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05-20-2016, 10:07 AM   #1
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K-3 and DA*300 at airshow


Last week I had to opportunity to go to an airshow near Paris.

While some of my pictures are really stunning with lot of details and contrast, others are more soft.
If you look at the picture of this (amazing) spitfire, you will see what I'am talking about.

I know that my lense (DA*300mm f/4) si capable of better performance, so I wonder what is cause of this softness. Is it bad focussing? Mirror Shake? IBIS side effect? Motion Blur?

This picture was taken in RAW at 1/2000, F4, 100 ISO, hand handeld and with shake reduction ON.

Any help is welcome to avoid this kind of problem next time

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05-20-2016, 10:29 AM   #2
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If you were following the plane, which I think were, you should probably disable SR. SR will try to correct your panning movement, and thus works against you... Don't know how much it could affect the image though...
05-20-2016, 10:42 AM   #3
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Thanks for the answer. I will try to turn off the SR next time to see if there are improvements.

With SR off, what is the lowest shutter speed that I can use (with 300mm on aps-c)?
05-20-2016, 11:01 AM   #4
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Generally 1/125 was considered fast enough to mitigate motion blur. 1/250 is safer. I don't think in a bright setting you'll have problems turning off SR.

05-20-2016, 11:11 AM   #5
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The general rule for hand holding is 1 / shutter speed (x 1.5 crop) So 1/450+. That being said it depends on what you're shooting, the lighting, your general steadiness, whether you have something to lean against, your breathing.. etc.
05-20-2016, 11:22 AM   #6
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When shooting props another reason to stay within 1/250 range if possible is you get propeller-blur, which adds more "action" to the picture. 1/2000 will freeze everything and make it look like your subject is hanging, or a speeding race car appearing to be parked.
05-20-2016, 11:27 AM   #7
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The left side of the image looks sharper than the right leading me to believe there was slight front focus.

Also there is no need to shoot this wide open. Stop down to at least 5.6 for a slight increase in sharpness and depth of field.
05-20-2016, 11:43 AM   #8
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I'll put my bets in motion blur.

Although I never done airshows before, the image apears to me, it was "shaked" by the SR System. I can see motion blur in the horizontal axys, so it might tried to correct for the panning.

Try turn it of next time.

I also had some issues with it sometimes. But mine are the K5II tough, not smartest SR of the line up.

05-20-2016, 12:27 PM   #9
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The K3II is supposed to deal with panning blur better than previous models, but I still see a difference. I need to remember to turn SR back off when I'm not using it myself.
05-20-2016, 12:48 PM   #10

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Your camera just "guessed" wrong.

You can recreate the same issue if you try to focus on a flat (as in muted) color wall all the same medium shade. In this case the olive drap swath and smooth sheet metal of the plane did not provide enough for the PDAF to truly lock on a target. PDAF likes hard edges, not soft smooth surfaces.

I can counter this to some degree by feathering the half press (of back af button). Some times it doesn't hurt to focus on several parts of the plane a couple times just to "educate" the lens. I will also try to place the spot focus on a decal or canopy frame. Chances are you are cropping an air show photo anyway, so find a good focus point first and don't worry so much about composition.

The K3 is better than earlier generations of Pentax DSLRs but its AF is still quirky.

Last edited by nomadkng; 05-20-2016 at 12:53 PM.
05-20-2016, 12:54 PM   #11
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F8 would do just fine

05-20-2016, 01:00 PM   #12
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QuoteOriginally posted by nomadkng Quote
smooth sheet metal of the plane did not provide enough for the PDAF to truly lock on a target
The overcast day certainly did not help the camera's task.
05-20-2016, 02:02 PM   #13
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Many thanks for your advices. Just another technical question.
I had some difficulties with the auto focus. I used single mode (not continues) with center spot point. Results were ok but I miss some shoots because autofocus system was hunting. I also tried the continues mode with 9 points but this was not accurate. I had a lot badly miss-focused shoots.
Which mode and parameters do you use for this kind of situation?

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