Weird behavoir with EM1 and 10 stop ND

Sootchucker

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hi guys, tried my lee big stopper over the weekend and got some weird issues on my EM1. I had the camera on a Tripod, no IS, release by remote shutter cord etc. I focused with the ND on (it still focused and I got the Green AF confirmation), but after the long exposure NR finished, I reviewed the image and at 5x magnification it was very apparent that the image was very blurry. I put this down to false AF confirmation with the big stopper on, so removed it, focussed again, and then slid the lens (the 12-40 F2.8) back into manual making sure I didn't touch the focus ring. I then took a test photo with the ND off, and as suspected, it was razor sharp. then very carefully attached the ND into the holder (again without moving the lens) and look some more test shots, and again they were all blurry ?

thinking it might be a faulty filter, I swapped the body for my Panasonic GX7, using the same Olympus lens and shot some more test shots and they were all razor sharp with / without the filter ?

Any ideas what might be the problem with the EM1, or do they just not like very long exposures ?
 

Growltiger

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What sort of blurry? If it can't be focus, and it is on a good tripod, then what about ISO?
How are you setting exposure?
Are you allowing it to use a very high ISO that degrades sharpness?
 

Sootchucker

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  • Thread Starter Thread Starter
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Thanks for the reply. ISO and exposure isn't the problem as ISO is set manually to ISO200 (on both cameras), the tripod is a carbon fibre unit with a heavy duty ball head, that usually takes my D800 and lenses so I don't think it's that.

It's not double line blurry (as you would get from shutter shock or camera shake), just a general blurriness to the image, which is even noticeable on my Retina Macbook Pro without zooming in. The GX7 by comparison produces tack sharp images every time even using the focal shutter (not the electronic one) ? Weird ?

I've been able to reproduce it every time on the EM1, not one image out of about 20 came out sharp, however sliding the ND out of it's holder without touching anything else (lens still in manual focus mode), produces tack sharp images on the EM1 ?
 

Growltiger

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The presence of the filter could change the focus - at least in theory. Try a test. Aim at a very bright object such as a lightbulb, with the filter in place. Zoom in to see if the focus is sharp. Is it sharp in the viewfinder? Now try a photo. Is it sharp?
 

AlanGinman

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With a 10 stop filter on an f2.8 lens you are asking the camera to focus at an effective aperture of f66 or thereabouts. That's a big ask and might just be too much for the autofocus system. Maybe you just need to focus without the flter and put it in afterwards, as you have already tried.

Just a thought.

Alan
 

SysteX

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Aren't the AF and MF ring positions independent? If you use AF with the clutch forward, then slide the clutch back, focus will snap to wherever the MF ring puts it, not necessarily where the AF had put it. As an aside, this is an easy way to pull focus when shooting video... Focus with AF on your first subject, then focus with MF on your second. Sliding the clutch back and forth will pull focus between the two subjects.

The way I handle this is to use MF mode on the camera with the clutch still forward. I have the AEL button setup to to trigger AFL in MF mode. Without a filter on, I'll pick my focus point, use the AEL button to get focus, then put the filter on. No need to slide the clutch at all.
 

fortwodriver

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Sounds like your filter adaptor isn't plane-parallel. What if you hold it up against the lens, using the hood to keep it parallel, do you still get a blurry image?

By the way, I've tested using the clutch on the 17mm lens like that SysteX. According to my find, if you focus manually, then snap to AF and refocus, then snap back to manual, the manual position will be at some random focus position - not the one you originally selected. Usually that random position doesn't cause things to become completely out of focus, but it will be enough to ruin whatever was set via AF.
 

pdk42

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I realise this isn't the cause of your problem, but try using AF mode 3 (back button focus) rather than using the manual focus clutch. That way you are guaranteed to get the same focus on successive shots.
 

letsgofishing

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I use a 9 stop ND filter on my 1240 for my seascape photography all the time and don't have this problem. The AF system manages to find focus with it on. On the rare occasions it has hunted, I shine a torch on something around 8-10ft away and focus on that.
 

Klorenzo

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Are you using a single small box AF? Otherwise it could be focusing on a different place when the filter is on.
 
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