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veejaycee

Electronic shutter distortion

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veejaycee

We all know the effects of the Electronic shutter on moving subjects or when used from a moving platform but from the results of a discussion on another forum I recently reversed my previous habit of using mainly M shutter and swapping to E as necessary to one of using E shutter as standard and switching to M when subject movement was a factor. However, I was doing some tests yesterday to check the bokeh on my Canon FD 300mm lens which, when fitted with its matched X1.4 TC shows just a little nervousness and CA with the very twiggy background to my bird feeders. Without the TC the lens is fine but I noticed this severe distortion from using the E shutter on some of the files. I don’t stand nor hold a camera quite as steadily as I used to so I was using a monopod and light levels were low (see Exif). I was shooting CL to allow for misfocus knowing that I was not holding quite steady. This method has improved my hit rate allowing for some subject movement when shooting with a long MF lens - some even shoot BIFs this way with MF lenses. The distortion you see in two images is the result of very slight camera movement and E shutter. The day was still – in fact foggy and there was no swaying of the bird feeders. Shooting CL allowed me to get some sharp images as you can see and with no distortion usually the second or third of a 5 shot burst - while the distortion is in the first of each sequence as I press the shutter. I’m really surprised at the amount of distortion when camera movement was minor. I'm aware that the E shutter of the XT1 takes as much as 1/15th sec to pass fully across the frame while exposing/activating each row of pixels at the set shutter speed or auto shutter speed but I didn't expect this sort of distortion even taking into account the relatively slow shutter speed 1/300 for the focal length and and minor camera movement. I shall rethink my use of the E shutter with long lenses.

XT1, Auto E shutter, Canon FD 300mm f4L @ f4, ISO 5000 and shutter speed as shown.

First of each pair is distorted.

XT1S0126s.jpg

XT1S0128s.jpg

XT1S0133s.jpg

XT1S0134s.jpg

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Christopher

Wow, how interesting. The distortion must be particularly exaggerated because of the long focal length like you say. Presumably a long lens with image stabilization could overcome this to some extent? I've only tried one long adapted lens before, a 120mm macro, I quickly gave up because I couldn't really shoot anything hand held, 300mm must feel so shaky!

I've largely avoided using my electronic shutter for fear of distortion, I worry about subtle distortion that I won't perceive until later.

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veejaycee
1 hour ago, Christopher said:

I've largely avoided using my electronic shutter for fear of distortion, I worry about subtle distortion that I won't perceive until later.

That's what worries me. It is used by some to avoid shutter wear and some use ES for street - a stealth thing - but if I can get this sort of distortion through the extra camera movement involved in initial shutter press, then it seems likely there will be some distortion - if not in walking figures at about 3 MPH - then at least in their forward swinging arms and legs moving at 6 MPH.

I've seen plenty of examples of the phenomenon in aircraft props, cars and even running children with wide to portrait lenses but obviously one needs to be more careful with long lenses that will magnify camera movement especially when you consider sharpness of the second and fourth shots above which at 1/300 sec is actually pretty good for a monopod mounted 450mm equiv lens.

Here are 3 taken a few days ago - full size crops from XT1, 300mm + X1.4 TC (equiv 630mm) 1/680 @ f4, ISO 1600 (gulls) and 1/850 @ f5 ISO 3200 (fluffy thing) again with a monopod.

XT1S0027.jpg

XT1S0029.jpg

XT1S0118.jpg

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Christopher

The sharpness really is quite impressive considering the focal length and adaptors!

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artuk

I don't think your shutter speed of 1/300s has any impact on this problem - I think it would occur at any shutter speed as the issue seems to be the sensor read out speed which when using electronic rear curtain is the speed at which the rows of pixels are cleared down. As you rightly identify it looks at if slight camera movement combined with a long lens has resulted in something similar to subject movement, which resultant distortion /,smearing of the image. I have a camera with an optional fully electronic shutter and generally avoid it as it decreases the bit depth to achieve it, therefore limited the ability to push and pull shadows and highlights. The Sony sensors as used by Funk have a number of "watchouts" in various modes -,for example bit depth can be reduced in continuous shooting modes, I assume to lower the demands of moving.large volumes of data around very quickly - and its always worth being aware of these issues to avoid unexpected "gotchas". Until I saw your post I wouldn't have thought of camera movement with electronic rear curtain causing such problems, but logically there is no reason it wouldn't just like subject movement, as your samples show. For the reasons mentioned above I too shoot with mechanical rear curtain unless a situation warrants electronic. Can electronic rear curtain be used with flash modes? Just pondering how that might turn out too, given all the sync issues when using flash.

