200mm zoom @ f/2.8 - can't nail focus

Forums › Digital Imaging › 200mm zoom @ f/2.8 - can't nail focus - shutter speed?

Batman

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#173476 25-May-2015 09:35

Hi I bought a Tamron 70-200mm 2.8 VC over the weekend and I feel a bit stupid lol ... so please bear with me.

When chasing a toddler going at mild-medium speed towards the camera from around 7-10m away I am getting motion blur even at 1/2000s. I am thinking my shutter speed isn't fast enough, or is it something else to learn.

Body: 5D Mark III
Lens: AF instantaneous no measurable lag compared to Canon's Mk II, but you know that the Canon always focuses "Faster", and you can perceive it. What I'm saying is this lens focuses as fast as all my other Canon and third party lenses if not faster.
AF mode: single shot (as opposed to AI Servo). refocus every shot, no bursts. bursts would not help as the kid has moved nearer by the next burst without refocussing.

Object moving sideways more chance of getting sharp frozen pics at 1/350-1/500. Fixed objects it nails it a 1/8s !!! the VC is that good.

SO. what am I doing wrong?
- faster shutter speed - it's not even doing it at 1/2000!? (won't help if the subject has left the focus field between pressing the shutter although I swear if there was any lag it would be measured in micro to miliseconds. the lens is that fast.
- use AI Servo (easy to say but couldn't tell at the time, now the weather is gone crap and kids are not going to run around in the park for me to do this 'test')
- turn off VC?
- other tips

Does AI Servo predict the object would have moved and so focusses nearer? if not then why would it have an advantage on such a seemingly lagless AF lens?

I understand the lens MAY be a problem, but I have no experience at objects coming towards you at 200mm at such a shallow DOF. I thought the lens would cope.

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#1311086 25-May-2015 09:56

1/2000th should be more than sufficient. Sounds like a focus issue, possibly how you're using it. Post a photo, difficult to diagnose without. Send privately somehow if you don't want it public.

Does it focus ok on static subjects?

I only buy OEM lenses, I've had too many problems with third party. I also abandoned Canon because of focus issues, but the 5D3 is meant to be an improvement.

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#1311089 25-May-2015 09:57

Hi - yep, I think you're on to it with the focus mode settings. I would suggest you should definitely be set to AI Servo mode for any photography where the subject is moving as it will 'follow focus' with the subject, whereas One Shot mode will set the focus point at half push and by the time you've fully pressed the shutter your subject will have moved... so I would suggest that you're seeing a general lack of focus, rather than subject movement causing the blurring.
The AI Focus mode is supposedly the best of both worlds as it should detect whether your subject is moving or not, but I tend to stick to either the Servo or One Shot. Good luck with those fast moving, unpredictable subjects of yours...

Cheers,
Mike

Photographer/Videographer clickmedia.nz

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#1311092 25-May-2015 10:04

timmmay: 1/2000th should be more than sufficient. Sounds like a focus issue, possibly how you're using it. Post a photo, difficult to diagnose without. Send privately somehow if you don't want it public.

Does it focus ok on static subjects?

I only buy OEM lenses, I've had too many problems with third party. I also abandoned Canon because of focus issues, but the 5D3 is meant to be an improvement.

Hi Timmay. Yes I understand. I have never had focus issues with any lens I put on a 5D3. Some need MFA, which is easy to do. I think your problem was a 7D issue. THe internet is full of them, sone legit, though mostly not.

My question arose because I've never had to shoot at such shallow DOF at such a close distance at such a rapidly-changing-within-DOF object. Problem with close distance is the shallowness of DOF is much amplified.

The lens has no trouble locking on static subjects. And man, I thought the 24-105L / 85 1.8 was fast. This is even faster. But still not good enough ... I hope AI Servo has a better chance.

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#1311093 25-May-2015 10:04

clicknz: Hi - yep, I think you're on to it with the focus mode settings. I would suggest you should definitely be set to AI Servo mode for any photography where the subject is moving as it will 'follow focus' with the subject, whereas One Shot mode will set the focus point at half push and by the time you've fully pressed the shutter your subject will have moved... so I would suggest that you're seeing a general lack of focus, rather than subject movement causing the blurring.
The AI Focus mode is supposedly the best of both worlds as it should detect whether your subject is moving or not, but I tend to stick to either the Servo or One Shot. Good luck with those fast moving, unpredictable subjects of yours...

thanks. I'll never know today. it felt instantaneous. press button -> instant lock -> instant snap. but the horse had bolted in less than an instance!

