A7R2 star eater at 4s?

Started 10 months ago | Questions
daran
daran Regular Member • Posts: 112
A7R2 star eater at 4s?
12

Playing with my shiny sharp 18mm lens on my A7R2, I was testing the amount of star trailing vs exposure time to find a good compromise for my next star gazing trip. What I expected, given some previous research, was best results to be around 5s to 8s @ISO 640. What I found instead was a huge discrepancy between shots >= 4 seconds and those <= 3.2s.

It looks suspiciously like the infamous "star eater" algorithm, but I expected that to happen with bulb mode (12 bit) or serial shots. Instead I seem to trigger the effect with normal shots, as soon as I go beyond 3.2 seconds per shot. I tried ISO100, ISO640, ISO6400, raw compressed or raw uncompressed, normal shot or timed shot or external trigger, CaptureOne 9 vs dcraw vs RawDigger. All resulted in the same amount of "eaten" stars for 4s shots when compared to 3.2s shoots at otherwise same settings. Firmware is 3.30.

This sure does look like I need to live with the algorithm and just shoot long enough to reduce the effect. Or am I missing some magic combination of settings to avoid this rubbish filter?

 daran's gear list:daran's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Sony FE 70-300mm F4.5-5.6 G OSS Zeiss Batis 18mm F2.8 Sony E 18-200mm F3.5-6.3 OSS +4 more
ANSWER:
Lightshow
Lightshow Veteran Member • Posts: 5,668
Re: A7R2 star eater at 4s?
2

Complain to Sony, complaining here will not change anything.

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daran
OP daran Regular Member • Posts: 112
Re: A7R2 star eater at 4s?
5

I'm here to learn, not to complain. Or at least that's what I prefer to believe.

 daran's gear list:daran's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Sony FE 70-300mm F4.5-5.6 G OSS Zeiss Batis 18mm F2.8 Sony E 18-200mm F3.5-6.3 OSS +4 more
Trollmannx Senior Member • Posts: 3,400
Re: A7R2 star eater at 4s?
4

The star eater issue is only a problen in bulb mode.

Exposures using camera settings up to 30 sec are NOT affected.

Use the bulb setting, and the spatial filtering is different - the star eater issue set in.

If exposing for 4 sec (setting the camera to 4 sec exposure) - no problem!

If using bulb mode AND exposing for 4 sec (or any other exposure) - viola - star eater issue!

The star eater issue is usually not much of a problem unless doing astrophotography with a star tracker and caring about the faintest stars - in ordinary photographic scenes the effect simply remove noise a bit aggresively - and the end result usually look a bit better with the the heavy filtering than without - just try for yourself!

Magnar W
Magnar W Senior Member • Posts: 1,822
Re: A7R2 star eater at 4s?
1

Photos, please!

D Cox Forum Pro • Posts: 17,644
Re: A7R2 star eater at 4s?

Trollmannx wrote:

The star eater issue is only a problen in bulb mode.

Exposures using camera settings up to 30 sec are NOT affected.

Use the bulb setting, and the spatial filtering is different - the star eater issue set in.

If exposing for 4 sec (setting the camera to 4 sec exposure) - no problem!

If using bulb mode AND exposing for 4 sec (or any other exposure) - viola - star eater issue!

The star eater issue is usually not much of a problem unless doing astrophotography with a star tracker and caring about the faintest stars - in ordinary photographic scenes the effect simply remove noise a bit aggresively - and the end result usually look a bit better with the the heavy filtering than without - just try for yourself!

Does this affect raw files, or only JPGs ?

daran
OP daran Regular Member • Posts: 112
Sample shoots

These are 400% crops highlighting the issue. What you are seeing is the Orion Nebula. The shots were taken on a tripod (using WIFI app to trigger). There was strong light pollution (big city). The crops were made with CaptureOne (v9) with all image improvements disabled. The crop areas were roughly aligned as the target moved between shots (ca 15°/hour). All shots were manual focus (once at beginning of series), ISO640, f2.8, IS disabled, LENR disabled, RAW.

3.2s

4.0s

4.0s

3.2s

 daran's gear list:daran's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Sony FE 70-300mm F4.5-5.6 G OSS Zeiss Batis 18mm F2.8 Sony E 18-200mm F3.5-6.3 OSS +4 more
daran
OP daran Regular Member • Posts: 112
Sample shoots - EXIF

This is the EXIF dump (using RawDigger) of one of the 4.0s shots.

