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06-05-2013, 05:02 AM   #1351
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Rally cross shots

Last weekend attended the ELE 2013 Rally cross. Here are a couple of shots and you can find more overhere https://www.pentaxforums.com/forums/post-your-photos/227029-sports-ele-2013-r...lots-cars.html









06-05-2013, 12:48 PM   #1352
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andre-mz5 thanks for the info. I have read through that test and I read everywhere that the Sigma is the fastest one of the 70-200 available for Pentax (at the moment).

What I am interested in however, is how the Sigma or the Tamron or 60-250 perform on a K5 for example in a parallel series of pictures of a kid or dog running towards you in continuous drive. And how well does the AF-C cope with the faster lens, i.e. are there more corrective steps per time as the lens reacts quicker or is that limited by the body and the deviation from whatever the camera thinks is acceptably sharp? Pure speed of AF on a lens doesn't necessarily mean better or sharper pics IMO as it's still the camera that decides when to release the shutter. To summarise: faster lens, higher in focus success rate? The kit lens 18-55WRII for example couldn't keep up with my 7 year old son running towards me ...
06-05-2013, 04:03 PM   #1353
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QuoteOriginally posted by Samyo Quote
faster lens, higher in focus success rate?
I'd say yes. The HSM even in the older Sigma 70-200 HSM II I have is very fast and makes the lens very nimble and responsive to the camera, compared to for example my DA*300's SDM, the AF of the DA 18-135 and certainly stuff like the screw drive on my DAL 55-300. I feel that the HSM of the Sigma is able to perform AF adjustments more frequently and with more precision, acting on instructions from the camera.

So yes, more keepers - providing one understands the general limitations of AF, and the AF is set appropriately. If you shoot with 11 points active (vs just use centre-spot, for example) then you are asking the camera to do more work and make more decisions about AF. This extra decision maling process may make the AF appear less decisive, and/or lead to a lower keeper rate, as a wider AF pattern may mean AF decisions that make sense to the camera's contrast detection algorithms, but which may not reflect your focus priorities.

You want the camera to focus on the running kid's face, but the camera AF may find the logo on their T-shirt a better, more contrasty AF target, so in the shot the face is blurry but the T-shirt logo is sharp, so you don't get a keeper. Is that a problem of the lens, or the camera, or the user, or all of the above?
06-05-2013, 05:03 PM   #1354
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QuoteOriginally posted by rawr Quote
You want the camera to focus on the running kid's face, but the camera AF may find the logo on their T-shirt a better, more contrasty AF target, so in the shot the face is blurry but the T-shirt logo is sharp, so you don't get a keeper. Is that a problem of the lens, or the camera, or the user, or all of the above?
Imho, the fact the AF points on Pentax cameras are the size of houses makes the problem much worse.

06-05-2013, 05:16 PM   #1355
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QuoteOriginally posted by Samyo Quote
What I am interested in however, is how the Sigma or the Tamron or 60-250 perform on a K5 for example in a parallel series of pictures of a kid or dog running towards you in continuous drive. And how well does the AF-C cope with the faster lens, i.e. are there more corrective steps per time as the lens reacts quicker or is that limited by the body and the deviation from whatever the camera thinks is acceptably sharp? Pure speed of AF on a lens doesn't necessarily mean better or sharper pics IMO as it's still the camera that decides when to release the shutter. To summarise: faster lens, higher in focus success rate? The kit lens 18-55WRII for example couldn't keep up with my 7 year old son running towards me ...
I've got both the Sigma 70-200/F2.8 II (non-IS version) and DA* 60-250/F4 with a K-5 My impression from shooting from the end of the long jump sandpit is that, in a high-speed burst of 4-5 of an athlete leaping off the board and landing in the sand pit (i.e. running straight towards the camera), with AF-C and centre-point AF, is that at least 1 of the shots in the sequence will be OOF.

If it's not raining this afternoon, I'll try to shoot my son jumping up at the local school field. The problem is with the vertical motion of the jump, the shooter needs to do some vertical, and perhaps also horizontal panning, (I shoot on a low tripod), as the jumper can rise above the centre of the frame and AF lock on to the background behind the jumper). I'll see if I can do a few of these to identify outliers.