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#1311096 25-May-2015 10:06

I have a feeling even the AI servo won't keep up at such a close distance. it's because the DOF is so shallow at close range. sports is different because the subject is miles away that you are targetting. compared to the kid. who knows ..

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#1311102 25-May-2015 10:24

It would be a heroic feat to achieve accurate AF at 200mm f2.8 and close focus distance on a moving target. The depth of field is razor thin. You'd probably also need to use MFT (AF fine tune) even to get critical focus for static subjects, and even then, the DOF is so thin that you might get eyelashes in focus, but blurred eyes. IMO you're expecting miracles if you're shooting at f2.8.
So:
Use a smaller aperture - perhaps F8 or smaller. Shoot in more light, or increase ISO. I don't think you should need 1/2000 sec shutter - as if the subject is so close and moving so fast that you'd need that speed to stop motion, you've got next to no chance of the AF system being able to keep up.
Learn to use the AF-ON button with continuous servo, set the shutter button to release only, actuate AF (and IS) holding the AF-ON button, track the subject, and gently squeeze the shutter button to shoot, but keeping focus-tracking on constantly with the AF-ON button.
If you're using IS (= VC in tamron speak), then never use it with a quick depress of the shutter button in either single-servo or continuous servo mode. You need to allow the stabilisation time to settle and lock - or it will add blur - not reduce it. - so either half-depress the shutter for a second or so before release - or better - use the AF-ON button as above to keep tracking your subject.
Practice. There are many settings to choose from. What the perfect combination of settings may be for someone else may not be the best for you - and vice-versa.

timmmay

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#1311104 25-May-2015 10:26

Useful chart on this page.

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#1311110 25-May-2015 10:40

Thanks Fred. Good to know it is not easy! Wow a new dimension. I thought tracking birds was difficult.

timmmay

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#1311112 25-May-2015 10:41

Why, what's wrong with the Tamron?

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#1311114 25-May-2015 10:42

I ... Just ... Can't ... Carry it!

timmmay

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#1311134 25-May-2015 10:49

That type of lens is pretty heavy, I tend to have to hold it up to my eye for up to an hour at a time, no tripod or anything. When I got the 70-200 I changed my gym routine so I could carry it for that amount of time - seems to use chest, bicep, forearm, and shoulder muscles.

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#1311137 25-May-2015 10:56

I can easily use it on a 1kg body on its own. Eg indoor sports/indoor anything from a distance (which i don't do). But I can't see how it's going to go in a bag along with other stuff.

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#1311142 25-May-2015 11:09

joker97: Thanks Fred. Good to know it is not easy! Wow a new dimension. I thought tracking birds was difficult.

It is difficult - and a topic fraught with difficulty:
Most reviewers aren't experienced pros - but techno-geeks, so many reviews aren't very useful when it comes to opinions about AF performance.
More useful reviews by experienced pros usually suffer bias - not deliberate, but if you'd spent years perfecting technique using certain dslrs, then unless you'd perfected technique with a model under test, it would be tempting to conclude that any apparent deficiency may relate to the camera - not the person behind it.
Above basic consumer cameras, the AF systems tend to have complex settings/options. They might also have "magic" dynamic modes which might work, but wouldn't be the best mode to use for any particular purpose, except perhaps when handing the camera to somebody else to take a snapshot.

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#1311143 25-May-2015 11:14

i know i have major problem tracking birds close up. (ie - never once got a shot i'm happy with. but that's with a consumer zoom to 300mm on a consumer crop sensor).

i guess the kid running towards you is similar. thanks. will do some practice.

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#1311183 25-May-2015 11:29

joker97: I can easily use it on a 1kg body on its own. Eg indoor sports/indoor anything from a distance (which i don't do). But I can't see how it's going to go in a bag along with other stuff.

With a bigger bag, on its end - like this. That's not my bag, but I have a think tank security (I think), which fits two full frame bodies, 70-200, three other decent size lenses, extension tubes, radio triggers, four flashes, four battery packs, filters, batteries, cards, a drink bottle (sometimes), flash accessories, etc.

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