Motion blur, hypersync, shutterspeed etc.

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Andrew H

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Recently I have been having issues with blur in the studio with studio strobes and I cannot work out why so was hoping someone may be able to offer some advice.

A brief as possible explanation of my situation:

Kit: 5D3 mostly with 85mm f1.2, Bowens Gemini 400W heads, Yungnuo RF-602
Subject: Models

Problem: I can sync at 160th, just - 1 out of 20 shots will have banding so I often slow down to 125th. Now whilst I think I understand the technical side of flash duration freezing motion, I am still getting soft shots with the Bowens heads and I cannot work out why. The only reason I can think of is 'shaky hand syndrome' - I drink coffee and smoke and usually don't have the steadiest of hands. With the gripped 5D3 and 85mm combination being quite heavy I do find myself moving slightly when focusing. I have tried using a tripod to eliminate the problem, and it does, but on 99% of shoots I am moving around too much to keep the tripod in one place.

So...probably a question I should already know the answer to, but - is the softness caused by the shutter speed and shaky hands? I am usually at f11 or higher so the focal plane wouldn't be an issue at the distance I am shooting at.

If the issue is the shutter speed would PW Mini TT1 and Flex TT5 allow me to alter the x-sync enough to eradicate the problem? Does the YN-622c offer the same capabilities?

Sorry for the long post! Any help will be greatly appreciated :)
 
I also smoke and drink far too much coffee, and I'm old and dropping to bits too, but I don't have this problem:)

The Bowens don't have the shortest flash duration in the world, this is a possible cause if there is a lot of subject movement. Even so, there shouldn't really be a shake problem unless you smoke even more than I do or have some other problem causing your hands to shake.

You say that you can't use a tripod for most of these shots - how about a monopod, or a length of chain fixed to the tripod bush that you can stand on and hold taught?

Are you sure that the problem is all down to camera shake anyway? If you use very small apertures then you should expect some unsharpness caused by diffraction limitation.
 
Garry Edwards said:
I also smoke and drink far too much coffee, and I'm old and dropping to bits too, but I don't have this problem:)

The Bowens don't have the shortest flash duration in the world, this is a possible cause if there is a lot of subject movement. Even so, there shouldn't really be a shake problem unless you smoke even more than I do or have some other problem causing your hands to shake.

You say that you can't use a tripod for most of these shots - how about a monopod, or a length of chain fixed to the tripod bush that you can stand on and hold taught?

Are you sure that the problem is all down to camera shake anyway? If you use very small apertures then you should expect some unsharpness caused by diffraction limitation.
Click to expand...

Hi Garry,

Thank you for your reply.

My shakiness does also seem to increase depending on the importance of the shoot so anxiety may not be helping (also results in more smoking and more coffee due to lack of sleep). Although - as you say it shouldn't be a problem with little to no subject movement. I had my thyroid levels tested years ago but perhaps it's time for another checkup!

I think a Monopod could definitely be a possibility so will give this a go on the next shoot.

I'll be honest - I hadn't considered diffraction limitation but it is certainly a possible cause.

I'm not sure if this will be of any help in diagnosing the problem further, but this is a 100% crop of a recent image (only post was colour correction and +0.4 exposure correction). Shot at 1/125th at f16 ISO 100 with 85mm:

screenshot20130401at120.png


(Imageshack seems to have changed my colour correction anyway, so please ignore that part!).
 
You need to do some tests. Possible causes of softness:

Diffraction. You will definitely get some noticeable softening at f/16 - don't go higher than f/8 for max sharpness. This is my guess, and your sample crop looks like diffraction softening to me.

Subject movement. The effective flash duration from studio heads is much longer than the quoted t.5 times, like 2x to 3x longer to match equivalent shutter speeds, and flash durations get longer as power is reduced with studio-type flash heads. But unlikely in this case if the subject is not moving.

Misfocusing. Again unlikely at f/16, but be aware that the 85/1.2 is known for focus shift and this will be noticeable at say f/2.8 or f/4.

