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Ben

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Ben last won the day on January 5 2017

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  • Birthday 09/15/1982

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  1. This recent Article on philipreeve.net might hold some insights that could help you. https://phillipreeve.net/blog/adapters-manual-lenses-sony-a7-series-guide/ In regard to the length of the adapter the following illustration from the article is most comprehensive why these adapters not only need to make a physical connection of different bayonet standards but must also maintain the proper distance to the projection plane. If the adapter is too long, you lose the ability to focus on a target at infinity and if it is to short, you decrease the close focus ability. Both errors push the lens in directions for which it hasn't been designed/optimized for.
  2. I do not think that bias frames are meant to counter hot / dead pixels. AfaIk they are meant to compensate for artificially added values that are added between exposure and raw file writing by the firmware. Some manufacturers do this to keep the look of the files consistent throughout the ISO ranges by effectively in- and decreasing the blackpoint of the data. But in general DSS can handle many calibration frames for each stack - be it flat, dark or bias. You can configure in what way the sets of calibration frame types are stacked, too(usually you do not want to emphasize rejection here and choose average). DSS creates a master calibration frame for every category of calibration frame. So yes you can take a lot of flat frames to calibrate the vignette and dust spots, as well as dark frames to counter the general electronic noise (which encompasses hot and dead pixels), as well as bias frames to calibrate for a proper black point of your data (which is mostly needed for scientific purposes). Your results look really lovely. If you want to do something about the color cast of the pictures You will soon see that fiddling around with white balance has some bad effects. Working with subtract layers is a way better approach when you want to counter effects like city glow or other light pollution. This can also work with gradients and masks. It can however get very tedious. I hope to see more of your night city scapes
  3. I am glad you are making progress. Short explanation about the different modes in which stacking programs work. Average(DSS), Mean(Photoshop): creates the mathematical mean value which adds all values and divides it by the number of frames. This method yields the best results for reducing noise and even increases accuracy(effective bit depth). But every outlier will influence the final outcome. I think outliers will not influence your result because you have nothing you want to filter out. Median (DSS, Photoshop): creates the statistical mean value which puts all pixel values in an ordered line and takes the center one. This method is perfect for rejecting outliers. In your case on a long enough acquisition phase would filter out the car lights and produce an image with only the things in the frame that are visible most of the time. Maximum (Photoshop), lighten (star stax): creates the statistical maximum and puts all values in an ordered line and takes the brightest one. This method is good for starstreaking but bad for noise as hot and stuck pixels are usually the brightest ones. There are some advanced stacking methods like sigma-kappa clipping but those are only useful for weighting rejection in a meaningful way. I would stick to stack with median/average in your scenario. Regards, Ben
  4. What timde said. bulb exposures is really not the strong suite of the A7rII. Due to the nature of bsi sensors there is more crosstalk noise in the recorded data. I haven't done a lot with dark frames yet but in my experiences they did not help too much with the noise. In more astrophotography related forums I got the advice that dark frames only show a good effect if you take a lot of them and average - so 3 frames might just not cut it. There has however been some cases were the stuck/dead pixel map that the camera generates from time to time when you turn it off - was not properly triggered by the chron-job of the firmware. One thing you could try is to set the camera's internal date ahead in time for like 2 years or something, turn the camera off and hope that it takes the calibration exposure with shut curtain. Resetting the date to the actual time won't delete the stuck/dead pixel map. My camera seems to take this exposure roughly every 2 weeks when I turn it off. Hope that helps, Ben
  5. Hi, here is a good resource for metabones performance with many lenses: http://briansmith.com/sony-a7rii-canon-ef-smart-adapter-tests/ My recently aquired Canon 300/2.8 L USM 1st gen (no is) works very well with the metabones IVt in green mode on the A7rII. I have yet to test the advanced mode but I intend to write a longer post about this combination. Regards, Ben
  6. Hi, If you want to assess the image quality impact you could just put it on a tablet with a white background in aperture priority and stop down until you see an impact on iq. Just make sure you test different focussing distances and focal lengths. May be it is not visible at all or may be only stopped down to something beyound F16. That at least gives you confidence about the extend of the issue. You could also try to see if pumping between 24 and 70mm moves enough air inside the lens that it might move the spec. Good luck!
  7. The Witch Head Nebula Acquisition details: 110 x 30 sec subs @ ISO1600 f4.5 1 x flat frame Nikon Ai ED IF 300/4.5 lens Sony A7rII Skywatcher - Star Adventurer with counter weight Shot in rural Germany (bortle 6/7) on 29th of December 2016 from 2000h to 2150h I was happy to see some nebula details until I saw the NASA version. Focus was slightly off and I think that is the reason I was not able to bring out better star colors. The lateral chromatic aberrations mixed with the actual star color to form one single and false color disc. I hope you like it despite my errors in the field.
  8. The Pleiades Acquisition details: 140 x 30 sec subs @ ISO1600 f4.5 1 x flat frame Nikon Ai ED IF 300/4.5 lens Sony A7rII Skywatcher - Star Adventurer Shot in star park Eifel @ Vogelsang - Germany (bortle 5) on 30th of December 2016 from 1910h to 2220h
  9. Ben

