[dmr]

I just found this forum, and somewhat surprised that I have not seen it. I found it when looking for some Pentax lens issues via google. I've been on several camera forums for decades and for some reason have not stumbled on this one.

I posted this on Rangefinder Forum and APUG and if you don't mind I would like the opinions of the folks here, as there appears to be a lot of knowledge here.


Here's the issue, to make a long story long ...


My "main" camera for decades has been a Pentax K1000.

This is a first generation 1980s vintage Japanese model, all metal, well broken in and until a couple of years ago performing flawlessly. It's the one I feel very comfortable with and I can shoot it instinctively. It's never been physically damaged or even dropped onto a hard surface that I know of.

A few years ago some of the slides I shot on a trip to some of the National Parks came back disappointingly soft. This was shooting with an Ozunon 28-135 zoom of 1990s vintage which until then had been tack sharp. I did a quick test roll at the time which was really inconclusive.


To be sure, I picked up a Takumar 28-80 zoom at a local camera show, shot with that for a while with what I considered good results, and blamed the issue on the Ozunon zoom.


Fast forward to a couple of months ago. A roll I shot with the Pentax zoom came back with some disappointingly soft images, mainly those with images off in the distance where I would have focused on infinity.


I decided to do some more rigorous testing and I would like to hear what the gang here thinks.


First of all, two "control" images are at the very bottom of the post. These were taken of the same subjects but not at the same time. I'm including them to show what I consider "normal" and what I'm expecting. The control images were shot with the Mamiya SD rangefinder but well before the test roll on the Pentax.


All of these images were (re)scanned with the KM SD IV at full 3200 resolution, absolutely no sharpening or photoshopping at all. These are all 500x500 full size crops and all show the grain very well. For the real-world shots on all but the control, I centered on what I and the neighbors call "the big honking nest" in the trees in the woods to the rear. The nest was center-left in the control image.


K1000 with 50mm f2.0 prime lens f16:





This one above was taken with the lens set hard to infinity. When comparing with the control image below it appears a wee bit softer to me, but when viewed as a whole image on the screen, there's really no difference. The image appears normal when viewed normally.


Test target 50mm f2.0 prime lens f16:





This is the test target at maybe 6' or so, f16, daylight, manually focused (I did wear my glasses!) . It looks very normal to me.
. . . . . . . . . .


K1000 with Takumar-A 28-80mm zoom:


28mm f16:





The shot above was at 28mm with the focus set hard to infinity. Comparing it to the control photo and the prime lens photo above, it appears to be to be somewhat softer. When viewed at a normal size on the monitor it still looks quite normal.


80mm f16:





This shot above was zoomed out to the max with the focus set hard to infinity, f16. To me, this looks unacceptably soft. When viewed on the monitor it's normal or near-normal, but a 8.5x11 print does appear soft to me.


80mm f5.6:





This is overexposed. I wanted to see what it would do in the middle of the f stop range so it was f5.6 at 1/1000. The softness is REALLY showing here!
. . . . .


K1000 Ozunon 28-135 zoom:


I'm not posting the 28 or 50mm Ozunon shots since they look near normal but when I zoom it way out to 135, the softness is unacceptable at f16 and UGLY at f5.6!


135mm f16:





135mm f5.6:





Test target:





The shot immediately above is with the Ozunon zoomed out to 135 at about 10' from the target. It looks normal to me. It was carefully focused while wearing glasses.
. . . . . . . . . .


I'm not really sure what my conclusion is, and I would appreciate other opinions. I'm leaning toward thinking I might have a bad body but I'm not sure. The prime kit lens, which I really don't shoot with that much, appears to be near-normal at worst but both zooms are producing unacceptably soft images.


. . . . . . . . . .


"Control" photos:


Not the same roll, obviously, not the same light, and not the same day. These were taken with the Mamiya SD rangefinder, match-needle exposure on the outside shot, exact exposure not remembered but something like 1/500 between f11 and f8 or so. The test target was done indoor with fllash some time before.








Thanks for any advice or opinions, gang!

Here's the issue, to make a long story long ...


My "main" camera for decades has been a Pentax K1000. This is a first generation 1980s vintage Japanese model, all metal, well broken in and until a couple of years ago performing flawlessly. It's the one I feel very comfortable with and I can shoot it instinctively. It's never been physically damaged or even dropped onto a hard surface that I know of.


A few years ago some of the slides I shot on a trip to some of the National Parks came back disappointingly soft. This was shooting with an Ozunon 28-135 zoom of 1990s vintage which until then had been tack sharp. I did a quick test roll at the time which was really inconclusive.


To be sure, I picked up a Takumar 28-80 zoom at a local camera show, shot with that for a while with what I considered good results, and blamed the issue on the Ozunon zoom.


Fast forward to a couple of months ago. A roll I shot with the Pentax zoom came back with some disappointingly soft images, mainly those with images off in the distance where I would have focused on infinity.


I decided to do some more rigorous testing and I would like to hear what the gang here thinks.


First of all, two "control" images are at the very bottom of the post. These were taken of the same subjects but not at the same time. I'm including them to show what I consider "normal" and what I'm expecting. The control images were shot with the Mamiya SD rangefinder but well before the test roll on the Pentax.


