Testing Sony A7S for leaks and internal LEDs

[Andy Perrin]

My Sony A7S does not appear to have any internal LEDs. I tried wrapping the entire camera in aluminum foil, putting the cap on the camera with no lens, and exposing for 2 minutes (121 sec) at ISO51200, which is the highest ISO I ever use in practice.

 

Result:

 

It did have a light leak though. ISO51200 at 62 sec, without foil:

[dabateman]

Thats an excellent photo of a black cat in coal mine.

 

The Sony A7s is on the list as not having IR problem. I am glad you confirmed it. I was once considering that camera for monochrome. But monochrome imaging has dramatically increased the price for conversion.

[Andy Perrin]

You are 100% incorrect, dabateman, that was a photo of bat in its bat cave!

[Stefano]

...or maybe a starry sky?

[Andy Perrin]

...or maybe a starry sky?

Nah, there are no green stars.

[Avalon]

  Hello. I want to convert A7s to full spectrum. Did you replace the IR-cut filter with a glass window and what was the filter size?  

[colinbm]

1 hour ago, Avalon said:

  Hello. I want to convert A7s to full spectrum. Did you replace the IR-cut filter with a glass window and what was the filter size?  

Quartz or fused silica would be recommended.

[ulf]

2 hours ago, colinbm said:

Quartz or fused silica would be recommended.

An alternative could be to just remove the filter and recalibrate the sensor position. That is how my A7III was modified.

Transmission-wise that is even better. There are some optical glass materials that have good enough transmission for most UV.

Coatings on the sensor cover window will then be the limiting factor.

 

There are advantages and disadvantages with either conversion method.

 

Window replacing the IR-filter and dust shaker filter:

+ If you get a window with exactly the same optical path length as the filters you replace there is no displacement ot the sensor. 

   You might want to adjust the position for some specific lens to focus correctly in UV or IR anyhow. This is mainly important for reaching infinity and more so for wide-FL lenses.

   If you can live with sacrificing the ability to reach infinity it might be OK to not do this adjustment

-  Any added glass with or without coating will limit the transmission of UV to the sensor. You have to chose a suitable material to avoid that.

- A window of suitable thickness, dimensions and materials might be difficult to find if you want to do the conversion yourself.

+ Dust on the outside surface of the replacement window is a bit away from the sensor pixels just as it is the stock camera.

- Dust can be trapped on the rear surface of the the replacement window and on the cover-window, bonded on the sensor, during conversion. That dust will be sealed in and not possible to clean without redoing the conversion.

- There are more air to glass surfaces that can cause internal reflections and goast images. A stock camera have advanced coatings on the filters designed to decrease this in the VIS.

-  Modern lenses are designed expecting some optical filter thickness in the camera. Some might loose performance, but they anyhow are often not that good in UV and IR.

 

Just removing the IR-filter and dust shaker filter:

-  More adjustment is needed for correct infinity focus during the conversion.

-  Without a replacement window, sensor dust is more close to the actual sensor pixels, making it visible earlier at wider aperture settings.

+  Without a replacement window any sensor dust will be directly reachable and easy to remove.

+  Older good lenses designed for film can sometimes preform better without any filter or replacement window.

+  No added windows that affect the transmission.

 

I am myself biased to the Remove method as it is how my second FS camera the A7III is modified.

Optically it is a more simple solution with for me less drawbacks. 

 

Cleaning the sensor properly is quite easy and not that expensive when you have learned how to do and have the right tools.

Normally I need just one sensor swab and a few drops of cleaning fluid. A swab costs ca €3.

As I'm a pixel peeper, I check and if needed clean the sensor before any serious photo session. A 5-10 minute jobb.

 

[Avalon]

  Well glass such as BK7 doesn't block UV-A and the window is pretty thin, lens will block much more. Another issue is that the sensor window can get accidentally scratched or even broken, which is why I'm thinking about using replacement window. 

 

I see on my A7s IR LED glow even when not modified. 

[ulf]

1 hour ago, Avalon said:

  Well glass such as BK7 doesn't block UV-A and the window is pretty thin, lens will block much more. Another issue is that the sensor window can get accidentally scratched or even broken, which is why I'm thinking about using replacement window. 

 

I see on my A7s IR LED glow even when not modified. 

You're right that a thin BK7 will not harm UV-A. You will just lose around 9% in surface losses and risk some more internal reflections that might cause flare.

