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03-15-2010, 03:20 PM   #1
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Seem to be having trouble with focus

Ive been getting familiar with my K7 for a few weeks now and i guess my biggest question so far is " why are the majority of my pictures not that sharp when enlarged?"

Here are examples. They look ok until they are enlarged then they reveal the slight blur. Im always using the lowest Aperture to gather the most light for the most part. Could this have something to do with it? I also only use manual focus on my DA16*-50 and DA 55-300mm lenses for the majority of the time. I had read that some say not to trust the AF. I guess i just like manually controlling the lens too.

Maybe the shutter is too slow? Its really hard to tell how focused the image is in the viewfinder sometimes but the Focus indicator is usually flashing when i find i have it focused by my eye. Thanks for taking a look. These have both been cropped too.

This one was takin using 1/125, 800 iso, 300mm, 6.3f





and this one 1/250, 800, 5.8, 300mm



03-15-2010, 03:30 PM   #2
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You need to shoot animals or birds at higher shutter speeds than 1/125s. The problem is, they move, trees move and 1/125s isn't going to stop the movement or the bird/squirrels. I use at least 1/500s. And that depends on how windy it is outside or how active the animal/bird is. One twitch from them and it's a blurred shot.
03-15-2010, 03:37 PM   #3
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In addition to what Photolady said, the longer the focal length the more movement on your part is exaggerated, SR can only do so much.
The focus indicator is the red square and all that is doing is giving you a rough idea where the camera is trying to focus. Focus confirmation is via the solid green hexagon which flashes when the camera is moving in and out of focus (maybe because you are moving or the subject is moving). It will stay illuminated when you are in focus.
03-15-2010, 07:29 PM   #4
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QuoteOriginally posted by jas Quote
Ive been getting familiar with my K7 for a few weeks now and i guess my biggest question so far is " why are the majority of my pictures not that sharp when enlarged?"
With the turkey shot, it looks like the plane of focus falls a bit short of the turkey's head. Leaves on the ground in front of the turkey look reasonably sharp. With the exposure numbers you gave, obviously there wasn't much chance to lower shutter speed, stop down or or raise ISO without causing some other potential issue. If you can, focus-bracket: take a shot, refocus, take another, etc. Some of what you see may just be from viewing 100% on a computer monitor. I bet this shot would look fine printed even up to 8x12.

The squirrel shot does not seem to have anything in sharp focus; possibly the tree on the right. You were closer to the recommended shutter speed. I can't come up with any brilliant suggestions here.

03-15-2010, 10:44 PM   #5
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You mentioned that you often shoot wide open. This can cause "softness" with most lenses. Also, shooting at the extremities of your lens' focal length will exaggerate softness. The pictures you're showing as examples both suffer from these two issues.

This, in addition to the reduced effectiveness of shake reduction at long focal lengths, can be responsible for the lack of sharpness. Also, try updating the firmware of your camera if you haven't already.

Since the EXIF data was stripped by Flickr (God I hate that), I can't tell if Shake Reduction was even used for your pictures. If you don't wait for the green hand icon to light up (takes half a second after you obtain focus), then Shake Reduction isn't even on yet.

One more thought, how much of a crop are you showing us here? Are you taking like 1/10 of the total image?
03-16-2010, 02:52 AM   #6
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One rule for shutter speed is: 1/FL -- that is, with a 100mm lens, you shoot at 1/100 sec or faster. And that's for stationary targets. SR might give you an f-stop leeway in one direction, but living moving targets take away two f-stops the other way. As photolady said, at 300mm you should shoot 1/500 sec or faster (unless your subject is dead). Faster is better.

Besides wide apertures and extreme zooms, the critters in these pictures aren't well lit; the turkey isn't too contrasty vs its background; and the squirrel is a pretty small target. It's hard to lock-on focus there. Try switching the AF to center (or SEL a focus point); and as mentioned, you have to wait for the Green Hex before SR works. And consider using Catch-In-Focus (see recent threads about that).

There's a reason birders and other shooters of distant critters spend big bucks on fast glass: they let in more light. Alas, such lenses ain't cheap, nor lightweight. Your 55-300 is only f/5.8 at best at 300mm. You obviously need the DA* 300/4 or the Sigma 300/2.8 EX. Right. Or sneak in closer.
03-16-2010, 06:41 AM   #7
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Thank you every one for responding. And right off the bat there are a few obvious things i had forgotten about that make sense now. The Shutter speed in relation to the zoom rule is one and the i also completely forgot about the green hex. Also the IS must not have been working if the hex wasnt showing up. At full zoom and hendheld i can see that it could have helped.

