Moon with pixel shift resolution


pentaxian450

Link Posted 15/03/2017 - 01:47
RobL wrote:
So, to freeze movement in PSR I assume that whatever shutter speed would normally suffice then divide by four: say 1/500 sec would require a setting of 1/2000 sec. If the ISO is increased by four stops to suit I wonder if the noise will cancel any benefit? Further experimentation needed.

Your assumption is wrong. You need the same speed in PSR as in a single exposure shot. The problem encountered in PSR is that the four pictures aren't taken at the same time, but one after the other. If there is any movement in between the different exposure, then you get some blur, the extent of it depending upon how much movement occurred in between the different exposures. To make things worst, when movement is caused by wind, light objects, or objects with low mass and high "drag" will move more than heavy or low "drag" objects.
Yves (another one of those crazy Canucks)

RobL

Link Posted 15/03/2017 - 08:34
pentaxian450 wrote:
RobL wrote:
So, to freeze movement in PSR I assume that whatever shutter speed would normally suffice then divide by four: say 1/500 sec would require a setting of 1/2000 sec. If the ISO is increased by four stops to suit I wonder if the noise will cancel any benefit? Further experimentation needed.

Your assumption is wrong. You need the same speed in PSR as in a single exposure shot. The problem encountered in PSR is that the four pictures aren't taken at the same time, but one after the other. If there is any movement in between the different exposure, then you get some blur, the extent of it depending upon how much movement occurred in between the different exposures. To make things worst, when movement is caused by wind, light objects, or objects with low mass and high "drag" will move more than heavy or low "drag" objects.

I think you misunderstand me, I agree the exposure for PSR is the same as for a single shot but say you pick a speed of 1/500 then the timeframe for a PSR will be 1/125 sec (4x 1/500). In order to get a timeframe of 1/500 sec in PSR (4x 1/2000) you would need to adjust the ISO by four stops. This of course assumes that the interval between PSR exposures is instantaneous which may not be the case.

richandfleur

Link Posted 15/03/2017 - 09:58
RobL wrote:
I think you misunderstand me

I get you

RobL

Link Posted 16/03/2017 - 07:18
Abe_Normal wrote:
It would be interesting to output the four frames of the PSR image as separate files and see how many pixels the moon moves between them

I don't think there is that option.

tyronet2000

Link Posted 17/03/2017 - 11:35
I was sort of lead to believe the PRS was good for still life and landscape, static objects. and the files were processed in-camera to give one, in my case, RAW image. Have only used this mode a couple of times and thought it showed promise and hopefully will get the oportunity to try again.
Regards
Stan

PPG

MilesGreen

Link Posted 31/03/2017 - 07:14
RobL wrote:
Abe_Normal wrote:
It would be interesting to output the four frames of the PSR image as separate files and see how many pixels the moon moves between them

I don't think there is that option.

the first RAW file of the 4 is available in the RAW file using DCU. Just go to the Pixel-shift icon and select off. It's worth upgrading DCU to the laterst version (5.6.2)

MilesGreen

Link Posted 31/03/2017 - 07:24
RobL wrote:
pentaxian450 wrote:
Quote:
So, to freeze movement in PSR I assume that whatever shutter speed would normally suffice then divide by four: say 1/500 sec would require a setting of 1/2000 sec. If the ISO is increased by four stops to suit I wonder if the noise will cancel any benefit? Further experimentation needed.

Your assumption is wrong. You need the same speed in PSR as in a single exposure shot. The problem encountered in PSR is that the four pictures aren't taken at the same time, but one after the other. If there is any movement in between the different exposure, then you get some blur, the extent of it depending upon how much movement occurred in between the different exposures. To make things worst, when movement is caused by wind, light objects, or objects with low mass and high "drag" will move more than heavy or low "drag" objects.

I think you misunderstand me, I agree the exposure for PSR is the same as for a single shot but say you pick a speed of 1/500 then the timeframe for a PSR will be 1/125 sec (4x 1/500). In order to get a timeframe of 1/500 sec in PSR (4x 1/2000) you would need to adjust the ISO by four stops. This of course assumes that the interval between PSR exposures is instantaneous which may not be the case.

No the interval is longer than that. It takes about a second to complete the PSR captures, so about 0.25 seconds between exposures. That's enough to let the moon move.

Regarding exposure, you could switch spot-metering on in LV, that should let the camera do it correctly. Keep in mind that it's daylight on the part of the moon you're photographing. Think sunny 16 rule, or ISO 100, f/8, 1/250s for starters.

The moon is too fast at that focal length for PS (unless you have an equatorial mount).

davesexton

Link Posted 17/04/2017 - 15:55
RobL wrote:
Last night I took a few photos of the moon with a K-1 and 150-450mm lens at 450mm, and experimented with PSR. Here are a couple of examples at the same exposure of F16, 1/320sec ISO 100 cropped and boosted in Lighroom, first with PSR and the second without, both on a tripod with remote release and autofocus:



Whilst the PSR shot has a bit more detail there is a strange artefact on the periphery in the bottom left and top right quadrants, caused either by the camera shifting slightly on the mount or the motion of the moon in that brief moment of exposure. The same thing happened at different exposures, Any ideas?

What you are almost certainly seeing is refraction caused by the atmosphere that constantly causes the image to 'undulate' (the same effect is what makes the stars 'twinkle'). The amount of image movement due to atmospheric disturbance almost certainly exceeds the sensor movement used by Pixel Shift. This woudl be enough to give 'movement' artifacts when using Pixel Shift.
Capture: Pentax K-1, PENTAX HD PENTAX-D FA 24-70mm F2.8 ED SDM WR, PENTAX 100mm f/2.8 WR Macro, SAMYANG 14mm F2.8 ED AS IF UMC, SAMYANG 35mm F1.4 AS UMC, SAMYANG 85mm F1.4 AS IF UMC

Processing: Adobe Bridge for organisation, DxO Optics Pro Elite for RAW development, ON1 Photo RAW for some 'stylising' and Affintiy Photo for more involved edits.
Add a Comment
You must be registered or logged-in to comment.