Camera-shake. Unlikely I think, and usually has a characteristic look to it, but possible. If this is a problem for you, get an image stabilised lens.

Your sync speed thing is common with radio triggers, and with the RF-602 you'll not get the full 1/200sec. Shooting at max x-sync speed is not recommended for studio flash due to the longer flash duration (see 5D3 handbook on this) and since shutter speed usually makes no difference in studio situations, 1/125sec is not a bad default. Batteries may be low in the triggers.
 
Hi Richard,

Thank you, that is all very helpful. I will open up to f8 using a monopod on the next shoot and check the results. I also have a 24-105 IS so will give this a go too.

I wasn't aware of the 85mm focus shift issue, I'll have a read up on it now.

I agree, camera shake does have a characteristic look to it which is what initially baffled me when looking at the softness. The triggers could definitely do with some new batteries, I hadn't realised this would affect the sync so I'll get these changed before the next shoot!

Thank you both again, very helpful advice and very much appreciated. :)
 
Thanks Steve, that's a great article and experiment. Very interesting to see how much the laser point still moved with the remote shutter using a tripod, and more so how much it moved handheld! Certainly makes me feel a bit better about my shaky hands!
 
Andrew H said:
Hi Richard,

Thank you, that is all very helpful. I will open up to f8 using a monopod on the next shoot and check the results. I also have a 24-105 IS so will give this a go too.

I wasn't aware of the 85mm focus shift issue, I'll have a read up on it now.

I agree, camera shake does have a characteristic look to it which is what initially baffled me when looking at the softness. The triggers could definitely do with some new batteries, I hadn't realised this would affect the sync so I'll get these changed before the next shoot!

Thank you both again, very helpful advice and very much appreciated. :)
Click to expand...

Do one test at a time to identify the problem by process of elimination. My hunch is diffraction, so try that first without the monopod.

Camera shake is always present of course when hand-holding. Some folks seem to think that it magically disappears when you get above the focal length/shutter speed rule, but it's only reduced to acceptable levels. Check out Nikon's recommendations for getting max sharpness out of the D800's 36mp - only use the best lenses, no higher than f/8, tripod with mirror lock-up.

I used a laser to check camera vibration many years ago, as in that link, but the test is flawed because a lot of the most visible vibration occurs when the mirror slams down, after the exposure. The most critical shutter speeds are always between 1/30sec and 1/4sec, especially 1/15sec to 1/8sec. But you don't need a laser - just get a longish lens, and use live view on max magnification to see how hard it is to hold the camera steady. Then switch on image stabilisation and witness a massive improvement!

Edit: Canon 5D Mk3 has an unusual mirror mech, in that it is positively driven both up and down instead of just flapping against a sponge buffer - that's what makes the quiet mode so effective, and also helps the similar 1DX to its very fast frame rate. I've not tested this, but I suspect it may mean there is less mirror vibration too.
 
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Sorry to revive an old thread, but I am looking for advice again as this still seems to be an issue on shoots.

This was shot at f8 on 5D Mkiii with 85mm L lens (100% crop) No sharpening applied:

bg5q.png


The softness does look similar to the image I previously posted. However, I've come to realise this may be my lack of focussing skills rather than diffraction or similar. Here is a 100% crop of the midriff which is sharper but still soft:

w4vq.png


Only adjustment was colour balance for this image. Sorry for not posting the full image, unfortunately I can't due to publishing reasons, but I will be happy to post crops from other shots to show comparisons if it will help.

So... is this an issue of diffraction, my focussing skills, lens/body issues or something else? Again, any help or advice will be greatly appreciated.

I am tempted to take the camera body and all lenses in to be adjusted by a professional just in case. I seem to remember Calumet offered this service, is this still the case? Had a look on the site but could only find sensor cleaning services. If not does anyone have any recommendations for this service please?
 
Need to see a full image that you're unhappy with, and a cropped area from it, with all technical details.
 
Would you mind if I sent you a link to the uploaded file? That really is as much as I can post publicly unfortunately!
 