-- hide signature --

ExifTool ----
ExifTool Version Number : 10.30
---- File ----
File Name : DSC04644.ARW
Directory : /Tests/2016 A7r2_18mm_time_series
File Size : 41 MB
File Modification Date/Time : 2016:11:23 02:25:28+01:00
File Access Date/Time : 2016:11:26 16:54:54+01:00
File Inode Change Date/Time : 2016:11:23 01:56:20+01:00
File Permissions : rwxrwxrwx
File Type : ARW
File Type Extension : arw
MIME Type : image/x-sony-arw
Exif Byte Order : Little-endian (Intel, II)
---- EXIF ----
Image Description :
Orientation : Horizontal (normal)
Image Width : 8000
Image Height : 5320
Bits Per Sample : 14
Compression : Sony ARW Compressed
Photometric Interpretation : Color Filter Array
Samples Per Pixel : 1
Planar Configuration : Chunky
X Resolution : 350
Y Resolution : 350
Resolution Unit : inches
CFA Repeat Pattern Dim : 2 2
CFA Pattern 2 : 0 1 1 2
Sony Raw File Type : Sony Compressed RAW
Strip Offsets : 330240
Rows Per Strip : 5320
Strip Byte Counts : 42560000
Preview Image Start : 137890
Preview Image Length : 190816
Y Cb Cr Positioning : Co-sited
Exposure Time : 4
F Number : 2.8
Exposure Program : Manual
ISO : 640
Sensitivity Type : Recommended Exposure Index
Recommended Exposure Index : 640
Exif Version : 0230
Date/Time Original : 2016:11:23 02:25:28
Create Date : 2016:11:23 02:25:28
Components Configuration : Y, Cb, Cr, -
Compressed Bits Per Pixel : 8
Brightness Value : -7.865625
Exposure Compensation : 0
Max Aperture Value : 2.8
Metering Mode : Multi-segment
Light Source : Cool White Fluorescent
Flash : Off, Did not fire
Focal Length : 18.0 mm
User Comment :
Flashpix Version : 0100
Color Space : sRGB
Exif Image Width : 7952
Exif Image Height : 5304
Interoperability Index : R98 - DCF basic file (sRGB)
Interoperability Version : 0100
File Source : Digital Camera
Scene Type : Directly photographed
Custom Rendered : Normal
Exposure Mode : Manual
Digital Zoom Ratio : 1
Focal Length In 35mm Format : 18 mm
Scene Capture Type : Standard
Contrast : Normal
Saturation : Normal
Sharpness : Normal
Lens Info : 18mm f/2.8
Lens Model : ZEISS Batis 2.8/18
Subfile Type : Reduced-resolution image
Make : SONY
Camera Model Name : ILCE-7RM2
Software : ILCE-7RM2 v3.30
Modify Date : 2016:11:23 02:25:28
Artist : Harald Schweder
Thumbnail Offset : 38916
Thumbnail Length : 2846
Copyright :
---- MakerNotes ----
Rating : 0
Brightness : 0
Long Exposure Noise Reduction : Off
High ISO Noise Reduction : Off
HDR : Off; Uncorrected image
WB Shift AB GM : 0 0
WB Shift AB GM Precise : 0.00 0.00
Face Info Offset : 94
Sony Date Time : 2016:11:23 02:25:28
Sony Image Width : 7952
Faces Detected : 0
Face Info Length : 37
Meta Version : DC7303320222000
Creative Style : Standard
Color Temperature : Auto
Color Compensation Filter : 0
Scene Mode : Standard
Zone Matching : ISO Setting Used
Dynamic Range Optimizer : Off
Image Stabilization : Off
Color Mode : Standard
Full Image Size : 7952x5304
Preview Image Size : 1616x1080
File Format : ARW 2.3.1
Quality : RAW + JPEG
Flash Exposure Compensation : 0
White Balance Fine Tune : 0
Sony Model ID : ILCE-7RM2
Multi Frame Noise Reduction : Off
Picture Effect : Off
Soft Skin Effect : Off
Vignetting Correction : Auto
Lateral Chromatic Aberration : Auto
Distortion Correction Setting : Auto
Lens Type : E-Mount, T-Mount, Other Lens or no lens
Lens Spec : E 18mm F2.8
Auto Portrait Framed : No
Flash Action : Did not fire
Focus Mode : Manual
AF Area Mode Setting : Flexible Spot
Flexible Spot Position : 328 260
AF Zone Selected : n/a