I usually find with long jump, I have to move back from the edge of the sandpit, so that the proportional change in distance from the jump off point to the landing point is reduced.

Here's an example, shot in March 2013 of my son. Here, for a change, I used the DA 55-300/F4-F5.8. Normally I'd crop and further sharpen them. But here, I've left them all uncropped (to show focus position) with the "Natural Fine" (medium sharp) setting in SilkyPix Pro 4.



1/640s, f/5.6, ISO320-400, 97.5mm FL. AF-C, Centre-point focus.


100% crops showing focus accuracy. Only the 3rd shot in the sequence has really sharp focus. The centre point is the kneecap in the 1st & 2nd shots, although in the 3 shot it was on the edge of the kneecap and may have been the white shorts. In the 4th shot, the centre-point was the "IGA" oval, just about the "407" competitor number. In the 5th shot it was on the sleeve just above "USQ".




Dan.
06-05-2013, 05:39 PM   #1356
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QuoteOriginally posted by FrancisK7 Quote
AF points on Pentax cameras are the size of houses makes the problem much worse
Not necessarily. In my running kid example, if you went with 11 point AF it would be understandable for the AF to lock onto the highest contrast element(s) within the whole 11 point AF matrix. Why wouldn't it do that?

The size of individual AF points may only be an issue if you were to manually select one AF point, or shoot centre-spot, for example, and wanted the camera to hold onto a specific small feature of the target (like a face) and ignore other potential AF targets. Bigger AF sensitivity 'zones' (I dislike the idea of 'AF points') may then mean one AF target feature overlaps with another, hence problems. Smaller AF sensitivity zones may also, of course, help stuff like AF tracking of subject movement work better.
06-05-2013, 05:45 PM   #1357
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QuoteOriginally posted by rawr Quote
The size of individual AF points may only be an issue if you were to manually select one AF point, or shoot centre-spot, for example, and wanted the camera to hold onto a specific small feature of the target (like a face) and ignore other potential AF targets. Bigger AF sensitivity 'zones' (I dislike the idea of 'AF points') may then mean one AF target feature overlaps with another, hence problems.
I shoot center-spot 99.9% of the time and it does miss the mark on regular occasion.
06-05-2013, 05:57 PM   #1358
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QuoteOriginally posted by FrancisK7 Quote
I shoot center-spot 99.9% of the time and it does miss the mark on regular occasion.
Mine does miss the mark from time to time too. But as even super-AF Nikon D4 users are instructed in the D4 manual, (as the linked graphic shows), there are a lot of reasons why even centre-point AF may legitimately struggle which may have little to do with AF point size.

Getting slightly off-track for the thread - sorry.

06-06-2013, 05:00 AM   #1359
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Here's some AF-C centre-point focus tests with a K-5 and the DA* 60-250/F4. 1/800s, f/4, ISO800, EV -0.7 (but +0.5 EV boost applied in PP), 98mm FL for the landscape-orientation shots, and 140mm FL for the portrait-orientation shots.

The shots were taken relatively late in the day, so there's visible noise. Therefore I only used the "Natural" (mild sharpening) setting in SilkyPix Pro 4. I also noticed that the AF-C was a bit hesitant, and the bursts were slower and somewhat erratic. A K-5 II would have been nice here.

The keeper rate was acceptable. Normally I don't include the run-up in long jump, but since this was a test of AF speed when a subject was rapidly coming towards the camera, I've included it, when available. !00% crops are also shown.


























The results with the Sigma 70-200/F2.8 II, from the same session, will be posted tomorrow.

Dan.

Last edited by dosdan; 06-06-2013 at 05:16 AM.
06-06-2013, 06:47 AM   #1360
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QuoteOriginally posted by Samyo Quote
What I am interested in however, is how the Sigma or the Tamron or 60-250 perform on a K5 for example in a parallel series of pictures of a kid or dog running towards you in continuous drive. And how well does the AF-C cope with the faster lens, i.e. are there more corrective steps per time as the lens reacts quicker or is that limited by the body and the deviation from whatever the camera thinks is acceptably sharp? Pure speed of AF on a lens doesn't necessarily mean better or sharper pics IMO as it's still the camera that decides when to release the shutter. To summarise: faster lens, higher in focus success rate? The kit lens 18-55WRII for example couldn't keep up with my 7 year old son running towards me ...
Not all that easy and running toward you is more difficult the running away.