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veejaycee
11 hours ago, artuk said:

I don't think your shutter speed of 1/300s has any impact on this problem - I think it would occur at any shutter speed as the issue seems to be the sensor read out speed which when using electronic rear curtain is the speed at which the rows of pixels are cleared down. As you rightly identify it looks at if slight camera movement combined with a long lens has resulted in something similar to subject movement, which resultant distortion /,smearing of the image. I have a camera with an optional fully electronic shutter and generally avoid it as it decreases the bit depth to achieve it, therefore limited the ability to push and pull shadows and highlights. The Sony sensors as used by Funk have a number of "watchouts" in various modes -,for example bit depth can be reduced in continuous shooting modes, I assume to lower the demands of moving.large volumes of data around very quickly - and its always worth being aware of these issues to avoid unexpected "gotchas". Until I saw your post I wouldn't have thought of camera movement with electronic rear curtain causing such problems, but logically there is no reason it wouldn't just like subject movement, as your samples show. For the reasons mentioned above I too shoot with mechanical rear curtain unless a situation warrants electronic. Can electronic rear curtain be used with flash modes? Just pondering how that might turn out too, given all the sync issues when using flash.

Yes, it hurt my aging brain a little but I think I have it sorted now. Using a reciprocal shutter speed is advised to reduce camera shake but it doesn't have any affect on subject movement - that is to say - my using a 600mm lens might magnify camera movement by approx X13 (over the human eye) but the subject is moving no faster. Thus the gulls with no camera movement at reciprocal E shutter speed weren't moving fast enough to distort. For the feeder shots I was stood awkwardly on steps with the monopod on the step below which caused me to push the shutter less carefully than usual so the feeders, although stationery and at a little less than the reciprocal E shutter were distorted by camera shake magnified approx X7 times. Reciprocal shutter speeds with the E shutter can be fast enough to stop some subject movement depending on the speed of that movement but it appears the E shutter cannot be trusted to prevent camera shake especially at long focal lengths. Anyway, I shall revert to my previous method of M shutter as standard and E shutter for certain purposes.

A global E shutter would solve the problem. I've read elsewhere that using the E shutter affects bit depth but I don't understand why that is or whether a global shutter would have the same problem.

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artuk

I really don't think your shutter speed has any bearing on the result. You could have shot at 1/4000s and got the same result. The movement may not have occurred during the exposure, but during the relatively slow readout speed of the sensor when it is completing the exposure without a shutter. If as you say it takes 1/15s to clear the sensor, that is fixed regardless food your actual shutter speed. Therefore effectively the sensor read out speed always equals an effective "shutter speed" (though not an exposure) of 1/15s (if that value is indeed correct) - therefore the chance of camera shake during that time as the sensor is cleared down is potentially significant if the sensor is still on and able to capture light hitting it. So effectively - don't use electronic rear curtain with long lenses, there is a significant chance of camera shake regardless of actually shutter speed. In this case mechanical rear curtain is much safer - and I would probably be tempted to turn off electronic first curtain too - although that blunts shutter response on my cameras.

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veejaycee

I shall stear clear of E shutter anyway and, as you say definitely not for long lens use.

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artuk
1 hour ago, veejaycee said:

I shall stear clear of E shutter anyway and, as you say definitely not for long lens use.

the camera I have that feature on isn't one Id use with Tele lens, and I leave silent shutter off for other reasons - but there is a lesson to be learnt there.

global electronic shutter is coming in the next couple of generations - though it may com with other compromises. I'm convinced most cameras won't have mechanical shutters in a few years. Lets hope they fix all these weird issues!

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