AF Points Used : (none)
Focal Plane AF Points Used : (none)
Focus Location : 7952 5304 3454 3502
Variable Low Pass Filter : n/a
RAW File Type : Compressed RAW
Flash Level : Normal
Release Mode : Normal
Sequence Number : Single
Anti-Blur : Off
Intelligent Auto : Off
White Balance : Cool White Fluorescent
Shot Number Since Power Up : 8
Sequence Image Number : 1
Sequence File Number : 1
Sequence Length : 1 file
Camera Orientation : Horizontal (normal)
Quality 2 : RAW + JPEG
Sony Image Height : 5304
Model Release Year : 2015
Ambient Temperature : 24 C
AF Area Mode : Manual
Focus Position 2 : 218
Camera Temperature : 29 C
Sony ISO : 636
Base ISO : 100
Stops Above Base ISO : 2.7
Sony Exposure Time 2 : 4
Sony Max Aperture Value : 2.9
Picture Effect 2 : Off
Distortion Correction : Applied
Lens Zoom Position : 0%
Battery Temperature : 32.8 C
Battery Level : 68%
Lens Mount 2 : E-mount
Lens Type 3 : Zeiss Batis 18mm F2.8
Camera E-mount Version : 1.60
Lens E-mount Version : 1.50
Lens Firmware Version : Ver.01
Tiff Metering Image Width : 44
Tiff Metering Image Height : 30
Tiff Metering Image : (Binary data 2640 bytes, use -b option to extract)
Release Mode 3 : Normal
Self Timer : Off
Flash Mode : Fill-flash
HDR Setting : Off
Picture Profile : Standard/Neutral - Gamma Still (PP2)
WB RGB Levels : 488 256 550
Min Focal Length : 18.0 mm
Flash Status : No Flash present
Image Count : 4762
Sony Exposure Time : 4
Sony F Number : 2.9
Image Count 2 : 4762
Sony Date Time 2 : 2000:00:00 00:25:25
Release Mode 2 : Normal
Internal Serial Number : 67ff0000e309
Lens Mount : E-mount
Lens Format : Full-frame
Lens Type 2 : Zeiss Batis 18mm F2.8
Lens Spec Features : E
Image Count 3 : 4762
SR2 Sub IFD Offset : 43378
SR2 Sub IFD Length : 56958
SR2 Sub IFD Key : 0x44332211
Black Level : 512 512 512 512
WB RGGB Levels : 2276 1024 1024 2264
Color Matrix : 1243 -205 -15 -31 1209 -154 47 -47 1024
WB RGB Levels Daylight : 2500 1024 1596
WB RGB Levels Cloudy : 2704 1024 1464
WB RGB Levels Tungsten : 1532 1024 2888
WB RGB Levels Flash : 2756 1024 1440
WB RGB Levels 4500K : 2252 1024 1800
WB RGB Levels Shade : 2984 1024 1316
WB RGB Levels Fluorescent : 2276 1024 2264
WB RGB Levels Fluorescent P1 : 2420 1024 1676
WB RGB Levels Fluorescent P2 : 2720 1024 1548
WB RGB Levels Fluorescent M1 : 1808 1024 2772
WB RGB Levels 8500K : 3144 1024 1244
WB RGB Levels 6000K : 2680 1024 1476
WB RGB Levels 3200K : 1712 1024 2500
WB RGB Levels 2500K : 1328 1024 3488
White Level : 15360 15360 15360
Light Falloff Params : 16 0 224 608 1152 1888 2784 3808 4864 5920 6944 7968 9088 10176 11200 12128 13056
Chromatic Aberration Corr Params : 32 896 896 768 768 768 640 640 640 640 640 512 512 512 512 512 640 -128 -128 -128 -256 -256 -256 -256 -128 -128 -128 0 0 128 128 128 256
Distortion Corr Params : 16 22 0 -31 -68 -119 -176 -243 -307 -376 -435 -489 -526 -552 -552 -528 -469
---- PrintIM ----
PrintIM Version : 0300
---- Composite ----
Aperture : 2.8
Blue Balance : 2.210938
CFA Pattern : [Red,Green][Green,Blue]
Focus Distance 2 : 7.12 m
Image Size : 8000x5320
Lens ID : Zeiss Batis 18mm F2.8
Megapixels : 42.6
Preview Image : (Binary data 190816 bytes, use -b option to extract)
Red Balance : 2.222656
Scale Factor To 35 mm Equivalent : 1.0
Shutter Speed : 4
Thumbnail Image : (Binary data 2846 bytes, use -b option to extract)
Circle Of Confusion : 0.030 mm
Field Of View : 90.0 deg
Focal Length : 18.0 mm (35 mm equivalent: 18.0 mm)
Hyperfocal Distance : 3.85 m
Light Value : -1.7

