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08-14-2008, 03:48 PM   #16
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Thanks for your response.
Sorry, but I don't understand what EXIF is (or how to include it).
Here's a couple of Photobucket images (first @ 75mm, second @300mm both 1/90sec@F4.5 ISO 800):-


Both taken using a monopod.


Last edited by G-CPTN; 08-14-2008 at 03:54 PM.
08-14-2008, 04:05 PM   #17
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75mm and 300mm again, 1/60sec@F4.5 ISO800:-

08-15-2008, 05:05 AM   #18
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Well, if you use Firefox, google for the "exif viewer addon" - when you right click on images you'll have the option to "View Image Exif Data" which often gives you lots of interesting information/settings about the photo.

When I look at the EXIF for these images, I see that all of them say 0mm focal length. If these are not FA lenses, I think you need to turn the camera off, mount the lens and turn it on. The camera will then prompt you to enter focal length. With a zoom, it's probably best to enter the shortest focal length (you don't want to over shake reduce images at the shorter focal length). For shots like this, though, I would have turned it off and set the focal length to 300 for the long shots. I think 1/90th of a second is way to slow for a 300mm lens (450mm equiv!).

Alternately, turn shake reduction off and put your camera on a wall, bench, beanbag, etc and take a photo using the 2 second mirror lockup.

Finally, when I look at these pictures, it actually looks like stuff in the forground is what's in focus. Take the first image (cars with wall on the left), to me it's the wall and bush on the left that are in focus, not the cars in the center of the image. In the second picture, it looks like the grass right behind the pile of mushroom stuff is what's in focus, but the pile-o-stuff might be the intended target...
08-15-2008, 07:57 AM   #19
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I've tried various things today using the standard lens.
Reviewing the apertures used by my various photos (33 in total so far - from new, out-of-the-box) those taken with the bundled lens are typically f9.5 whilst the Sigma shots are f4.5 (thus the depth of field is greater for the bundled lens, quite apart from the 'telephoto' effect @1.5x300mm . . .

I'm going to take a series of shots using the bundled AF lens but using aperture priority @ f 5.6 (the widest aperture at 1.5x55mm).

I'm 'seeing' from images taken that the sharpness is definitely foreground, despite using distant objects for autofocus, so I'm looking for a long view with objects positioned at intervals that I can use for focus points, as I'm beginning to suspect the basic focussing of the camera, rather than a specific mismatch with the manual lens . . .

Is it 'unknown' for a fault like this 'out of the box'?
Although I bought off eBay, the camera (and lens) were sealed and unused.

08-15-2008, 08:04 AM   #20
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Well, my K20D was a focus dud out of the box so it's not unheard of.

There are lots of focus tests floating around. I started off with just using a tape measure and it was just as 'educational' as setting up a formal test.

Remember, when you do your tests, take several photos (5 or 6) and move the focus ring to either extreme for each test. You'll get some variability between shots, but if you pattern is always front or back focus, you might have a problem.
08-15-2008, 08:39 AM   #21
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So in case you haven't figured it out, the EXIF *is* intact for the images you posted. EXIF that's just the name of block of information the camera records about the settings used. If you are able to look at the images in your favorite viewer/browser and somehow find out the camera settings used, you're looking at EXIF, whether the browser calls it that or not.

Anyhow, first thing is, I'm confused about the lens. You said it is a "manual" lens, and indeed, it seems to not record the focal length used. But it does record an aperture of f/4.5. So does this lens have an "A" position on its aperture ring, and you really are using f/4.5 when shooting, or is it just for some reason always reporting f/4.5? Is the lens even actually capable of f/4.5 at the long end? If that is its max aperture, I also wouldn't be expecting maximum sharpness - although the posted examples are indeed pretty terrible at 300mm.

QuoteQuote:
I'm 'seeing' from images taken that the sharpness is definitely foreground, despite using distant objects for autofocus, so I'm looking for a long view with objects positioned at intervals that I can use for focus points, as I'm beginning to suspect the basic focussing of the camera, rather than a specific mismatch with the manual lens . . .
Still confused - I thought you said it was a manual focus lens?

Anyhow, if you are going to do focus tests, you absolutely need to download a well-designed focus test chart like the one at focustestchart.com. That's the only way to really reliably control what an AF system is actually focusing on, and it's also a very handy chart for testing MF.