 

I thought you might be interested in exploring some UV-B too as the older A7 models likely have surface coatings that are not blocking that much just as Stefano is doing with his early Canon M. I think his camera is modified without any replacement window. 

 

A replacement window will indeed protect the sensor window if you risk poking at it with something scratchy and hard.  

So far after 4 years of using my A7III and cleaning the sensor many times I have been fortunate to see it without any trace of scratches or wear.

I might just have been lucky. ;-)

 

If you do your sensor cleaning correctly there is nothing hard enough to harm the window or it's coating.

The sensor in my camera is only ever exposed during lens changes or cleaning.

 

What scenario do you see more to scratch the sensor window?

[Andy Perrin]

My A7S has no IR LED that I have seen? Mine is the original A7S. I have heard that the II and III have the LEDs. 
 

I had Lifepixel do their standard full spectrum conversion which uses some unknown glass that cuts at 280nm (50% transmission). The coating on the A7S sensor starts blocking well before then, so it’s not like you gain much by omitting the glass, except maybe less flare and the 9% reflection losses from the two interfaces. 

[Andy Perrin]

1 hour ago, ulf said:

the older A7 models likely have surface coatings that are not blocking that much

Unfortunately I think that is incorrect for the A7S. It is true for A7iii. 

[dabateman]

This is a screen grab from Vivek Lyer's data on the Sony cover glass.

The A7 is the best, but A7S isn't the worst. Sony started adding antireflective coatings to the coverglass to reduce reflections, for better images in visible light. But it does impact our UV images.

[Andy Perrin]

It may not be the worst, but it’s definitely zero by 300nm, so a glass that cuts at 280nm does no harm. 

[Avalon]

Glass lens alone will block far more UV than thin window glass unless it contains impurities. Do visible spectrum AR multi coatings (such as purple, blue or green reflecting) significantly block UV-A? Light loss due to reflections can be also bad.  Does Sony A7s mark I contain a self cleaning sensor mechanism which would stop working after IR-cut filter removal? 

 

[ulf]

25 minutes ago, Avalon said:

Glass lens alone will block far more UV than thin window glass unless it contains impurities. Do visible spectrum AR multi coatings (such as purple, blue or green reflecting) significantly block UV-A? Light loss due to reflections can be also bad.  Does Sony A7s mark I contain a self cleaning sensor mechanism which would stop working after IR-cut filter removal? 

 

It depends on what glass type you are referring to.

The composition of window glass is not well declared by manufacturers.

Good modern AR coatings for visual definitely significantly block parts of UV-A.

As far as I remember the A7S (I) have a dust cleaning function.

I have sold my A7S and cannot check the menus in the camera but you could likely find the answer by getting the users manual on the web.

 

All cameras I have seen with this cleaning-function use dichroic AR-coatings on that window for sharp blocking of UV and IR.

they are removed during conversion together with the BG glass filter to make the camera FS-converted.

Some converters can keep the piezo actuator to fool the cameras's software that it is present, but the function is lost.   

[ulf]

Yes:

https://live.staticflickr.com/5345/30020386394_4aea6a06bc_b.jpg

 

[Andy Perrin]

I am pretty sure I lost the dust cleaning function when I had it converted.

[Avalon]

Yes, A7s has dust reduction filter: https://www.lifepixel.com/tutorials/infrared-diy-tutorials/life-pixel-sony-a7s-diy-digital-infrared-conversion-tutorial

 

So it's best to remove it for good infrared and reasonable UV sensitivity  or add replacement filter? Does anyone have a video guide to the Sony  A7s conversion guide?

 

I done some research into this internal IR LED glow and learned that may not be LED related radiation leak but in fact other phenomena called Amp-glow: https://www.cloudynights.com/topic/868600-a7s-ii-amp-glow-question-experts-needed/

 

Also I read that after A7s full spectrum modification there might be issues with focus to infinity and even autofocus. Adding replacement glass seems to fix this issue but not sure what size/thickness it must be?

 

[ulf]

2 hours ago, Avalon said:

Yes, A7s has dust reduction filter: https://www.lifepixel.com/tutorials/infrared-diy-tutorials/life-pixel-sony-a7s-diy-digital-infrared-conversion-tutorial

 

So it's best to remove it for good infrared and reasonable UV sensitivity  or add replacement filter?

