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Intermittent faded strip along left edge of frame (A7s)


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Hi there,

 

So today when I was reviewing some pictures that I took with my A7s I noticed a strange faded strip that runs vertically along the lower left hand side of the frame. It's as if the brightness of this small patch has been brought down.  It's not small as it's about 150 pixels wide and goes about half way up the frame.  This is the second time that I have noticed this issue. I had the same problem with a number of pictures that I took last week.  Both times it's been very specific frames on a tripod that haven't moved much, but the issue is identical.  The first time it was a warm day of about 25 degrees C, today it was -5.

 

What is especially strange is that it will appear and disappear between pictures taken on a tripod in the same spot.  I can see no reason why it's there or why it disappears. The only constant is that both times it's happened it's been after I've been doing long exposures for a bit.  I've tried briefly to recreate it but have had no luck.

 

I've been shooting on Canon FD lenses adapted to fit my A7s.  The first time I was shooting with my 50mm but today was with my 24mm.  I can't see anything wrong with the lenses or the adapter.  It also seems a bit too straight for it to be something with the lens.

 

I've attached a couple of crops which show the left side of the frame.  These images are the full vertical resolution of the image so you can see how the strips fade away.

 

1st image - https://drive.google.com/file/d/0B_UH1Uv2rYdMOUlOX2VqTEppV1E/view

 

2nd image - https://drive.google.com/file/d/0B_UH1Uv2rYdMVmdtZzFoZHJoQzQ/view

 

 

If anyone has got any ideas it would be great to hear from you.  Obviously I'm really hoping that this is an easy fix/ solvable glitch, I'd hate to find that this is anything more sinister.

 

 

Thanks in advance for your help, I really appreciate it.

 

Jamie

 

 

 

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It may be a shutter problem even tho it's a vertical 

travel shutter. If it's worse at faster speeds and it's 

less obvious or never occurs at "tripod speeds", it 

is definitely shutter. I suspect a drifting blade that 

changes the slit width mid-travel. At a really slow

[tripod] speed, there is no traveling slit. One blade 

set clears away, the exposure duration times out, 

the the second [closing] set covers the sensor.  

   

You mention using a tripod, but that doesn't tell me 

your actual shutter speeds. If the speeds were well 

below synch speed, then forget what I wrote above. 

You said it happens AFTER doing long exposures, 

so that suggests the faulty images are NOT from a 

long exposure. 

   

    

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Thanks for your thoughts.  Unfortunately all the instances where it has happened have been at exposures between 1/8th and 30 second, so the above probably doesn't apply.

 

In a string of about 35 pictures I took of the same scene, the bar appeared identically in about 28 of them. The position of the line is identical every time, the only thing that changes is the opacity.  Within this batch of pictures the only time it disappeared was when the shutter speed increased.

 

 

What is interesting is that in a set of long exposures I was doing, the line appeared for several pictures all over 20 second exposure, then after slightly shifting the tripod and moving to a 1/30 sec exposure the line disappeared. For the rest of the day I didn't do any long exposures and had no issues.

 

In another instance where I had been taking long exposures I finished with a 2.5 second shutter and the line appeared. I then turned my camera off and moved to another location and about 25 minutes later took another 2.5 second exposure, the line didn't appear.

 

 

 

It seems in some way to be linked to long exposures but there are inconsistencies, times (within the same scene batch) when it shows at a fast speed (i.e. 1/8th)  but not at a slower speed (i.e 1 sec). 

Could it be the sensor? Is it some kind of reflection/ shadow caused by the FD lens adapter when the scene is lit a certain way (that's probably a stupid thought)?

 

It's hard to explain but I hope I've done a reasonable job, if not please let me know and I'll try and make it clearer.

 

 

Again if anyone has and thoughts I'd be very grateful. Thanks in advance for the help!

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I'll give it a go.  As things stand I've not actually been able to recreate the issue even when shooting with my FD lenses so it would be difficult know if switching lenses would sort the issue or if it just isn't happening.

 

The good thing is that it's not a constant issue with a massive impact, but it is always worrying when expensive kit acts strangely.

 

Thanks for your thoughts!

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