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11-19-2014, 02:17 PM   #1
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Can't focus

I have been shooting pictures as a serious amateur for many years. Used many different cameras and lenses too. I want to say to start with that I'm not a beginner, but I just want to ask about a cheap Pentax brand 55-200mm MF zoom lens I got and am very frustrated with.
My problem is, that I can't seem to get a good, sharp focus on my subject. Nearby, yes, in front, or behind my subject yes, but it is almost a matter of "luck" if I happen to get my subject in focus. Stupid huh?
I get the little red box, that flashes and beeps when my camera thinks it is focused. Sometimes I shoot then, but sometimes, it just doesn't "look in focus", even though my camera insists it is. Could that be my problem? I shouldn't trust my camera? The only alternative is not to trust my eye!
Anyway, I'm made dozens of pictures with this used lens I got, and about 75% of them turn out bad because of focus. It literally is like hit or miss, and that is really annoying when you can't trust your equipment....or your eye! I guess after 40+ years of shooting pictures, I need to learn how to focus, huh? Or else get a new lens. <haha>

Any suggestions would be apprecaited.

Just a little background, I am on an extremely tight budget, so I can't do what I want to do - go buy a good lens - at this time. I am using an old, but still working well (with its kit lens anyway) *ist DS.

Scott (Astronomersmith)

11-19-2014, 02:47 PM - 1 Like   #2
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Can you be more specific about the exact lens? Not sure I recall there being a 55-200, the exact model number might help.
Since you are fairly experienced you may already know all these but here are a few things to check.

First, you say it is a MF lens, I assume that is manual focus not medium format? If so then the Auto focus system of the camera is not focusing the lens but is lighting the focus confirm lights in the viewfinder. Those lights are not particularly accurate and represent a 'zone' more than a particular spot, so there may be something in focus just not what you want.

Second, check your diopter settings, if the AF confirm and your eye do not agree something is out of adjustment and that might be the diopter, easy to check and an easy fix if it is.

Third, it is possible your focusing screen (the ground glass you focus with) has become misaligned or loose. Not likely, but possible. If so this can be fixed or shimmed to be correct. But this is not something to mess with until all other options have been exhausted.

Fourth, have you done any really controlled tests to remove other factors? Put the camera on a tripod and focus on a brick wall or something. Try it with the AF confirm light and with your eye.

Fifth, it is possible, but highly unlikely that the lens is decentered or has some other issue. Much more likely to be a lens issue if it was an AF lens as the AF system can have problems. Manual focus does not have a lot that can go wrong.
11-19-2014, 02:56 PM   #3
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QuoteOriginally posted by jatrax Quote
Can you be more specific about the exact lens? Not sure I recall there being a 55-200, the exact model number might help.
Since you are fairly experienced you may already know all these but here are a few things to check.

First, you say it is a MF lens, I assume that is manual focus not medium format? If so then the Auto focus system of the camera is not focusing the lens but is lighting the focus confirm lights in the viewfinder. Those lights are not particularly accurate and represent a 'zone' more than a particular spot, so there may be something in focus just not what you want.

Second, check your diopter settings, if the AF confirm and your eye do not agree something is out of adjustment and that might be the diopter, easy to check and an easy fix if it is.

Third, it is possible your focusing screen (the ground glass you focus with) has become misaligned or loose. Not likely, but possible. If so this can be fixed or shimmed to be correct. But this is not something to mess with until all other options have been exhausted.

Fourth, have you done any really controlled tests to remove other factors? Put the camera on a tripod and focus on a brick wall or something. Try it with the AF confirm light and with your eye.

Fifth, it is possible, but highly unlikely that the lens is decentered or has some other issue. Much more likely to be a lens issue if it was an AF lens as the AF system can have problems. Manual focus does not have a lot that can go wrong.
Jatrax,
I'm sorry. That was my mistake. I don't have it with me right now, so I can't give you the full details, but I did mess up. It is a 70-200mm manual focus lens. One other thing, it is really "loose" and way too smooth to turn when focusing. Like I said, it is probably a cheap kit lens from years ago, I'm guessing at least 00's or maybe even 90's.
Oh, well, you just taught me something! I didn't know that the AF system of the camera did that on a manual lens - I was just assuming it "thought" it sensed a good focus. That helps some right there! I'll have to think about your other suggestions, but that may very well be my problem in your first thought! Thanks!

