Opinions on my purple sensor cast

[arkid]

Hi all.    I've got a purple cast on the bottom of my sensor in my a7s2.   It isn't really noticeable if you use conservative ISO levels (say below 10,000) but at around 12,800 or above I can start to see this purple haze at the bottom of images.  

 

So some quick examples, first of a night sky at 12800,16000 and 20000 ISO...

 

http://ulterior-motive.com/shared/a7s2/iso-12800.jpg

http://ulterior-motive.com/shared/a7s2/iso-16000.jpg

http://ulterior-motive.com/shared/a7s2/iso-20000.jpg

 

 

And a few ISO's hgiher, 25600 and 40000 ISO

 

http://ulterior-motive.com/shared/a7s2/iso-25600-dog.jpg

http://ulterior-motive.com/shared/a7s2/iso-40000-dog.jpg

 

To clarify, this doesn't seem to be light leaks as I've tried back tape.  I have the camera on default colour profiles and nothing unstandard configured.

 

Are others seeing this at such ISO levels ?   Anyone want to go shoot a shot or two into the night sky to check ?

[Guest Jaf-Photo]

I use ISO 100 for 90% of my shots. 0% of my shots are above ISO 1600. So I have no idea what you are writing about but my tip would be to learn exposure.

[arkid]

I use ISO 100 for 90% of my shots. 0% of my shots are above ISO 1600. So I have no idea what you are writing about but my tip would be to learn exposure.

Thanks Jaf-Photo, that's the most unhelpful answer I've ever had to a question I've posted on a forum.  

 

Anyone else that's actually got an A7S2 and uses it at the high ISO's its designed for got a response?

[tinplater]

What is interesting to me is that I can't make out the "haze" .  I guess that is the one advantage of being 74 and needing cataract surgery.  The image of your dog must have been taken in essentially total darkness..amazing technology.  I can't help since I too only rarely shoot above ISO 3200 with my A7rii.

[Guest all8]

It looks a little bit like Amp Glow (google a7s amp glow for lots of discussion on the topic). Hard to say if it is normal or not, at least compare against the images from others first ... before contacting Sony to see if the camera has a defect.

 

Using Noise Reduction might help, at least for longer exposures the camera takes a second exposure with the shutter closed and "subtracts" the noise. At least that is how it works on the A7ii. Astro photographers do a similar thing to remove this kind of noise (which comes from high ISO and heat I believe).

[Guest Jaf-Photo]

To learn exposure is the most helpful tip you will get on this forum and anywhere.

 

I still can't believe people who spend thousands of euros on cameras but plainly refuse to learn how they work.

 

If you actually knew how ridiculous ISO 12800 is, you would blush.

 

Thanks Jaf-Photo, that's the most unhelpful answer I've ever had to a question I've posted on a forum.

Anyone else that's actually got an A7S2 and uses it at the high ISO's its designed for got a response?

[Username]

An A

 

I still can't believe people who spend thousands of euros on cameras

but plainly refuse to learn how they work.

If you actually knew how ridiculous ISO 12800 is, you would blush.
 

  

You're way off base. An a7S-II is barely ticking over at ISO

6400. IOW, 12800 is just off of idle. It's made to chug along 

at 6-digit ISO without missing a beat. AAMOF, it's inferior at 

low and middle ISOs compared to normal sensors. There's 

no sense, none, in using an a7S-II at ISO 100. Get with it :-( 

[Guest Jaf-Photo]

If you cannot grasp all the bad things that happen to an image when you use a faint light source and amplify it many many times over and then apply image "enhancing" software, you should be ordered by a federal judge to only shoot at ISO 100 for a full year. That should set you straight

[arkid]

If you cannot grasp all the bad things that happen to an image when you use a faint light source and amplify it many many times over and then apply image "enhancing" software, you should be ordered by a federal judge to only shoot at ISO 100 for a full year. That should set you straight

 

Jaf, this post was a straight forward question asking others with an a7s2 if they experience purple casting at the same iso levels I'm reporting.   If this was a general post about isos and image quality your comments would be relevant but there totally irrelevant to this post.   

 

I've used "normal" iso sensitivity cameras for 20+ years, the majority of that time film cameras...  is that acceptable?  Surprisingly the first camera I bought was not an a7s2.

[Guest Jaf-Photo]

Before replying to the OP I checked a number of images from the A7SII shot at ISO 12800. They did not have acceptable image quality to me. So the obvious answer is to do the normal things. Use a tripod and a fast lens and find the optimal settings for whatever light you have available. I.e. use the craft of photography instead of cranking the settings the h€ll up on the camera.

 

Jaf, this post was a straight forward question asking others with an a7s2 if they experience purple casting at the same iso levels I'm reporting.   If this was a general post about isos and image quality your comments would be relevant but there totally irrelevant to this post.   

I've used "normal" iso sensitivity cameras for 20+ years, the majority of that time film cameras...  is that acceptable?  Surprisingly the first camera I bought was not an a7s2.

[Username]

Before replying to the OP I checked a number of images from the A7SII

shot at ISO 12800. They did not have acceptable image quality to me.

So the obvious answer is to do the normal things. Use a tripod and a fast

lens and find the optimal settings for whatever light you have available. I.e.

use the craft of photography instead of cranking the settings the h€ll up on

the camera.

 

   

The a7S-II is a purpose-built mega-ISO device. Like any device 

it's not perfect, but it excels at its intended purpose, a purpose 

to which other cameras should hardly be put. You "advice" is all 

about all those other cameras. Essentially your "advice" says to  

"Rethink your purpose. Become an ISO 100 geek, and use an 

ISO 100 camera. Abandon your a7S-II and the art of ultra-low 

light photography, and join the pixel peeping herd."  

 

Nobody gives a ratzazz about what you might have found when

you compared geeky squeaky clean ISO 100 images to output 

of an a7S-II at 5 or 6 digit ISO settings. There is nothing useful 

to be determined by such comparisons. Stunning differences,

yes. But useful ? Not in the least. Just compare ISO 204,800 

output from the a7S-II to the ISO 25,600 output of your beloved 

hi-rez low-ISO camera. Then you WILL see not only a stunning 

difference, but a USEFUL difference ... at least useful to those 

who need to work in very dim light.   

   

There is, for some, an actual NEED to work in dim light. It's just 

their working conditions. There is, for no one, any actual NEED

to make pixel-peeper ISO 100 images. It's just a hi-tech hobby. 

[Guest Jaf-Photo]

I don't give a fugg. The laws of light are still the same.

[Guest all8]

In your account settings ... add to Ignore Pref's list ... problem goes away.

 

 

Just saying ...

[mttdxb]

Just to put some constructive idea into this thread ... and I dont have the A7S2 either for testing.

 

The images you posted all show the "purple haze" from the bottom up.  What happens if you take the same image (or under same conditions) with different orientation of the camera? Portrait vs Landscape vs 180 degree tilt Landscape?

Does the haze still show bottom up only on all 3 images?

 

If it would be a sensor or light leak problem, the haze should appear in the same segment of the sensor, rather than the taken image and move around the subject. (if you can follow my thoughts...)

 

In case the haze remains static on the taken image, then I assume there is a very faint light source somewhere from that direction which the human eye cant pick up but is recognized by the sensor? You might wanna try to adjust color

temperature to see if the haze changes color which would point to the same direction. 

[Guest Jaf-Photo]

Thank you. Perfect solution to your spamming.

 

In your account settings ... add to Ignore Pref's list ... problem goes away.

 

 

Just saying ...

[Username]

I don't give a fugg. The laws of light are still the same.

   

+1  

 

Very solid !