BTW, it could well be the lens is defective and simply won't go to infinity at the long end.

Also, you didn't say if you were entering to correct focal length to the SR system when you changed zoom, but that's important in order for it to function properly.

But consider - you're shooting 300mm lens at 1/90 second whereas normally you'd expect to need at least 1/450 to have a chance at a sharp image. That's expecting an awful lot of SR, or of a monopod. Chances are pretty good that this is camera shake, plain and simple, and you just need to use a tripod or get a faster shutter speed.
08-15-2008, 09:14 AM   #22
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Lots of confusion.
The bundled 18-55 mm lens is autofocus and about half (now) of my photos have been with that lens. At first these seemed to be OK, but, the aperture (f9.5) was 'smaller' and, the focal length being shorter, the depth of field would be greater, however, I have some shots (not shared here) that have the foreground distinctly sharper than the distant object that I was using for autofocus.
I've tried (just now) to repeat this, but inconclusively.

The photos that you've seen here were taken using the manual focus Sigma KA 75-300 APO lens (f4.5) set on the 'A' setting focussed manually on the MF setting and the Shake Reduction turned off.

I cannot print out a test-card as my printer is misbehaving, thus I decided to use a (long) street view with vehicles parked along it and using receding focus points (autofocus) using the bundled lens to see if I could 'prove' the problem to lie with the basic equipment rather than with using a manual lens. I have a wide range of lenses (both prime and zoom), but it seemed a complication trying yet another lens before 'proving' with the bundled lens.

I've not had any problems with the 75-300 lens on Super As, though I haven't seen my latest efforts yet.

As the majority of the intended use will be 'infinity' work (airshows) I hesitate to use macro techniques to quantify any error.

It's late afternoon here, and I'm tired (mentally) so I'll probably wait until another day before continuing testing. I an't say that I'm particularly impressed with any of the 38 photos that I've taken so far. If I hadn't bought from eBay I'd be taking it back to the shop . . .

Is there a 'viewer' (other than Microsoft Windows Photo Gallery) that will display the full resolution of the image (ie 6Mp). I suspect that MWPG reduces the pixel count . . .
08-15-2008, 10:30 AM   #23
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While I haven't used the particular Sigma you are I have the 70-300 autofocus which is probably similar. Its not very sharp at 300 at all and works best between f8 and f11. It's quite heavy and wouldn't even think of trying to take a picture at 1/90 without it being on a tripod or monopod. I have had camera shake issues even at 1/250 with the zoom extended. If you are manually focusing did you adjust the diopter? I have the K10D and the autofocus point can be selected. Are your settings right? It is fairly easy to inadvertantly change a setting. I have done it.
You mentioned shooting airshows. Get a good monopod or tripod. Shooting an airshow with a manual lens isn't easy.

08-15-2008, 12:21 PM   #24
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All (of my) photos posted here were taken using a monopod.

When using long focal length (ie 300 or 400mm) lenses with 35mm film cameras for aerial shots I use 400ASA film, it's usually a bright, sunny day, and I use a rifle-butt and a monopod (combined).

I've taken a few photos using a Sigma KA 400mm f5.6 prime lens and the furthest distance is not in focus, despite use of Shake Reduction (set to 400mm). Again I was using a monopod (and leaning with my back against a substantial tree.
Here's one, where the manual focus was 'sharp' on the blue car in the distance:-


Unfortunately, the field of view of the 1.5x400 doesn't allow me to include the intermediate focus points (the white bay windows on the left), so I'll spare you the shots set at closer focus points. Suffice to say that they seem 'reasonably' accurate up to the furthest window, it's beyond that where the divergence occurs.

I intend finding a better (!) subject (I can think of a surface carpark on a slope) and will do a comparison of the bundled lens and the two Sigmas.

I might even use my 50mm f1.4 lens too.
08-15-2008, 12:28 PM   #25
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OK, I'm less confused.

I understand the hesitation to use a tst chart to test infinity focus. I'd start by simply focusing to infinity - not even looking through the viewfinder - and doing the street test you mentioned.