Scott
11-19-2014, 03:04 PM   #4
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So you're actually using manual focus? it can be tough. Why not get a modern AF not-so-expensive lens and see how it goes?

I'm a big fan of manual focus but only when it comes to shooting landscapes on a tripod ) which is really not so much. I suck at manual focus for events and shooting people. I just don't have the dexterity. I know a girl who's using manual focus for shooting events in low light at f/1.4 and such, I don't understand how she does it, she catches focus like 90% of the time. I find it amazing but I'll stick to AF for this kind of stuff, thank you very much

11-19-2014, 03:18 PM   #5
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QuoteOriginally posted by Astronomersmith Quote
It is a 70-200mm manual focus lens. One other thing, it is really "loose" and way too smooth to turn when focusing. Like I said, it is probably a cheap kit lens from years ago, I'm guessing at least 00's or maybe even 90's.
If you get a chance post back with the full lens model description. Pentax has a long history and it is easy to confuse one model with another unless you describe it precisely. Just one letter off can be a completely different lens.

I still do not find a 70-200 in Pentax brand but they did make a 70-210 such as this one: SMC Pentax-A 70-210mm F4 Reviews - A Zoom Lenses - Pentax Lens Reviews & Lens Database which was fairly highly regarded. The 'cheap' kit lenses were later in the F and FA series and those are AF lenses. Still, zooms of that age were not optically that great, modern zooms are almost always better as opposed to prime lenses where the older ones seem to hold up much better compared to modern ones.

If it is a push / pull design in my experience the focus is much looser than say a prime lens of the same age. I used to have a 75-150mm zoom and the focus was quite smooth and maybe a touch too loose. So that is not for sure a sign that anything is wrong.

QuoteOriginally posted by Astronomersmith Quote
I didn't know that the AF system of the camera did that on a manual lens - I was just assuming it "thought" it sensed a good focus.
Well that is sort of what it does. The camera AF system is active and when an area becomes in focus it lights up a dot and turns on the AF confirm light (at least in my cameras). The camera does not care how the in focus situation came to be, either by you manually focusing or by the AF system moving the focusing optics. Makes no difference, in focus is in focus. I am not familiar with your camera, never owned that one, so my comments should be considered generic, but that is how it works on newer cameras. Although on my cameras (k-5IIs and k-3) only the center point AF light will work with manual lenses.
11-19-2014, 03:18 PM   #6
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QuoteOriginally posted by Astronomersmith Quote
Can't focus
What camera are you using? If you have live view - and possibly even focus peak - it is worth trying that out too.

When you use live view and manual lenses you will be using the very image itself formed by the lens in the sensor plane to determine proper focus. As suggested by jatrax, you should use a tripod in order to eliminate other sources of error. With a stable tripod you may try to use some 6-10X magnification of your live view image.

My own experiences with some vintage lenses from the 80'ies and 90'ies is that after many years of use (and sometimes some rough beatings too) they may have gotten considerably out of collimation, so you may have a lens problem rather than anything else......
11-19-2014, 03:28 PM   #7
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My guess is that this is the lens, based on your description: Pentax-A 70-200mm F4 Reviews - Non-SMC Pentax Zoom Lenses - Pentax Lens Reviews & Lens Database If that's your lens, don't worry too much. I have one and it's not very good. Avoid using it at f4, and flare is bad.

The red square in the viewfinder means that's the active AF focus point. Manual focus lenses only use that center point so just ignore that. In the line below the image, there's a green hexagon that will light up, telling you that the sensors have detected focus at that center point. If the AF-MF switch (front of camera) is in AF, the camera by default won't fire the shutter until that hexagon is lit. In the MF position, you can shoot whenever you want.