The pics were cropped about 10 percent. And its been quite overcast the past few weeks too. Thank you for the refresher.
03-16-2010, 08:35 AM   #8
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QuoteOriginally posted by jas Quote
Also the IS must not have been working if the hex wasnt showing up. At full zoom and hendheld i can see that it could have helped.
There is a little hand symbol in the viewfinder for SR. After focus is achieved, you need to wait till that comes on before taking the picture if you have SR enabled. If not, the result can be worse than without SR as the sensor is moving. I often forget and therefore have SR off by default and only use it when I think I need it; this makes me more aware of the fact that I have to check it.

QuoteOriginally posted by Damn Brit Quote
The focus indicator is the red square and all that is doing is giving you a rough idea where the camera is trying to focus. Focus confirmation is via the solid green hexagon which flashes when the camera is moving in and out of focus (maybe because you are moving or the subject is moving). It will stay illuminated when you are in focus.
I use the focus indicator as focus confirmation. It briefly flashes when focus is achieved and that should be sufficient (K10D). The times that I verified it against the green hex, it shows up at the same time.

03-16-2010, 09:00 AM   #9
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QuoteOriginally posted by RioRico Quote
One rule for shutter speed is: 1/FL -- that is, with a 100mm lens, you shoot at 1/100 sec or faster. And that's for stationary targets.
The rule of thumb applies to 35mm equivalent lengths, so the recommendation for a 100mm lens on an APS-C camera would be 1/150s. I know you know this RioRico, because you said 1/500sfor 300mm focal length, but I'm not sure the OP got it.
03-16-2010, 10:39 AM   #10
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QuoteOriginally posted by audiobomber Quote
The rule of thumb applies to 35mm equivalent lengths, so the recommendation for a 100mm lens on an APS-C camera would be 1/150s. I know you know this RioRico, because you said 1/500sfor 300mm focal length, but I'm not sure the OP got it.
I ran that off from memory, and from my 35/HF days of using the Olympus Pen-FT with a frame close to APS-C size. But now I wonder.

So I gargle FOCAL LENGTH SHUTTER SPEED RULE and find this MINIMUM SHUTTER SPEED page which (among other things) cites Ansel Adams' research showing that with a 50mm lens on a 35mm film camera, the minimum shutter needed for sharpest handheld photos is 1/250 sec!!. That is 1/(FL*5)! Take the reciprocal, add TWO f-stops.

This page then renders some math using factors of lens focal length (rather than angle of view) and maximum resolution of sensor in lines per mm. I just got up, I'm on my first cup of coffee, my algebra circuit isn't kicking in; I can't yet see how to put this in effect with current lenses and sensors -- the page was written in 2004, when 4mpx was hot. But it LOOKS like the rule for APS-C should be something like 1/(FL*6) sec for sharpest shots!!

In other words: Convert FL to 35/MM equivalent using crop factor. Take reciprocal. Divide by at least 4 (two f-stops, maybe more). So for a 100mm lens it's 100x1.5= 150; 1/150 / 4= 1/600. Fudge factor= 1/750 sec. That's without SR. If SR gives you back 2-3 stops, then we're right back at 1/FL. Or are we? Lemme pour some more coffee and think about it.

EDIT: I search a little more and see (scan) some MINIMUM SHUTTER SPEED discussions on these forums, which mainly revolve around calculations and whether to apply the crop factor. What's missing is: experimentation. Those serious about ultimate crispness (NONE DARE CALL IT PIXEL-PEEPING) should test their cameras, their lenses, themselves. Factors: lens angle-of-view and maybe length and weight; sensor lines-per-mm resolution; human twitchiness. Test yourself with and without coffee, milk (lactic acid degrades vision, as I learnt in my US Army pistol chambionship days), alcohol, food, fatigue, excitement, etc.