All of these images were (re)scanned with the KM SD IV at full 3200 resolution, absolutely no sharpening or photoshopping at all. These are all 500x500 full size crops and all show the grain very well. For the real-world shots on all but the control, I centered on what I and the neighbors call "the big honking nest" in the trees in the woods to the rear. The nest was center-left in the control image.


K1000 with 50mm f2.0 prime lens f16:





This one above was taken with the lens set hard to infinity. When comparing with the control image below it appears a wee bit softer to me, but when viewed as a whole image on the screen, there's really no difference. The image appears normal when viewed normally.


Test target 50mm f2.0 prime lens f16:





This is the test target at maybe 6' or so, f16, daylight, manually focused (I did wear my glasses!) . It looks very normal to me.
. . . . . . . . . .


K1000 with Takumar-A 28-80mm zoom:


28mm f16:





The shot above was at 28mm with the focus set hard to infinity. Comparing it to the control photo and the prime lens photo above, it appears to be to be somewhat softer. When viewed at a normal size on the monitor it still looks quite normal.


80mm f16:





This shot above was zoomed out to the max with the focus set hard to infinity, f16. To me, this looks unacceptably soft. When viewed on the monitor it's normal or near-normal, but a 8.5x11 print does appear soft to me.


80mm f5.6:





This is overexposed. I wanted to see what it would do in the middle of the f stop range so it was f5.6 at 1/1000. The softness is REALLY showing here!
. . . . .


K1000 Ozunon 28-135 zoom:


I'm not posting the 28 or 50mm Ozunon shots since they look near normal but when I zoom it way out to 135, the softness is unacceptable at f16 and UGLY at f5.6!


135mm f16:





135mm f5.6:





Test target:





The shot immediately above is with the Ozunon zoomed out to 135 at about 10' from the target. It looks normal to me. It was carefully focused while wearing glasses.
. . . . . . . . . .


I'm not really sure what my conclusion is, and I would appreciate other opinions. I'm leaning toward thinking I might have a bad body but I'm not sure. The prime kit lens, which I really don't shoot with that much, appears to be near-normal at worst but both zooms are producing unacceptably soft images.


. . . . . . . . . .


"Control" photos:


Not the same roll, obviously, not the same light, and not the same day. These were taken with the Mamiya SD rangefinder, match-needle exposure on the outside shot, exact exposure not remembered but something like 1/500 between f11 and f8 or so. The test target was done indoor with fllash some time before.








As an update since I first posted this on the other two forums (fora?) one of the users suggested I do a "focal plane test" shooting something like a brick wall and seeing if the focus I see is indeed what I get. Another off-line comment seemed to think that the infinity stops of both zooms are bad but that of the prime looks good. Second opinions on both of those are appreciated as well.

Thanks for any advice or opinions, gang!

[Adam]

It might be worth getting another K1000 (CLAd of course) to test your theory about the body.

But it might be even easier just to see if the lens is at fault by doing some controlled tests with it on digital, focusing using magnified live view.

It's perfectly normal for cheap zooms like the 28-135 to be soft wide-open, and at F16 there can be diffraction. In addition, at tele zoom settings even slight inaccuracies in the focus might show. Since you're pixel-peeping I wouldn't be too suprosed by the results. My theory is that it's a combination of bad luck (with focusing) and the general performance of the lens.

Another approach would be to use a viewfinder magnifier. Pentax's refconvereter is very nice for that purpose. Hope this helps!

[photoptimist]

A few thoughts:

First, I'd avoid using the infinity mark on any lens but especially a zoom. The manufacturing tolerances on a lens are stacked to ensure the lens can reach infinity despite variations in temperature and variations in the dimensions of the camera. The result is that infinity focus is often a hair back from the infinity mark. Age and wear can make this worse.

Second, tests for focusing typically use the lens wide open and focus on a scene with a wide range of distances (e.g., shooting a ruler or brick wall from an oblique angle so that most of the foreground and background are out of focus and only a center mark should be in-focus). That creates photos that are especially sensitive to missed focus and can test whether the true plane of focus is behind or in-front of the one chosen by careful focusing.

Third, wear (or accumulated grime) in the mirror mechanism can induce a shift between focus plane for the viewfinder and that for the film.

Good luck!

[patrick9]

You say that you have the lens set to Hard infinity. Most of my zooms are off at hard infinity. I have to back them off a touch to get a sharper image Especially my older ones. I am wondering if you may be getting the same issue where the stop for infinity focus is off . I would agree with a digital body to test the lenses on.

[Just1MoreDave]

While K1000s appear to just churn along, a little professional maintenance every 30-40 years can't hurt.

I have read somewhere about using ground glass where the film would go. Then you could see if the image projected onto the film plane has a different point of focus than what you see in the viewfinder. You'd have to find something to use as ground glass. I'd get some Lexan or acrylic from Home Depot (window repair aisle) and see if simply sanding it with a fine grit paper would work. If that works, you have to place it exactly where the film would be. It may be easier to remove the film door so it's not constantly flapping in the way. Then you almost have a DSLR in Live View. Maybe magnify with a loupe?

