread pitch.  Maybe they even thought they were using the correct lens element and can't figure out why the pictures are blurry!

If you buy the camera on Ebay and the seller says "untested", any of these-- or all of them-- could be possible.  You could be buying someone's attempted repair job where they had no idea what they were doing.  This is why "film tested" cameras are always the best.  If your Yashica MAT has to sit around half-disassembled for a while, consider getting yourself an already-tested or serviced one for the meantime.  Otherwise you'll miss out on good film pictures for that whole time!


Back to Top

Table of Contents


The Ground Glass


This one is really easy to diagnose. 

On [all?] the Yashica MAT's, the visual alignment grid should be on the smooth side of the glass.  If it looks like the one that's shown in the photo, then the ground glass is right-side up and it's OK.  There's always the possibility that it's loose, but you should be able to test that easily.

If you're not sure which is the frosted side, try this.  Open the flip-top of the Yashica MAT.  The magnifying glass should be folded out of the way.  Now, tilt the camera until you can see the reflection of something bright, such as an incandescent light bulb filament.  If the reflection is clear and sharp, then the ground glass is right-side-up.  If the reflection is hazy or diffuse, then someone put the ground glass in upside-down.

It's the same principle you would use to find the correct side of the Anti-Newton-Ring glass when macro-scanning film.


Back to Top

Table of Contents



If It's The Taking Lens


If the viewing-lens path is OK, then the numbers on the focus knob will match up with your correctly-measured distances.  Just to be sure, test the minimum focus distance and also the infinity focus.

If those are OK, then the problem is with the taking lens.  At this point, it cannot be "both" (i.e., misaligned focus knob), because the viewing lens and the taking lens are on the same platform which moves forward and back as you turn the knob.  So, once again... if the viewing lens is focusing to the correct distances, then the taking lens must be the problem.

That's actually pretty easy to fix.

Both the front and the rear elements can be removed with a spanner tool.  Actually, the ready-made tools might not be able to reach the rear element;  you might have to cobble up your own spanner tool.  That's part of what I like to call "frontier metalworking";  until I write that article, start with this one.

If you're sure you've narrowed the problem to your taking lens, it could be that one of the elements has backed out of the screw threads.  Fix it, then re-check the focus using a piece of ground glass against the film rails.  As long as the taking-lens elements are bottomed out in the threads, they should be in proper focus. 


Back to Top

Table of Contents



If It's The Focus Knob


Misaligned focus knob would mean that the taking lens and the viewing lens would both be out of focus across the same range of distances.  To verify this, you'd have to have tested both the viewing lens and the taking lens, using the methods I've described earlier.

If it's the focus knob, this problem is not really that difficult to fix.  I've not yet had to do this myself, but there's a plastic cap in the center of the focus knob.  On some [all?] Yashica MAT cameras, you remove this with a spanner tool;  The spanner holes are very difficult to see without very good light and some magnification.

There is a nut that tightens the knob so that it doesn't rotate about the axis of the focusing shaft.  This could be loose.  Or, it could have been tightened at the wrong position. 

To align it, you'd have to focus the camera at infinity (or some measured distance), then rotate the loosened knob to the correct position and tighten it down.


Back to Top

Table of Contents


Conclusion


Diagnosing these problems is not as difficult as fixing some of them, but it's still hugely important.  Most of us can relate some story where we took apart something, only to find out it was the wrong thing.  Correct diagnosis really goes a long way.

Focus problems on a Yashica MAT are generally not that difficult to fix yourself;  I can't speak for every other TLR out there, though. 

Just by looking at that sample photo sent by the reader, I'm going to guess it's either (A.) a lens element is not tightened correctly, or (B.) the focus knob is misaligned.  To be sure, you'd have to go through the steps that we've looked at here.

Update:  The reader's TLR had two different focal lengths for the taking lens and viewing lens.  This is not supposed to happen.  Someone installed a 60mm lens in one, but not the other.  The solution is to make sure the camera has two 80mm lens sets:  One for the viewing lens, and one for the taking lens.

There are plenty of other problems (such as the film transport issue) that you might not want / feel confident to tackle yourself.  In that case, professional repair is money well-spent.  And actually, given the amount of work to do a good CLA or repair job, the work is usually a bargain from a good repair shop.  Send out your camera to a good shop, then use your working backup camera to go out and take pictures in the meantime.  Medium format!  How can you ever get enough of that, unless you've just gone and skipped ahead to large format already? 

This has been a look at focus problems on the Yashica MAT and other TLR's, most of which have a similar design.  Hopefully you've found this article helpful, and it has at least pointed you in the right direction.  If so, please help me out by using any of the links on here to purchase your gear.  It's the only way I can keep this site on-line and continue bringing you helpful articles.

Thanks for visiting this website!





         


Contact me:

3 p o.t o . 1 2 0 s t u d i o.. c o m


This won't directly copy and paste.  Please manually type it into your mail program.
No spaces between letters.





Home Page


Site Map


What's New!




Disclaimer

Copyright 2015










Back to Top of Page