 daran's gear list:daran's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Sony FE 70-300mm F4.5-5.6 G OSS Zeiss Batis 18mm F2.8 Sony E 18-200mm F3.5-6.3 OSS +4 more
daran
OP daran Regular Member • Posts: 112
Sample shoots - EXIF difference

This is the difference in the EXIF data between a 3.2 and a 4.0 shoot.

4c4
< File Name : DSC04643.ARW
---
> File Name : DSC04644.ARW
7,9c7,9
< File Modification Date/Time : 2016:11:23 02:25:06+01:00
< File Access Date/Time : 2016:11:26 17:28:25+01:00
< File Inode Change Date/Time : 2016:11:23 01:56:17+01:00
---
> File Modification Date/Time : 2016:11:23 02:25:28+01:00
> File Access Date/Time : 2016:11:26 16:54:54+01:00
> File Inode Change Date/Time : 2016:11:23 01:56:20+01:00
31c31
< Strip Offsets : 317952
---
> Strip Offsets : 330240
35c35
< Preview Image Length : 179838
---
> Preview Image Length : 190816
37c37
< Exposure Time : 3.2
---
> Exposure Time : 4
44,45c44,45
< Date/Time Original : 2016:11:23 02:25:06
< Create Date : 2016:11:23 02:25:06
---
> Date/Time Original : 2016:11:23 02:25:28
> Create Date : 2016:11:23 02:25:28
48c48
< Brightness Value : -7.834375
---
> Brightness Value : -7.865625
78c78
< Modify Date : 2016:11:23 02:25:06
---
> Modify Date : 2016:11:23 02:25:28
81c81
< Thumbnail Length : 2686
---
> Thumbnail Length : 2846
92c92
< Sony Date Time : 2016:11:23 02:25:06
---
> Sony Date Time : 2016:11:23 02:25:28
137c137
< Shot Number Since Power Up : 7
---
> Shot Number Since Power Up : 8
152c152
< Sony Exposure Time 2 : 3.2
---
> Sony Exposure Time 2 : 4
158c158
< Battery Level : 69%
---
> Battery Level : 68%
172c172
< WB RGB Levels : 486 256 555
---
> WB RGB Levels : 488 256 550
175,176c175,176
< Image Count : 4761
< Sony Exposure Time : 3.2
---
> Image Count : 4762
> Sony Exposure Time : 4
178,179c178,179
< Image Count 2 : 4761
< Sony Date Time 2 : 2000:00:00 00:25:04
---
> Image Count 2 : 4762
> Sony Date Time 2 : 2000:00:00 00:25:25
186,187c186,187
< Image Count 3 : 4761
< SR2 Sub IFD Offset : 43218
---
> Image Count 3 : 4762
> SR2 Sub IFD Offset : 43378
221c221
< Preview Image : (Binary data 179838 bytes, use -b option to extract)
---
> Preview Image : (Binary data 190816 bytes, use -b option to extract)
224,225c224,225
< Shutter Speed : 3.2
< Thumbnail Image : (Binary data 2686 bytes, use -b option to extract)
---
> Shutter Speed : 4
> Thumbnail Image : (Binary data 2846 bytes, use -b option to extract)
230c230
< Light Value : -1.4
---
> Light Value : -1.7

 daran's gear list:daran's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Sony FE 70-300mm F4.5-5.6 G OSS Zeiss Batis 18mm F2.8 Sony E 18-200mm F3.5-6.3 OSS +4 more
Magnar W
Magnar W Senior Member • Posts: 1,822
For sure focus error!
1

I am sure that there is slight focus differences between the pictures. Both 4 sec images are a bit out of focus! No wonder that faint stars are smoothed out!

