Modding the Sony A7S

[MarkS]

Tonight I modded the Sony A7S and it's still working!  Warranty is probably invalidated, though

There are two internal filters, both of which I removed to make it full spectrum.  The first filter is clipped onto the sensor and is also used for the piezo dust removal.  The second filter is bonded to the sensor with some kind of sticky stuff.

For those interested, the spectral responses can be deduced from these response curves produced from my home-made spectrograph (a long cardboard tube with a slit at one end and a diffraction grating + modded Canon 350D at the other)






Looking at those curves I think there is a very good argument for leaving Filter 1 in place because it seems to have a similar passband to a Baader IR/UV filter.

H-alpha has a wavelength of 656nm and the above chart suggests that modding the A7S has improved the H-alpha response by a factor of 5 or 6.

Later daytime tests with an H-alpha filter confirmed that the mod has increased H-alpha sensitivity by a factor of 5.5

Mark

[Carole]

I thought you had decided against modding the Sony A7S because it was a "star eater". 

The second filter is bonded to the sensor with some kind of sticky stuff.

How did you manage to remove the 2nd filter?

Carole

[MarkS]

I thought you had decided against modding the Sony A7S because it was a "star eater". 
How did you manage to remove the 2nd filter?

I did an interesting test on the star eating algorithm - see here:
http://www.dpreview.com/forums/post/55734616

There is a workaround, when needed, by sticking to programmed 30sec exposures (the A7S copes well with short exposures) instead of Bulb mode.

I very carefully prised up the corners and edges of the 2nd filter to remove it.

Mark

[Carole]

You mean you are only going to do 30sec exposures with this camera?

Looking at your test results, there is practically nothing to see with the naked eye between the two images.  I would have thought the benefits would far outweigh the disadvantages in any case. 

Looking forward to watching your progress. 

Carole

[MarkS]

I doubt if I will do 30sec exposures all the time because it involves a lot of processing.  But certainly when I'm doing variable star work, spectroscopy etc.

Look at the amount of copper used inside the camera - both on the back of the sensor (lower part of the image) and behind the other circuitry (top part of the image).  This ought to conduct heat away quite efficiently and probably helps to account for the very low thermal noise.



It also opens up the possibility of easily attaching more copper to enable external cooling

Mark

[JohnP]

U are one brave man.... that's all I can say....

Looks like really promising results though - 5X sensitivity improvement is impressive... will be really interesting to see what you get deep sky wise with 30 sec exposures given the sensitivity before you modded it especially at lower than F8..

John

[ApophisAstros]

and if it doesnt work mark, you`ve got a rocket propelled grenade launcher!!!!!!!!!!!  

roger

[The Thing]

Try this mod. A bit extreme but cooking on gas and very cool.

[MarkS]

Now that really is a serious mod!

Mark