Last edited by RioRico; 03-16-2010 at 11:06 AM. Reason: addendum
03-16-2010, 10:58 AM   #11
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QuoteOriginally posted by RioRico Quote
So I gargle FOCAL LENGTH SHUTTER SPEED RULE and find this MINIMUM SHUTTER SPEED page which (among other things) cites Ansel Adams' research showing that with a 50mm lens on a 35mm film camera, the minimum shutter needed for sharpest handheld photos is 1/250 sec!!. That is 1/(FL*5)! Take the reciprocal, add TWO f-stops.
I'm sure there are other theories, and faster shutter speeds are better (if you can get them), but the commonly referenced rule is 1/s, normalized for 35mm film, therefore 1/100s for a 100mm lens on a full frame, and 1/150 on Pentax sized APS-C.
03-16-2010, 11:15 AM   #12
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QuoteOriginally posted by audiobomber Quote
I'm sure there are other theories, and faster shutter speeds are better (if you can get them), but the commonly referenced rule is 1/s, normalized for 35mm film, therefore 1/100s for a 100mm lens on a full frame, and 1/150 on Pentax sized APS-C.
In prior discussions on these forums, noted savants disagree as to whether to 'normalize' by including the crop factor. And is SR factored in? My first link above shows gargle hits on many other discussions and lessons, with no agreement. So I'd humbly follow in Ansel's footsteps and test, test, test.

Oh, it's the old theoreticians vs experimentalists conflict. John McPhee in THE CURVE OF BINDING ENERGY quotes nuclear physics theorist Ted Taylor as distinguishing the two. Experimenters are conservative, arrogant, brusque. Theorists are liberal, kind, fuzzy. That's in nuclear physics, at least in the 1940's and 50's. What are we now?
03-16-2010, 11:48 AM   #13
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Ofcourse you need to factor in the crop and SR does nothing for movement

If you are in doubt about the need to factor in the crop, use a compact superzoom with a 12mm lens that's ev to 700mm or whatever and try shooting at the full focallength and 1/20th second ...... you'll see pretty quickly that the ROT applies to the crop factor.
03-16-2010, 12:10 PM   #14
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QuoteOriginally posted by RioRico Quote
In prior discussions on these forums, noted savants disagree as to whether to 'normalize' by including the crop factor.
If one accepts that the rule of thumb is one divided by the focal length of the lens, then one must consider the crop factor. To ignore the effect of crop factor makes no sense, because the shutter speed rule is based on FOV. If OTOH, you are disputing that 1/FL is the commonly accepted rule of thumb, then I'd say you just want to argue.

QuoteOriginally posted by RioRico Quote
And is SR factored in?
Shake reduction is not considered in the rule of thumb.
03-16-2010, 01:34 PM   #15
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QuoteOriginally posted by audiobomber Quote
If one accepts that the rule of thumb is one divided by the focal length of the lens, then one must consider the crop factor. To ignore the effect of crop factor makes no sense, because the shutter speed rule is based on FOV. If OTOH, you are disputing that 1/FL is the commonly accepted rule of thumb, then I'd say you just want to argue.
Sometime I just like to argue, but I'm not arguing this, and I'm not even asking if the ROT is 'right' or 'close enough' or whatever, or whether crop factor (CF) should or must be applied. I'm saying that we need to test ourselves to establish our own ROTs to suit our own tastes, needs, abilities, etc.

In the MINIMUM SHUTTER SPEED article I cited above, the author noted that maximum sharpness is based on FOV and shutter speed and sensor resolution and human shakiness. So the ROT would differ on APS-C sensors of 6mpx, 10mpx, 15mpx, and at higher ISO with more noise; you can't just apply 1/(FL*CF) and get the same sharpness, if I understand that author correctly.

That author cites Ansel Adams' THE CAMERA. Here is what Adams says about full-frame 35mm (where 'normal' lens is 50mm):
"The general rule to observe whenever the camera is hand-held is to use as fast a shutter speed as you can, consistent with the requirements of exposure and depth of field. Tests I conducted... indicated that, using a normal lens with a hand-held camera, the slowest shutter speed that ensured maximum sharpness was 1/250 second. I found that even with firm body support image sharpness was noticeably degraded at 1/125 second, a speed that many photographers consider safe for hand-holding a camera with normal lens. With a lens of longer than normal focal length, even shorter exposure times will be required: 1/500 second for a 100mm lens and 1/1000 second with longer lenses, as a guide."
As with vehicle fuel efficiency, your mileage may vary. We all have different levels of comfort re: sharpness, immediacy, drama, etc. We all twitch differently, and at different times. We might devise a baseline ROT for grab shots; go two stops slower for scenery, two stops faster for dramatic action, etc. One ROT does NOT fit all.
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