Also, turbulent air might make a huge difference at a few seconds of exposure, and so might variations in atmospheric haze between the frames.

No, these pictures do not prove any in-camera star eating image processing.

daran wrote:

These are 400% crops highlighting the issue. What you are seeing is the Orion Nebula. The shots were taken on a tripod (using WIFI app to trigger). There was strong light pollution (big city). The crops were made with CaptureOne (v9) with all image improvements disabled. The crop areas were roughly aligned as the target moved between shots (ca 15°/hour). All shots were manual focus (once at beginning of series), ISO640, f2.8, IS disabled, LENR disabled, RAW.

3.2s

4.0s

4.0s

3.2s

daran
OP daran Regular Member • Posts: 112
Sample shoots - blue crop
1

This is a strongly enhanced crop of the blue channel of a 4.0s shot (used dcraw). You are seeing the three stars near top center of the 400% crops of Orion. Or rather you can only guess at them. For me the tell-tale of star eating is that each star yields two identical pixel values right next to each other.

 daran's gear list:daran's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Sony FE 70-300mm F4.5-5.6 G OSS Zeiss Batis 18mm F2.8 Sony E 18-200mm F3.5-6.3 OSS +4 more
daran
OP daran Regular Member • Posts: 112
Re: For sure focus error!

Magnar W wrote:

I am pretty sure that there is sight focus differences between the pictures.

Both 4 sec images are fr sure a bit out of focus. No wonder that faint stars are smoothed out!

Also, turbulent air might make a huge difference at a few seconds of exposure, and so might variations in atmospheric haze between the frames.

Sure looks like being defocussed in the 4s shots. However I focused manually and only once at the start of a longer series of shots. First I increased the exposure time in minimal increments from 1s to 30s, then decreased back again to 1s. I repeated the test the next day with toggling between 3.2s and 4.0s and varying other parameters (trigger type and ISO). All these shots showed the same defocussed look for >=4.0s and much more distinctive stars for <=3.2s. That would be one hell of a coincidence to be repeatedly caused by atmospheric variations.

No, these pictures do not prove any in-camera star eating image processing.

I believe they do. Of course I'd also like to see someone else either verifying the problem or telling me how to avoid it.

 daran's gear list:daran's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Sony FE 70-300mm F4.5-5.6 G OSS Zeiss Batis 18mm F2.8 Sony E 18-200mm F3.5-6.3 OSS +4 more
Trollmannx Senior Member • Posts: 3,400
Re: Sample shoots - blue crop
1

daran wrote:

This is a strongly enhanced crop of the blue channel of a 4.0s shot (used dcraw). You are seeing the three stars near top center of the 400% crops of Orion. Or rather you can only guess at them. For me the tell-tale of star eating is that each star yields two identical pixel values right next to each other.

The star eater issue in bulb mode affect RAW files as well as JPGs.

The test is flawed.

Out of focus images trying to show something that is an issue only if:

1) Using first class optics

2) Focusing within a few microns.

Use a good lens, stop down to f/4 and get the stars in focus. Preferably use a star tracker. Expose with camera settings and in bulb mode and compare.

If the test is flawed magnifying the image do not prove very much! 

Magnar W
Magnar W Senior Member • Posts: 1,822
Re: For sure focus error!

daran wrote:

All these shots showed the same defocussed look for >=4.0s and much more distinctive stars for <=3.2s. That would be one hell of a coincidence to be repeatedly caused by atmospheric variations.

Checked what might cause focus shift? Maybe you touched the focus ring a tad while handling the camera? Are the 4 sec pictures are taken later, so that temperature could have made a difference? Just a few degrees in temperature might cause focus shift.

From what I can see, the amount of light hitting the frame is about the same for all exposures, except that the stars are more out of focus for the 4 sec shots - the light discs are more spread - more out of focus!

Repeate the test! If I get clear skies within a few days, I will do some tests too.

daran
OP daran Regular Member • Posts: 112
Re: For sure focus error!

Magnar W wrote:

daran wrote:

All these shots showed the same defocussed look for >=4.0s and much more distinctive stars for <=3.2s. That would be one hell of a coincidence to be repeatedly caused by atmospheric variations.

Checked what might cause focus shift? Maybe you touched the focus ring a tad while handling the camera? Are the 4 sec pictures are taken later, so that temperature could have made a difference? Just a few degrees in temperature might cause focus shift.

