TLR Lens testing

[Kirks518]

So I was given a lens for my C220, but it's pretty ratty. The both the viewing and taking lenses have issues, but I'm not concerned about the viewing lens as much as the taking lens. I see scratching on the rear elements, both the out and the inner elements. Not a great thing.

Anyway, with an SLR, I can usually tell how awful the resulting image will be with a bad lens, but with a TLR, I'm guessing I'll have to shoot a test frame or two to see if it's at all usable. So what do you all use as a target/subject for this time of thing? I do have a resolution chart mounted on a wall in the mudroom (much to my wife's chagrin), but I'm wondering if there is a better or easier way to check it out.

 

[grahamp]

Flare might be a bigger problem than resolution. These lenses do need a good lens hood even when perfect. The test target at the right distance and with careful alignment will give you a baseline for raw performance on a general purpose emulsion. I would do 3-4 test target shots, then do some general shots with various lighting conditions.

 

[pbromaghin]

The pads holding the ground glass can deteriorate, throwing the focusing out of wack. Try a couple at 45 degrees to 1)a wall with a lot of texture from several feet away, and 2)a newspaper from close enough to see the print. Clearly mark a target X. This will tell you if both lenses agree on focus distance.

 

[flavio81]

The pads holding the ground glass can deteriorate, throwing the focusing out of wack. Try a couple at 45 degrees to 1)a wall with a lot of texture from several feet away, and 2)a newspaper from close enough to see the print. Clearly mark a target X. This will tell you if both lenses agree on focus distance.

True but this is something you can repair. And it happens only on the C330 series, which have interchangeable screens.

My suggestion would be just to make sure the retaining ring on the lenses (which keep each lens retained on the lens plate) are tight and there's no play when grabbing the lens and trying to twist it.

As for the scratches, they will only reduce contrast, not resolution. If you want to see the effect on image (without having to shoot film), there are two ways: (I'm assuming you are using the 80mm lens)

a. Remove the front and rear elements of the taking lens (they just unscrew !!) and swap them with the viewing lens. Then assess the impact on image quality.

b. Get a ground-glass (or you can make yourself one by cutting CD jewel case plastic and sanding one side), place ground glass and assess if the contrast of the resulting image is good.

Small scratches will usually make little effect. On the other hand, fungus, or coatings which are permanently damaged by fungus (turned hazy instead of crystal clear) will have a big impact.

Scratches that are deep and easily noticeable can be filed out with black ink; this will reduce the impact of the scratches in contrast.

 

[Gerald C Koch]

I remember the story of a news photographer on location. He had dropped and cracked the front element of his normal lens. There was not enough time to get another. The crack was about 2/3 of the way from the center of the lens. He used black paint to make a thin line over the crack. He then continued on the assignment and the photos were fine. Why did this work? According to the laws of optics no lens can focus on it's own surface and all portions of a lens contribute to all portions of the image. Therefore surface scratches will have little effect on resolution. However they will contribute a bit to flare. That is why the photographer painted over the crack.

 

[Kirks518]

I completely took apart the lens (Mamiya 180mm 4.5, old version), and took the best individual elements and put those into the taking lens, and the really bad ones went into the viewing lens.

Almost every element had either scratches or haze, and there seems to be haze between the elements of the second element from the rear, so really this lens is toast. But, I will shoot a few shots with it, including the resolution chart, simply because it's black and white, so I should get a good idea of how bad of a contrast loss I'll have.

Now if I could find one with a bad shutter and good glass....

 

[pbromaghin]

True but this is something you can repair. And it happens only on the C330 series, which have interchangeable screens.

Of course it is something you can repair. That's why he should do the test. Also, it is not restricted to the C-330. The C-33 is equally susceptible to it and is more fiddly to repair and re-adjust.

 

[Kirks518]

Oh, forgot to mention, it's a C220, so (I'm guessing here) the above about the GG pads is not applicable? I haven't had any focusing problems with the camera using the 80mm or the 55mm.

 

[Nick Merritt]

I got an old version of the 180/4.5 ("silver" model) with significant haze on interior surfaces of both lenses, which did not clean up. It, along with the C33 and two other lenses it came with, had obviously been kept in a damp environment. But using the lens with the proper hood, the results I have gotten are fine, perhaps slightly more flare but nothing significant. It's a very sharp lens design. No, I have not pointed it directly at a strong light source, but that's a relatively small concession to its condition.

Test out the lens and see how you do -- I bet you will be pleasantly surprised.

 

[pbromaghin]

Oh, forgot to mention, it's a C220, so (I'm guessing here) the above about the GG pads is not applicable? I haven't had any focusing problems with the camera using the 80mm or the 55mm.

Well, the C-220 was concurrent with the C-330, and I don't really know how close they were. But if you haven't had any problem, you haven't had any problem. Go for it, these are wonderful cameras! I absolutely love my C-33.

 

[flavio81]

I completely took apart the lens (Mamiya 180mm 4.5, old version), and took the best individual elements and put those into the taking lens, and the really bad ones went into the viewing lens.

Almost every element had either scratches or haze, and there seems to be haze between the elements of the second element from the rear, so really this lens is toast. But, I will shoot a few shots with it, including the resolution chart, simply because it's black and white, so I should get a good idea of how bad of a contrast loss I'll have.

In the old 180/4.5 the typical problem is that the rear lens, or one of the rear surfaces, develop a haze.

This haze can be cleaned by aggressive methods (i'd guess using toothpaste or some similar polishing compound?). Been there, had that lens (180/4.5), my technician cleaned most (but not all) of the haze. Afterwards, it was a very very good lens, sharp and with one of the best bokeh i've ever seen in a lens. I sold it, now got the "super" version, and sometimes i think the bokeh was better on the old lens.

 

[Kirks518]

Well, shot the second half of a roll with the lens to test it out.

(there was a url link here which no longer exists)

Test was inconclusive at this point.....

 

[RalphLambrecht]

So I was given a lens for my C220, but it's pretty ratty. The both the viewing and taking lenses have issues, but I'm not concerned about the viewing lens as much as the taking lens. I see scratching on the rear elements, both the out and the inner elements. Not a great thing.

Anyway, with an SLR, I can usually tell how awful the resulting image will be with a bad lens, but with a TLR, I'm guessing I'll have to shoot a test frame or two to see if it's at all usable. So what do you all use as a target/subject for this time of thing? I do have a resolution chart mounted on a wall in the mudroom (much to my wife's chagrin), but I'm wondering if there is a better or easier way to check it out.

test targets such as a USAF1951 can give yousome objective results but you are better off taking a photograph of a ,for you, typical subject to determine the lens' value for your photography