Andrew H said:
Would you mind if I sent you a link to the uploaded file? That really is as much as I can post publicly unfortunately!
Click to expand...

If you like, though it would be better to shoot something specific that you can show, as I originally suggested. Preferably a subject with some depth so that if there is a sharp plane, we can see where it is.

There is too much guessing from what you've posted above, but if guessing is the name of the game, the fact that you've said the problem goes away when you use a tripod suggests a simple miss-focusing issue, ie a technique thing.

If you're constantly moving around, and not checking and rechecking focus on a fairly constant basis, you will quickly drift outside the sharp depth-of-field zone.
 
Diffraction limitation is very unlikely to be the problem at f/8 on a full frame camera. There isn't an on/off switch, it's a progressive effect, but it's hard to spot at less than about f/16 on this camera.

Camera shake - yes, it's always present to some degree or other, and we have varying degrees of ability to hold a camera steady, but although I could be wrong, this doesn't look like camera shake to me, it looks out of focus.

If it is a focus problem, there are a range of possible causes, from you expecting your camera to be as clever as it says it is but choosing the wrong focus points (if you're allowing your camera to do this, which I hope you're not) to focussing on the wrong part of the subject entirely, or forgetting to re-focus if focussing manually, or it could be a fault with the camera.

There are basically a couple of things you can do, after eliminating the possibility of allowing the camera to choose the wrong focus point by switching that off in the menu. You can do a series of shots of a deep subject, for example a ruler or a fence, and see whether the bits that are actually sharp are the bits that should be sharp. Take these shots at say f/4, f/8 & f/16. Do it both hand held and on a tripod.

Or you can do as Richard says, and post the results on here. Then we can all argue with each other and confuse you with different answers:)

But at least one of us, probably Richard, will come up with the right answer.
 
Thank you all again for the replies and advice.

Richard, you are right - I can see how it is difficult to see from one shot and a small crop. Thank you for the offer, I have now done some preliminary tests which I will show below rather than showing one image.

Garry, I agree, it does look like focus issues rather than camera shake, the catch lights seem to be a bit of a giveaway. I should have gone into more detail with my explanations - I use single point focus on AF and recompose. 90% of the time the centre point, but if absolutely necessary I will push to a point further out. As previously mentioned, I am using Bowens Gemini 400's with RF602's.

So here are my tests so far. These are on a tripod to start with and if needed I will take more handheld. I shot at f1.2, f4, f8 and f16. All have both centre point focus and just to check, the furthest right point (furthest top in portrait orientation). All shots were taken tethered.

f1.2 1/60s ISO100 Centre focus point (No flash)
gxew.jpg


f1.2 1/60s ISO100 Outer focus point (No flash)
rqx3.jpg


f4 1/125s ISO 100 Centre focus point (Flash)
q6h4.jpg


f4 1/125s ISO 100 Outer focus point (Flash)
8zx7.jpg


f8 1/125s ISO 100 Centre focus point (Flash)
pu4t.jpg


f8 1/125s ISO 100 Outer focus point (Flash)
om4j.jpg
 
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f16 1/125s ISO 100 Centre focus point (Flash)
fe9r.jpg


f16 1/125s ISO 100 Outer focus point (Flash)
fprr.jpg


Hope this will be of some help in diagnosing the problem! I can see immediately that it needs some micro adjustment for this lens. Also I think this probably is an issue with my focussing. I'm going to do some more extensive tests when I can.
 
Just some comments Andrew.

At f/8, it's not a diffraction issue. With flash, it's unlikely to be camera/subject movement blur, unless your subjects are in fact moving around. With standard Gemini heads (ie not the faster Pro versions) your effective flash duration is in probably in the region of 1/500sec equivalent shutter speed (depending on model number and power setting). Is there any subject movement? How/what?

That basically leaves miss-focusing, or an equipment error. Most likely the former, because you've said the camera is moving and the problem goes way when it's on a tripod. Also, your AF check above doesn't look too bad, though that's a poor test method. The distance must be realistic (not artificially close) and target should be square to the camera - it's neither there. Lots of threads on how to do this properly, try this one http://www.talkphotography.co.uk/forums/showthread.php?t=466800

There is a lot of talk about focus-shift issues with your 85/1.2 lens, but having used that lens (Mk2) quite a lot recently, and specifically looking for evidence, it's really not much of a problem and the critical apertures are f/2-2.8.