I'm aware of focus shift, due to temperature or otherwise. My first test series (as shown in the crops) was: many fast -> many slow -> many fast:

The second night I was more specific and made two series (again manual focus once before a series):

So far each shot confirming the correlation that all shots >=4s have eaten stars, whereas faster shots don't. At this point I seriously doubt an analog problem could cause the observed behaviour.

From what I can see, the amount of light hitting the frame is about the same for all exposures, except that the stars are more out of focus for the 4 sec shots - the light discs are more spread - more out of focus!

A star in a defocussed image should have the same total amount of light recorded, just more spread among neighbouring pixels. It's difficult to tell with the noisy background in these images,but I do think that this is the case here.

Repeate the test! If I get clear skies within a few days, I will do some tests too.

Please do! Looking forward to you results.

 daran's gear list:daran's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Sony FE 70-300mm F4.5-5.6 G OSS Zeiss Batis 18mm F2.8 Sony E 18-200mm F3.5-6.3 OSS +4 more
daran
OP daran Regular Member • Posts: 112
Re: Sample shoots - blue crop

Trollmannx wrote:

daran wrote:

This is a strongly enhanced crop of the blue channel of a 4.0s shot (used dcraw). You are seeing the three stars near top center of the 400% crops of Orion. Or rather you can only guess at them. For me the tell-tale of star eating is that each star yields two identical pixel values right next to each other.

The star eater issue in bulb mode affect RAW files as well as JPGs.

I have no interes in JPGs so didn't try.

The test is flawed.

Out of focus images trying to show something that is an issue only if:

1) Using first class optics

Test were done with a Zeiss Batis 18mm. Does that qualify?

2) Focusing within a few microns.

While manual focusing at night is tricky, it can be done using patience and 12x zoomed live view. But had I missed the focus, it surely should have affected 3.2s and 4.0s exposures alike?

Use a good lens, stop down to f/4 and get the stars in focus. Preferably use a star tracker. Expose with camera settings and in bulb mode and compare.

Currently there is no gap between the clouds, so further tests have to wait.

If the test is flawed magnifying the image do not prove very much!

 daran's gear list:daran's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Sony FE 70-300mm F4.5-5.6 G OSS Zeiss Batis 18mm F2.8 Sony E 18-200mm F3.5-6.3 OSS +4 more
JimKasson
JimKasson Forum Pro • Posts: 12,754
Re: A7R2 star eater at 4s?

daran wrote:

Playing with my shiny sharp 18mm lens on my A7R2, I was testing the amount of star trailing vs exposure time to find a good compromise for my next star gazing trip. What I expected, given some previous research, was best results to be around 5s to 8s @ISO 640. What I found instead was a huge discrepancy between shots >= 4 seconds and those <= 3.2s.

It looks suspiciously like the infamous "star eater" algorithm, but I expected that to happen with bulb mode (12 bit) or serial shots.

12-bit precision is not the cause of star-eating. Spatial filtering is.

http://blog.kasson.com/?p=11542

Instead I seem to trigger the effect with normal shots, as soon as I go beyond 3.2 seconds per shot.

Timed shutter operation up to 30 seconds does not invoke spatial filtering.

Bulb operation, regardless of the actual shutter opening duration, does.

LENR does not by itself cause spatial filtering to happen.

Jim

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daran
OP daran Regular Member • Posts: 112
Re: A7R2 star eater at 4s?

JimKasson wrote:

daran wrote:

It looks suspiciously like the infamous "star eater" algorithm, but I expected that to happen with bulb mode (12 bit) or serial shots.

12-bit precision is not the cause of star-eating. Spatial filtering is.

http://blog.kasson.com/?p=11542

Instead I seem to trigger the effect with normal shots, as soon as I go beyond 3.2 seconds per shot.

Timed shutter operation up to 30 seconds does not invoke spatial filtering.

The discussion around https://www.dpreview.com/forums/thread/3837369?page=2 and generally the tests you published in your blog are what had me not expecting to see any spatial filtering (hot pixel suppression or otherwise) in my test sets. I don't know how or why this did not show up during your tests. And admittedly I'm only 90% positive about my interpretation of my test.