One test I like: shooting a flat plane at an angle. Somewhere in there is a point of exact focus. Once you get the right setup (a tripod is best here), you can figure out if the lens is focusing in front of or behind where you intend.
11-19-2014, 03:46 PM   #8
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QuoteOriginally posted by jatrax Quote
If you get a chance post back with the full lens model description. Pentax has a long history and it is easy to confuse one model with another unless you describe it precisely. Just one letter off can be a completely different lens.

I still do not find a 70-200 in Pentax brand but they did make a 70-210 such as this one: SMC Pentax-A 70-210mm F4 Reviews - A Zoom Lenses - Pentax Lens Reviews & Lens Database which was fairly highly regarded. The 'cheap' kit lenses were later in the F and FA series and those are AF lenses. Still, zooms of that age were not optically that great, modern zooms are almost always better as opposed to prime lenses where the older ones seem to hold up much better compared to modern ones.

If it is a push / pull design in my experience the focus is much looser than say a prime lens of the same age. I used to have a 75-150mm zoom and the focus was quite smooth and maybe a touch too loose. So that is not for sure a sign that anything is wrong.


Well that is sort of what it does. The camera AF system is active and when an area becomes in focus it lights up a dot and turns on the AF confirm light (at least in my cameras). The camera does not care how the in focus situation came to be, either by you manually focusing or by the AF system moving the focusing optics. Makes no difference, in focus is in focus. I am not familiar with your camera, never owned that one, so my comments should be considered generic, but that is how it works on newer cameras. Although on my cameras (k-5IIs and k-3) only the center point AF light will work with manual lenses.
jatrax, I apparently have it wrong again. I won't be able to post again until tomorrow probably, and I'll do my best to bring the lens information so I can get it right! Sorry. Now that I think about it, it probably is an 80-200, but don't hold me to that! <haha> Until I can confirm it.

Scott

---------- Post added 11-19-14 at 04:51 PM ----------

QuoteOriginally posted by Stone G. Quote
What camera are you using? If you have live view - and possibly even focus peak - it is worth trying that out too.

When you use live view and manual lenses you will be using the very image itself formed by the lens in the sensor plane to determine proper focus. As suggested by jatrax, you should use a tripod in order to eliminate other sources of error. With a stable tripod you may try to use some 6-10X magnification of your live view image.

My own experiences with some vintage lenses from the 80'ies and 90'ies is that after many years of use (and sometimes some rough beatings too) they may have gotten considerably out of collimation, so you may have a lens problem rather than anything else......
Stone G
I think I included it in my original post, but maybe not....I'm using a Pentax *ist DS.

Just1MoreDave
I'm very familiar with my Ds and really like it a lot. I'm thinking of getting a newer, "better?" one, but that may be a while. I know exactly what you are describing with the hexagon being lit when focus is achieved. It always flashes when the little red square indicates the focus point. I rack the focus past that point, then come back to it the other way and "wiggle" back and forth. That makes the focus light come on and off, so I'm pretty sure that I am getting the focus that the camera is suggesting.

BTW, I appreciate all the responses! Wow! I'm brand new to this forum, but I can already tell from this thread, and all the other information I've read on here, that this is a great resource of information! Thanks.

Scott

11-19-2014, 04:00 PM   #9
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Maybe this one then: SMC Pentax-A 80-200mm F4.7-5.6 Reviews - A Zoom Lenses - Pentax Lens Reviews & Lens Database Which by the ratings did not have a good reputation. And it looks sort of like a cross between the 'A' series and the 'F' series so maybe was a transitional model at least for styling.

And if this one does not work out, there are lots of very inexpensive lenses on the market if you are OK with manual focus. Just ask for recommendations or browse the lens database. There are also duds out there so do your research before buying.

Here is a real gem and one of my favorites: SMC Pentax-F 70-210mm F4-5.6 Reviews - F Zoom Lenses - Pentax Lens Reviews & Lens Database Often available for $50-75 and it is fully auto focus.
11-20-2014, 07:53 AM   #10
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I think that A series 80-200mm was identical to the F series version, just without the AF functions. My guess would be that it was intended for the MZ-M along with the similarly styled but horrible 35-80mm. The F versions were bundled with most of the double-digit MZ series cameras.