I think it's easier to compare the film view to viewfinder with the 50mm and minimum distance because the point of focus is way easier to see. I know your problem seems to be at infinity but if it's a camera problem, I can't imagine a way for infinity to be off without issues at all distances. I have a hard time seeing the exact sharpest point at large distances. One idea is to try looking at a distant light source at night, like a street light. You can focus until the light is as small as possible. The moon works too. But I'd try short distances too.

I don't know what you'd do next if you see a camera problem. If I remember right, the focus screen on a K1000 isn't easy to remove, so you can't shim it. The problem could be a pentaprism or the mirror out of position. If the problem seems to be in the lenses, it should be really easy to find inexpensive replacements that are better. I had a really awesome SMC Pentax-A 28-135 f4 that I sold for only $50 several years ago.

[Alex645]

It is very rare for a film camera to cause lack of sharpness. Possible explanations?
a) The lens mount being slightly bent/damaged and thus out of alignment, or
b) The back pressure plate not holding the film flat and perpendicular to the lens.
c) A slow enough shutter speed can also cause blur, depending on subject & camera movement and your focal length. If your lens dampening foam is worn, mirror slap can cause enough internal vibration that is detectable in pixel peeping unless youʻre over 1/250".

This of course is assuming that you are examining the actual negs or slides on a loupe. If not, then the scanning or printing technique can compound or cause soft images too. Every print is made by at least two lenses: the one on the camera and the one on the enlarger or print processor.

If you eliminate the camera and scan/printing causation, then it is the lens. Generally speaking, zooms shouldnʻt be compared to primes, and are more complicated in testing various focal lengths, distances, and apertures. Also in general, as mentioned by others, lenses generally perform best in the middle of their ranges, whether focal length, hyperfocal distances, or apertures. I would expect most lenses to not perform well at their largest apertures due to depth-of-field and other resolution issues, nor at their smallest due to diffraction. With your f/2 50mm prime, Iʻd test it around f/5.6 and with an f/4 zoom, try f/8.

My own eyesight is not what it used to be for manual focusing and Iʻve had more issues with soft focus recently then when I was younger. Because of this, I shoot less wide open then I used to, and because of this, higher ISO films (400 vs. 100). When I do, I bracket my focus.

[Just1MoreDave]

... You'd have to find something to use as ground glass. I'd get some Lexan or acrylic from Home Depot (window repair aisle) and see if simply sanding it with a fine grit paper would work. If that works, you have to place it exactly where the film would be. It may be easier to remove the film door so it's not constantly flapping in the way. Then you almost have a DSLR in Live View. Maybe magnify with a loupe?

I just tried this to see if I was full of crap or not. I used acrylic because I came across it first. I think the best sandpaper grit is something like P600. The more random a scratch pattern you can make, the better the image will look. You can make the acrylic slightly less than the width of film and it'll fit between the guide rails.

[dmr]

Thanks everyone! I'm copying a note I just made on one of the other systems to avoid typing it all again, I hope you don't mind. This was about a test roll I shot just a while ago using some railroad tracks as a scale to see where the plane of best focus is on all the lenses.

Thanks everyone. Here's an update. I just got back from shooting a test roll and I did have a couple of "ah-ha" incidents and I think I have a MUCH better handle on this.

I was alone, no distractions, bright afternoon sun, and several hours after my breakfast club champagne brunch so I was alert and bright-eyed and bushy-tailed and no distractions. Just me and the camera. I wore my regular glasses and not my prescription sunglasses, which are, technically, an older prescription.

Now let's see if my test roll verifies what I saw in the viewfinder. I'll probably get that back Tuesday. Here are the high points:

1. First the 50mm prime, which I don't use that much. When very carefully focusing, using the center ground glass, on some trees more than a mile away, the prime lens most definitely focuses THROUGH infinity very slightly. No visible change in the viewfinder or the focus point between shots.

2. Second was the Takumar 28-80 zoom. I first set it at about 50mm for a good comparison between it and the prime, and at first it most definitely did NOT come into clear focus at infinity. I could, however, focus easily on the tracks about 15 feet ahead of me.

THEN I exercised the zoom and the focus a bit and when I put it into and out of "macro" mode, which I never use, something kinda "clicked" and from that point on it would very clearly focus slightly through infinity. I could not get it to "click back" to the bad mode but I'lll play with it a bit more after I watch the news and get something to eat.

3. Third was the Ozunon 28-135 zoom. This is DEFINITELY wonky! At 28 it appeared that I could BARELY get the switch light tower down the track a bit in focus right at the infinity stop but at 135, looking closely, it was bad. The point of clear focus at 135, hard against the infinity stop, was maybe 20-25 feet on the track in front of me! I unmounted and remounted to be sure I had it securely in place but it would not clearly focus at infinity when zoomed out. Let's see if the test roll agrees with what I saw in the viewfinder.

I know the local camera shop has a place they send lenses for service and tomorrow I'm gonna ask how much it would be to have both of the zooms looked at. Unfortunately, I have a feeling that service will cost more than the lenses are worth.

Thanks again everyone.