QuoteOriginally posted by G-CPTN Quote
I have some shots (not shared here) that have the foreground distinctly sharper than the distant object that I was using for autofocus.
I've tried (just now) to repeat this, but inconclusively.
I'm going to guess that on the problem shots, regardless of what *you* were using the AF, the *camera* was choosing something close. An actual front focusing problem would normally show discrepancies of inches or at most feet when dealing with distance objects - sounds like you are describing something more drastic. And that could really only be a matter of the camera just focusing on soemthing other than what you thought it focused on.

QuoteQuote:
The photos that you've seen here were taken using the manual focus Sigma KA 75-300 APO lens (f4.5) set on the 'A' setting focussed manually on the MF setting and the Shake Reduction turned off.
OK, then I'm still going with a combination of general lens softness - you're using the extremes of both focal length and aperture - and camera shake. But it would indeed be useful to do the street test you mention. Just set the lens at infinity, point down the street, and see if *anything* is in focus.

QuoteQuote:
Is there a 'viewer' (other than Microsoft Windows Photo Gallery) that will display the full resolution of the image (ie 6Mp). I suspect that MWPG reduces the pixel count . . .
Well, if the image fits on your screen, than of course it is reduces the pixel count. But I would imagine *any* viewer would display it full resolution - you'd of course be seeing only a small portion of it at once. Are you suspecting that Picture Gallery is blowing it up that big but resampling the image anyhow? Seems that would be much more work for it than to simply display it pixel for pixel - can't imagine why it might do something like that.
08-15-2008, 12:34 PM   #26
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My previous post and yours with the new picture seems to have crossed; I was not replying based on the most recent info.

If the blue cars was in focus in the viewfinder and the closer wall was not, then I'd say your focus screen is probably mis-seated, as it sure looks the other way around here. If both looked in focus, then I'd say maybe the issue of too great a DOF in the viewfinder is the problem, even though you're obviously at smaller than f/2.8. Maybe the smaller DOF at 400mm comes into play?

It would be interesting to shoot another seen like this with less confusion around the intended subject, to see if the focus confirmation light agrees with the viewfinder or with the actual image.
08-15-2008, 02:51 PM   #27
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Thanks for the replies.
My 'depression' has eased, however I'm 'regretting' not spending a few pounds more and buying from the local camera shop (then I could 'return' it instead of having to deal direct with Pentax UK). The local shop staff are friendly (I've bought lots of secondhand film equipment from them in the past) but I don't feel that I can involve them when I didn't buy the camera from them (especially as they have a brand new K100D Super at a sale price . . . ). I even tried it out after I'd bought on eBay but before mine arrived.
I repeat that the one from eBay arrived sealed and unopened.
08-15-2008, 03:04 PM   #28
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Yeah, that's one reason I prefer to buy locally on an item of this kind of complexity. The savings from ordering online are generally not worth pain if anything goes wrong.

Anyhow, if it *is* a mis-aligned focus screen, there is always the possibility you could fix it yourself - it *might* just be matter of removing it and putting it back in. The K100D is not designed to take interchangeable screens, but I gather it *is* possible to remove it and replace it - people have managed to installed the Katz-Eye themselves. So you might look into that, if you aren't worried about voiding your warranty.
08-16-2008, 11:54 AM   #29
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QuoteOriginally posted by G-CPTN Quote
Thanks for your response.
Sorry, but I don't understand what EXIF is (or how to include it).
Here's a couple of Photobucket images (first @ 75mm, second @300mm both 1/90sec@F4.5 ISO 800):-


Both taken using a monopod.

Well before you jump to any conclusion whatsoever, would you mind if you can redo the test with a tripod, at F7.1 and 2 s delay. A consumer zoom wide wide open at the tele end is the weakest link and you have not ensured camera shake be absolutely eliminated at all. Also you are wrong in thinking that a consumer zoom has the same degreee of sharpness for 75mm and 300mm. You are lucky to have the same degree of sharpness 75mm to 150mm not to mention 300mm.
The new test should save you a lot of aggravation


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08-16-2008, 04:57 PM   #30
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Somebody mentioned the diopter earlier and I want to repeat it. There were two clicks on mine that looked almost the same and with the one I picked after installing the KatzEye I still didn't feel the manual focus was "close enough" so I tried the other "click" and bingo, the focus points in my photos became much much closer to what I saw in the VF.
I really wonder how many of our manual focusing problems could be alleviated with closer attention to the diopter settings.
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