National soccerteam player Dyanne Bito


This is with the DA*300 and the K-5.

You will get a lot off misses in photographing this way, but on the other hand it isn't impossible.
06-07-2013, 01:23 AM   #1361
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As promised, here's the AF-C centre-point focus tests with a K-5 and the Sigma 70-200/F2.8 II. 1/800s, f/4, ISO800, EV -0.7 (but +0.5 EV boost applied in PP), 135mm FL.

The shots were taken relatively late in the day, so there's visible noise. Therefore I only used the "Natural" (mild sharpening) setting in SilkyPix Pro 4.My recollection is that AF-C was not hesitant, prbably due to the bigger aperture when focusing.

I've included an aborted jump as he continued to move forward, albeit more slowly.












































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06-07-2013, 01:51 AM   #1362
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QuoteOriginally posted by dosdan Quote
As promised, here's the AF-C centre-point focus tests with a K-5 and the Sigma 70-200/F2.8 II. 1/800s, f/4, ISO800, EV -0.7 (but +0.5 EV boost applied in PP), 135mm FL.

The shots were taken relatively late in the day, so there's visible noise. Therefore I only used the "Natural" (mild sharpening) setting in SilkyPix Pro 4.My recollection is that AF-C was not hesitant, prbably due to the bigger aperture when focusing.

I've included an aborted jump as he continued to move forward, albeit more slowly.












































Dan.
Thanks for posting the entire burst instead of just cherry picking the top shot to prove some kind of point.

If you have the time and opportunity some day, I'd be interested in seeing the test redone at 200mm f/2.8 in bright daylight.

Regards,
--Anders.
06-07-2013, 02:14 AM   #1363
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QuoteOriginally posted by asp1880 Quote
If you have the time and opportunity some day, I'd be interested in seeing the test redone at 200mm f/2.8 in bright daylight.
Shooting at f/2.8, instead of stopping down to f/4, shouldn't change AF dynamic performance, as AF is done with an open aperture. Of course sharpness, particularly peripheral sharpness, will be affected with a f/2.8 f-stop. But we are comparing sharpness near the centre in these examples.

Instead I was thinking of repeating this earlier in the day, but at say 70mm FL and 200mm FL for both lenses. Probably a straight run towards the camera, so the centre-spot will not change too much.

I think the Sigma came out a little worse in this comparison. This may be due to the FL used. I suspect this may have some effect on AF dynamic performance in a zoom lens, i.e. different FL sweet-spots, related to the inertia of the moving lens focusing mass and the AF adjustment torque.

Dan.

Last edited by dosdan; 06-07-2013 at 02:24 AM.
06-07-2013, 04:16 AM   #1364
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QuoteOriginally posted by dosdan Quote
As promised, here's the AF-C centre-point focus tests with a K-5 and the Sigma 70-200/F2.8 II. 1/800s, f/4, ISO800, EV -0.7 (but +0.5 EV boost applied in PP), 135mm FL.

The shots were taken relatively late in the day, so there's visible noise. Therefore I only used the "Natural" (mild sharpening) setting in SilkyPix Pro 4.My recollection is that AF-C was not hesitant, prbably due to the bigger aperture when focusing.

I've included an aborted jump as he continued to move forward, albeit more slowly.

Dan.
The red shirt is not helping the AF-system. Look at my post above, that shirt off the soccerplayer is an AF-trackingdevice helping getting the job done.

The AF-module in Pentax does not take the color red for preference. I once had a game with fieldhockey where the girls had a red shirt, dark blue skirt and a light blue thing under the skirt. The AF kept pointing to the light blue when possible.
06-07-2013, 04:23 AM   #1365
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QuoteOriginally posted by RonHendriks1966 Quote
The red shirt is not helping the AF-system. Look at my post above, that shirt off the soccerplayer is an AF-trackingdevice helping getting the job done.
Unfortunately we have no control over what sports subject wear. However, In the next tests I run I'll ensure he wears a more varied shirt.

I'm aware that Pentax, unlike Nikon, is not using colour to assist track a target. This is a pity.

Dan

PS. Ron, are you colour blind? (Not trying to be nasty.) The top is orange.
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