Focus-recompose using centre point can cause problems, but only when a) you're very close, b) point of focus is well off-centre, and c) you're at a very low f/number. None of those conditions apply here, though with the 85/1.2 you need to be aware.

Which leaves focusing technique, and the possibility that the camera distance is changing between focusing and shooting, and you don't have enough DoF to cover it. Check how much DoF you've got here http://www.dofmaster.com/dofjs.html Maybe servo-AF might be the way forward, though the caveat around possible movement blur needs to be clarified.
 
Hi Richard,

Thank you so much for the information and advice. :thumbs:

Movement is usually minimal - I tend to get models to move with each shot if they can so usually focus and recompose quickly once he/she has posed for the next frame (unless it's a bad pose!). I can see how this would cause issues and it may well be that I need to work on my focussing or slow the model down.

Thank you for the link - I have now used the DotTune method at the suggested distance from the chart and with the 85mm I ended up at +5. This method does seem far more accurate and consistant, and quick too!

I think it must be my technique - as you say all other possibilities are actually highly unlikely given the settings, equipment and subject distance, which does concern me. Not that I've been shooting for nearly as long as many on here, but it is something I will be practicing and bearing in mind a lot, lot more on future shoots!

Thank you again for the comments, really appreciate you and Garry taking the time to help out.

HoppyUK said:
Just some comments Andrew.

At f/8, it's not a diffraction issue. With flash, it's unlikely to be camera/subject movement blur, unless your subjects are in fact moving around. With standard Gemini heads (ie not the faster Pro versions) your effective flash duration is in probably in the region of 1/500sec equivalent shutter speed (depending on model number and power setting). Is there any subject movement? How/what?

That basically leaves miss-focusing, or an equipment error. Most likely the former, because you've said the camera is moving and the problem goes way when it's on a tripod. Also, your AF check above doesn't look too bad, though that's a poor test method. The distance must be realistic (not artificially close) and target should be square to the camera - it's neither there. Lots of threads on how to do this properly, try this one http://www.talkphotography.co.uk/forums/showthread.php?t=466800

There is a lot of talk about focus-shift issues with your 85/1.2 lens, but having used that lens (Mk2) quite a lot recently, and specifically looking for evidence, it's really not much of a problem and the critical apertures are f/2-2.8.

Focus-recompose using centre point can cause problems, but only when a) you're very close, b) point of focus is well off-centre, and c) you're at a very low f/number. None of those conditions apply here, though with the 85/1.2 you need to be aware.

Which leaves focusing technique, and the possibility that the camera distance is changing between focusing and shooting, and you don't have enough DoF to cover it. Check how much DoF you've got here http://www.dofmaster.com/dofjs.html Maybe servo-AF might be the way forward, though the caveat around possible movement blur needs to be clarified.
Click to expand...
 
You're welcome Andrew :) So assuming it's a technique issue, if it helps, this is how I would approach things when the camera is moving and/or subject.

Canon 5D3 has excellent AF. Suggest servo mode, single point, back-button AF activation. If the subject position in the frame is predictable, choose the appropriate AF point. If it's not, choose centre point, move back a bit, then crop to the final framing in post processing.
 
HoppyUK said:
You're welcome Andrew :) So assuming it's a technique issue, if it helps, this is how I would approach things when the camera is moving and/or subject.

Canon 5D3 has excellent AF. Suggest servo mode, single point, back-button AF activation. If the subject position in the frame is predictable, choose the appropriate AF point. If it's not, choose centre point, move back a bit, then crop to the final framing in post processing.
Click to expand...

Thank you, I'll definitely give the Servo Mode a go, I must admit I have only ever used single point AF as I was always told to set this when assisting and taking test shots, but it sounds as if it is something which could be very useful!
 
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