Still, empiric results trump generic wisdom. My tests seem repeatable and analog causes seem at least unlikely. To recap:

- the effect is easily noticeable in 100% crops

- the effect can be triggered at will by toggling between 3.2s and 4.0s shoots

- in the longer shoots the maximum intensity pixel is reliably lower than in the shorter shots

- 1s, 1.3s, 1.6s, 2.5s, 3.2s are not showing the effect

- 4s, 5s, 6s are showing the effect to similar degree

- 8s and above are hard to tell, due to star trailing setting in

- multiple tests on two different days confirmed the effect, so far with 100% reliability

- ISO setting does not effect the result

- using an external trigger does not effect the result

- using uncomressed RAW does not effect the result

- bulb mode has not been tested

- apparent movement of the sky with respect to the bayer matrix can not be the issue, as stars are affected all over the place

- temperature, seeing conditions or other focus drifts can not explain the repeatability

The provided crops could still be coincidental, but I have repeated the tests and checked other areas, not just the provided crops. I'd be happy to provide the RAWs. I'd very much like someone to confirm or reject my observation with independent tests.

Harald

 daran's gear list:daran's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Sony FE 70-300mm F4.5-5.6 G OSS Zeiss Batis 18mm F2.8 Sony E 18-200mm F3.5-6.3 OSS +4 more
JimKasson
JimKasson Forum Pro • Posts: 12,754
Generic wisdom?

daran wrote:

JimKasson wrote:

daran wrote:

It looks suspiciously like the infamous "star eater" algorithm, but I expected that to happen with bulb mode (12 bit) or serial shots.

12-bit precision is not the cause of star-eating. Spatial filtering is.

http://blog.kasson.com/?p=11542

Instead I seem to trigger the effect with normal shots, as soon as I go beyond 3.2 seconds per shot.

Timed shutter operation up to 30 seconds does not invoke spatial filtering.

The discussion around https://www.dpreview.com/forums/thread/3837369?page=2 and generally the tests you published in your blog are what had me not expecting to see any spatial filtering (hot pixel suppression or otherwise) in my test sets. I don't know how or why this did not show up during your tests. And admittedly I'm only 90% positive about my interpretation of my test.

Still, empiric results trump generic wisdom.

Are you saying my testing is generic wisdom? I used different conditions from yours, but my tests are also repeatable.

Compared to yours, my testing has the advantage of:

  • not relying on focusing accuracy
  • not relying on repeatable atmospheric effects
  • not needing a lens at all, and thus taking the lens characteristics out of the, ahem, picture
  • providing quantitative results

Now, I am not discounting your results. I'm just saying that, unless your camera works differently from the ones that I tested -- and, through the magic of firmware, that could indeed be the case -- what you're seeing is not the result of spatial filtering.

If you have the ability to do Fourier analyses of dark-field images, you could repeat my tests.

If you use Matlab, I could send you the code.

My tests seem repeatable and analog causes seem at least unlikely. To recap:

- the effect is easily noticeable in 100% crops

- the effect can be triggered at will by toggling between 3.2s and 4.0s shoots

- in the longer shoots the maximum intensity pixel is reliably lower than in the shorter shots

- 1s, 1.3s, 1.6s, 2.5s, 3.2s are not showing the effect

- 4s, 5s, 6s are showing the effect to similar degree

- 8s and above are hard to tell, due to star trailing setting in

- multiple tests on two different days confirmed the effect, so far with 100% reliability

- ISO setting does not effect the result

- using an external trigger does not effect the result

- using uncomressed RAW does not effect the result

- bulb mode has not been tested

- apparent movement of the sky with respect to the bayer matrix can not be the issue, as stars are affected all over the place

- temperature, seeing conditions or other focus drifts can not explain the repeatability

The provided crops could still be coincidental, but I have repeated the tests and checked other areas, not just the provided crops. I'd be happy to provide the RAWs. I'd very much like someone to confirm or reject my observation with independent tests.

Harald

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daran
OP daran Regular Member • Posts: 112
Sample shoots - artificial star
3

For this test an artificial star (ca 50µm light source) was placed about 50m from the camera. All shots were repeated (for verification) and no focusing happened between test pairs. Exposures were started in Timer mode. ISO100, IS off, LENR off, RAW.

Sony 55mm, 4s, f5.6

Sony 55mm, 3.2s, f5.6

Zeiss Batis 18mm, 3.2s, f8, exposure +3

Zeiss Batis 18mm, 4s, f8, exposure +3

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