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-   -   HELP! badly underexposed at 1/8000 (https://e-group.uk.net/forum/showthread.php?t=45688)

piglicker 25th July 2017 12:26 PM

badly underexposed at 1/8000
 
hi guys,

has anyone else noticed that photos shot at 1/8000 are badly underexposed?

i came across it will auto-bracketing on a sunny day .. all the exposures shift by what looks like the correct amount, but the 1/8000 shots are nearly black. i was using the 12-60mm SWD at the time...

advTHANKSance

Ross the fiddler 25th July 2017 12:41 PM

Re: badly underexposed at 1/8000
 
Quote:

Originally Posted by piglicker (Post 422400)
hi guys,

has anyone else noticed that photos shot at 1/8000 are badly underexposed?

i came across it will auto-bracketing on a sunny day .. all the exposures shift by what looks like the correct amount, but the 1/8000 shots are nearly black. i was using the 12-60mm SWD at the time...

advTHANKSance

Is it the camera's setting, or is it the failure of the lens aperture blades? Both my SWD lenses (50-200 & 12-60 lenses bought used over the last couple of years) have failed like that. On the E-5 there is the Preview function button on the front & that will close the aperture blades down to whatever aperture set on the camera (e.g. in Aperture Priority or Manual) & if selecting f22 & exercising it then the fault may show up (like mind did & stuck closed). The other possibility could be the shutter mechanism, but I suspect the lens in this case, but can still be repaired, which is what I intend to do with my 12-60 SWD lens.

piglicker 25th July 2017 01:03 PM

Re: badly underexposed at 1/8000
 
i don't think it's the lens - but it's worth doing some tests, so thanks for the pointer...

i think i've experienced the problem on other lenses, and i was wide open on aperture-priority while rattling off these brackets (which is why the camera cranked it up to 8000).

once the sun makes another appearance, i'll play around. might be a while, though - i'm in scotland :)

Petrochemist 25th July 2017 01:07 PM

Re: badly underexposed at 1/8000
 
It sounds to me as if your lens aperture won't go wide enough.
1/8000 is a fast shutter speed, so needs unusual conditions.

I believe the maximum aperture of this lens is f/2.8 to f/4 'Sunny 16 rule' suggests with the aperture wide open your ISO would need to be at least 250 (500 if zoomed in) for roughly correct exposure, when in full sunshine. A little bit of shade will make it considerably worse.

piglicker 25th July 2017 01:11 PM

Re: badly underexposed at 1/8000
 
just tried it with the lens off, and the ISO bumped up...

1/4000 is fine
1/5000 is maybe slightly dark
1/6400 is maybe 2/3 stop dark
1/8000 is virtually black

maybe my shutter is going too fast, or the metering system can't do its' sums beyond 5000...

Tordan58 1st August 2017 09:40 PM

Re: badly underexposed at 1/8000
 
Could it be a sticky shutter?

piglicker 2nd August 2017 11:30 AM

Re: badly underexposed at 1/8000
 
ah, so the first curtain is a bit lethargic and the second curtain is on cue?

could be .. and i guess if the sticky-lag is only very small, then it'll only show up at fast shutter speeds.

i'll maybe look into fixing it, but i get the feeling it'd cost a fair bit and it's a very edge-case scenario. maybe i'll change my mind on that after a few more ruined 1/8000s shots :)

Ross the fiddler 2nd August 2017 11:41 AM

Re: badly underexposed at 1/8000
 
If the metering is showing the shutter speeds (at 1/8000 sec) are fine & it comes out dark, then it is either a slow acting lens aperture mechanism or camera's shutter curtain. Using the Preview button on the camera's front (E-M1's) with aperture closed down (up to f22) will show if it is failing or not & if that is OK then the shutter may very well be the problem. Just make sure the lens contacts are clean though.

Quote:

Originally Posted by piglicker (Post 422410)
just tried it with the lens off, and the ISO bumped up...

1/4000 is fine
1/5000 is maybe slightly dark
1/6400 is maybe 2/3 stop dark
1/8000 is virtually black

maybe my shutter is going too fast, or the metering system can't do its' sums beyond 5000...

That doesn't say anything really, because it still depends on how much light there is & proper metering is needed to show if that fast shutter speed is just too fast for an exposure, depending on other settings, but the metering will show that.


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