I found the F 80-200mm wasn't bad at all, after buying one for 10 with some mould on the back of the front element. I unscrewed it, cleaned it, reassembled, and used it for a few months before giving it to my brother along with my old K-m and 18-55mm.
11-20-2014, 08:23 AM   #11
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Everyone: Thanks for the help. I've messed this question up from the beginning. I'm sorry. This time, I'm posting the information and a picture (if I can get it to work here) of the lens I have been talking about.
It is: SMC Pentax-A 1:4.7 - 5.6 80-200mm. It has these numbers on the other side: 4785102.

Scott

---------- Post added 11-20-14 at 09:27 AM ----------

QuoteOriginally posted by jatrax Quote
Maybe this one then: SMC Pentax-A 80-200mm F4.7-5.6 Reviews - A Zoom Lenses - Pentax Lens Reviews & Lens Database Which by the ratings did not have a good reputation. And it looks sort of like a cross between the 'A' series and the 'F' series so maybe was a transitional model at least for styling.

And if this one does not work out, there are lots of very inexpensive lenses on the market if you are OK with manual focus. Just ask for recommendations or browse the lens database. There are also duds out there so do your research before buying.

Here is a real gem and one of my favorites: SMC Pentax-F 70-210mm F4-5.6 Reviews - F Zoom Lenses - Pentax Lens Reviews & Lens Database Often available for $50-75 and it is fully auto focus.
============

Jatrax,
That is it. I just tried to upload a picture of my lens. Hopefully it went through, but you guessed correctly! Thanks for your time and effort to help. Also, I apperciate the recommendation of the 70-20....that sounds encouraging! Because, I have been and am very discouraged with the one I have now. I've missed several important moments at family events because of poor focus.
My family says, "oh, its a good picture"...but I know better! It looks terrible because it is not a sharp focus. I guess, like most photographers, amateur and professional, I'm highly critical of my efforts.
Thanks again.

Scott
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11-20-2014, 11:43 AM   #12
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I had one of those and just like Dangermouse, gave it to my brother.

This is an example of the test I was explaining. I went the extra mile here, using my *ist DS and my not very good 70-200 zoom. (Actually it looks better than I remembered.) I have the camera on a tripod, put the tape on the wall, focus on the tape, shoot wide open, then see if the zone of focus is where I focused.



You may have to adjust distance and angles to get a shot where the focus plane is obvious. Refocus a few times while you have the same setup to get a larger sample to work with. This should tell you if the focus screen is showing you the correct focus.

Your lens is not great for manual focus because it doesn't let in a lot of light and isn't too sharp. That makes seeing the point of focus harder. If you do the above test, the resulting image will probably show a much more obvious focus plane than you saw in the viewfinder. The DA 18-55 will be a lot easier to focus than the A 80-200 lens.

You could follow this test with shooting a brick wall straight on, at a good distance, like 30 feet. If your sensor is parallel and perpendicular to the wall, all four corners of your shot should look the same. Alignment is tricky - maybe use a level and measure. The A 80-200 has a lot of internal plastic and may be prone to elements shifting around out of alignment.
11-24-2014, 09:02 AM   #13
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I got out and experimented a little this weekend. And I've pretty much decided that my cheap zoom lens is a piece of.....junk. Not what I wanted to call it, but, it'll have to suffice.
I did learn a good bit about the focus indicators, (little red box) and the in focus hexagon/pentagon, shaped icon on the bottom of the viewfinder. Still...the focus was SO hard to get, and on a bright, sunny day, all different f/ratios tried, the image looked just, " eh " at best. Soft, not sharp at all, just really disappointing. No wonder I couldn't get any good photos at night/low light situations with this lens!
Thanks to everybody for all the helpful suggestions and guidance!

Now...to decide if I want to get another lens for my old DS, or splurge, and get a new camera with lens combo? I've been drooling at the K-50 2 lens kit...but for me, even $596 is A LOT of money! I may opt to keep using old faithful *ist DS and get a better used lens for it.

Scott
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