You must remove the dust shaker window when doing a FS conversion. It is by far the most limiting filter where UV and IR is cut away.

It is not only best, but obligatory!

 

When you remove the dust shaker and the blue-green filter you change the optical path length.

This is the same s happens if you compare how deep a glass or a swimming pool looks with and without water. ( deeper without water ).

 

Focussing a lens close means moving it away from the sensor. Bellows or extension rings for macro.

Focussing at infinity is don with the lens closer to the sensor.

 

If you remove those internal filters, the camera's sensor looks to be further away from the lens.

That is why you might have problem reaching infinity after a bad conversion.

This problem can be solved in two ways.

1. Readjust the position of the sensor moving it a distance equal to the change of optical path length. That is NOT the thickness of the removed filters!
2. Replace the filters with a suitable optical glass window (Not Window glass) where the optical path length is the same as the two filters had.

An optical window is like a filter glass, but without any filtering effect on the wavelength band of interest.

They can be made to different suitable thickness.

 

The optical path length depends on the refractive index. 

https://en.wikipedia.org/wiki/Optical_path_length

https://en.wikipedia.org/wiki/Refractive_index

 

Normally you have to realign and adjust the sensor at the end of the conversion anyhow, to get correct focus all over the sensor.

That step is omitted in the tutorials you refer to above.

How to do it is different for different camera models.

Normally there are three spring loaded screws to allow offset and tilt adjustment.

If the range of the offset adjustment is big enough you can shift the sensor forward and make a conversion without any replacement window.

 

When converting a DSLR that adjustment is critical for the autofocus as the detector for focussing is by the prism.

The distance to the sensor and focus detector must be matched. A bit more tricky.

 

I was successful when converting my Canon 60D, but realised that it was too stressful and troublesome to DIY so I handed over my Sony A7III to a professional converting company.

 

[ulf]

What troubles the guy about amp glow is rather crazy. ISO 102,400 exposure boost +6EV.

Even if it might be detectable it is not a realistic usage setting.

That boost equals an ISO setting of more than 6.4million, if I have done the math correctly.

[Andy Perrin]

Oh, you meant the AMP GLOW? I definitely have seen that, but Ulf is correct, the settings you use to make it show up are unrealistic. Also it's visible on most of the Sony line I believe (and probably most other cameras?) if you pushing things to ridiculous extremes.

[ulf]

Such things are only important for some long exposure times for Astro photography.

There are some camera projects for decreasing that by adding active Peltier cooling on the back of the sensor.

They also take several types af compensation image series beside the star image series that are used for adjusting and compensating several sensor flaws.

 

Astro is an interesting different area were modified cameras are used. Just seeing the processing can be interesting.

https://www.youtube.com/watch?v=iuMZG-SyDCU

 

[Avalon]

What size and thickness windows I need to add after removing IR/UV cut filter and dust shaker? Where to find such window?

I assume Sony A7 has same size filter as A7s.I found on Aliexpress UV fused silica window for Sony A7: https://vi.aliexpress.com/item/1005004839777770.html?gatewayAdapt=glo2vnm

Seller claims 1,5mm is best thickness for A7s.

 

[ulf]

3 hours ago, Avalon said:

I assume Sony A7 has same size filter as A7s.

No, the internal filter structure is not completely identical in A7 and A7S

They have different anti aliasing filters.

https://blog.kasson.com/the-last-word/the-sony-a7s-aa-filter/

How much that affects the filter stack thickness I do not know, but if the thickness differs the A7s is likely thicker as it's AA-filter is stronger.

 

I have checked how the Sony A series camera design set their sensor blocks to have the sensor plane correctly adjusted to have flat focus.

(With a lens at infinity all four corners should be sharp.)

The mounting screws at three positions have three adjustment washers that each can have different thickness, instead of adjustment screws I found on my Canon 60D.

See 254:

 

There are ten washer types spanning from 0.05mm to 0.5mm in steps off 0.05mm.

When you take the camera appart you must not mix them up as they must be returned to the same position.

I would colour mark them and their positions to get it right.

 

If you wanted to omit the new compensation window altogether you would have to add three identical precision washers of suitable thickness, but keep the original spacers too.

The screws are M1.7 x 5.0 so there is room for such spacers. I think they need to be around 0.5 - 0.6mm thick to compensate for the missing filters