    Orion

    This looks very promising. Please post your final result once you manage to pull of a stack from raw files. The 70-200gm with the 2x extender seems to be very good for astro(at least much better than my 170€ Nikon ai 300/4.5 ed if). Did you stop down on top of the implicit 2 stop loss of the 2x extender or is this as wide open as you can go with this combination?
  10. I think you make this feature request sound more trivial than it actually is. I know that it has been done before by ie Nikon, but basically a downsized raw file is no raw file anymore. Resizing breaks the Bayer grid distribution that makes raw files interpretable by raw developers. It would however be nice to have higher bitrate saving options than jpeg.
  11. Ben

    Orion

    This very picture was acquired with a Nikon D750 and a 50/1.5 piggy backing the same mount(shutter shock was no issue). In my experience the Star adventurer can handle up to the advertised 10 pounds, iirc. But I must add that I use the 1kg counter weight and try to balance my gear in all axis. I made up to 90 second exposures at 500mm that showed no sign of trailing on a really flimsy tripod. Maybe I have a good copy but aside from that you could try: checking the batteries balance each axis mind ground vibrations from streets, or walking near the tripod mind the wind at the spot sandbagging your tripod If nothing helps and your periodic error is still visible with good polar alignment in 30 sec exposures or shorter, I would try to get a refund.
  12. Ben

    Orion

    Thank you I used a lent Alta Vanguard (http://www.vanguardworld.us/photo_video_us/alta-pro-263at.html). But I haven't had any troubles getting steady shots with my old aluminum tripod either. I use the timelapse app (which disables IBIS) to capture all sub exposures and during stacking they get a score depending on how many stars were found. It is easy to remove bad frames that way. But it is mostly the first frame or the last that I have to disregard. BTW, I can only recommend staying below firmware 3.3 for now. Sony enabled the low pass spacial filter a.k.a. the star eater algorithm to all exposures longer than 3.2 seconds. Prior to this update it was only a Problem in Bulb mode or other 12 bit modes. See http://blog.kasson.com/?p=16472 Unfortunately I already upgraded.
  13. I installed it from https://sony-pmca.appspot.com/apps via safari on mac os on the a7r2 and it was rather self explanatory. Did you use this browser method or from source? What OS do you run?
  14. Ben

    Orion

    Details on the shot: This shows part of the Orion constellation, a rather busy part of the northern hemisphere winter night sky. You can see 4 signature nebulas horsehead, running man, orion and the flame nebula. I tried to bring out the fainter interstellar dust lanes but succeeded only in parts due to shooting only from a bortle 6/7 region. I used the A7rII with an adapted Nikon 300/4.5 Ai Ed IF from the late seventies on an equatorial tracking mount (Star Adventurer). The stack, that is the basis of this image, consists of 197 x 30sec exposures and 1 flat frame (a calibration frame to counter the vignette). It was combined using sigma-kappa clipping method in deep sky stacker. This method is a good compromise between rejecting outliers (like planes or satelites) and increasing the precision. I had to do a rather fiddly post processing from there since the picture contains an enormous dynamic range. After stretching the image to a base line that had light pollution removed and realistic colors, I branched into 3 different versions of the image to make sure that the stars, the nebulas and the dust lanes came out properly. The dust lanes needed the biggest push and I also enhanced them with the tonal contrast filter from nik-color efex. In the end I masked everything together in Photoshop.
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