a BSI sensor riddle

Started 9 months ago | Discussions
Bernard Delley Senior Member • Posts: 1,031
a BSI sensor riddle

I would have thought that the technical challenge of back  illumination was taken for the benefits  of improved light gathering. So I would expect a higher quantum efficiency for a BSI sensor.

For  very similar pixel sizes, Bill Claffs DXO derived sensor characteristics shows

Nikon D500  (standard sensor chip)  QE = 60%

Nikon D850 (back illuminated sensor) QE = 44%

That lower QE is counterintuitive by my expectations see above. So what is wrong ?

Nikon D850
If you believe there are incorrect tags, please send us this post using our feedback form.
Rexgig0
Rexgig0 Veteran Member • Posts: 5,215
Re: a BSI sensor riddle
3

I believe the sensor is located inside the camera body, not inside the lens. (This is posted the Lens Talk section of the forum.)

-- hide signature --

I wear a badge and pistol, and make evidentiary images at night, which incorporates elements of portrait, macro, still life, landscape, architecture, and PJ. I enjoy using both Canons and Nikons.

 Rexgig0's gear list:Rexgig0's gear list
Canon EOS 7D Mark II Canon EF 135mm F2L USM Canon EF 400mm f/5.6L USM Canon EF 100mm f/2.8L Macro IS USM Nikon AF-S Micro-Nikkor 60mm f/2.8G ED +49 more
OP Bernard Delley Senior Member • Posts: 1,031
Re: English for non-native folks

Rexgig0 wrote:

I believe the sensor is located inside the camera body, not inside the lens. (This is posted the Lens Talk section of the forum.)

Thanks for helping to improve my English!

I tried to find an attractive title for my question, which I hope may be answered on this forum. The Nikon engineers certainly know a good answer, but most probably will bit tell us.

In trying to find the right equivalent for German "Rätsel"

conundrum

enigma

mystery

problem

puzzle

riddle

come to mind. The first three seemed too heavy, mysterious. I do not think it should be called a problem. Puzzle makes me think jigsaw.  And riddle may generate answers like yours, German 'Scherzfrage'.

So I definiety blundered with the Forum, till now I was convinced I hat the Photographic Science Forum.  I will repost there.

Anybody continue here only for the language discussion if interested.

This thread should be ignored for my real question. Unfortunately I cannot delete the thread.

Leonard Shepherd
Leonard Shepherd Forum Pro • Posts: 15,317
Re: a BSI sensor riddle

Bernard Delley wrote:

That lower QE is counterintuitive by my expectations see above. So what is wrong ?

Turning your comment around, if careful, consistent, controlled results contradict a theoretical result, either the theory is not sufficiently robust or the theory is overlooking an important detail.

I use both a D500 and a D850, sometimes alongside each other.

I find the reality is there is not the around 30% lower performance difference indicated using the D850, even after cropping to DX format.

-- hide signature --

Leonard Shepherd
In lots of ways good photography is much more about how equipment is used rather than the equipment being used.

 Leonard Shepherd's gear list:Leonard Shepherd's gear list
Nikon D810 Nikon D7200 Nikon AF-S DX Nikkor 18-200mm f/3.5-5.6G IF-ED VR Nikon AF-S Nikkor 16-35mm F4G ED VR Nikon AF-S Micro-Nikkor 60mm f/2.8G ED +17 more
bclaff Veteran Member • Posts: 7,143
Re: a BSI sensor riddle
1

Bernard Delley wrote:

I would have thought that the technical challenge of back illumination was taken for the benefits of improved light gathering. So I would expect a higher quantum efficiency for a BSI sensor.

For very similar pixel sizes, Bill Claffs DXO derived sensor characteristics shows

Nikon D500 (standard sensor chip) QE = 60%

Nikon D850 (back illuminated sensor) QE = 44%

That lower QE is counterintuitive by my expectations see above. So what is wrong ?

Covered in this excellent thread: https://www.dpreview.com/forums/post/60222399

And, FWIW, my values are a bit closer D500 at 57% and D850 at 49%

QE is hard to measure without a sophisticated setup (that I don't have).

-- hide signature --

Bill ( Your trusted source for independent sensor data at PhotonsToPhotos )

OP Bernard Delley Senior Member • Posts: 1,031
Re: a BSI sensor riddle

Leonard Shepherd wrote:

Bernard Delley wrote:

That lower QE is counterintuitive by my expectations see above. So what is wrong ?

Turning your comment around, if careful, consistent, controlled results contradict a theoretical result, either the theory is not sufficiently robust or the theory is overlooking an important detail.

I use both a D500 and a D850, sometimes alongside each other.

I find the reality is there is not the around 30% lower performance difference indicated using the D850, even after cropping to DX format.

The implication of the finding is that on a side by side comparison of DX cropped D850 to D500, the D500 would produce slightly better IQ because of QE, all else equal. This is not dramatic, but may be just noticeable by eye in low light images. It will not make a good image bad or a bad one good.

OP Bernard Delley Senior Member • Posts: 1,031
Re: a BSI sensor riddle

bclaff wrote:

Bernard Delley wrote:

I would have thought that the technical challenge of back illumination was taken for the benefits of improved light gathering. So I would expect a higher quantum efficiency for a BSI sensor.

For very similar pixel sizes, Bill Claffs DXO derived sensor characteristics shows

Nikon D500 (standard sensor chip) QE = 60%

Nikon D850 (back illuminated sensor) QE = 44%

That lower QE is counterintuitive by my expectations see above. So what is wrong ?

Covered in this excellent thread: https://www.dpreview.com/forums/post/60222399

I found a lot of sidetrack to colors. Your answer was to the point and among the few interesting answers.

And, FWIW, my values are a bit closer D500 at 57% and D850 at 49%

today I still find 60 and 44 % respectively on your DXO derived sensor ... page

QE is hard to measure without a sophisticated setup (that I don't have).

If you have two cameras with the same mount, and a stable light source, it is not too difficult to do a side by side comparison keeping all else the same in a controlled way.

For white light and the same exposure, I find  for example 300 electrons/ mum^2 for D500 and 230 for D850. so the relative QE are like 60% to 46%  according to my measurement. I think that is to better accuracy than 1%.

I you  care to continue this discussion, please do on the other thread which I started in the right forum.   Nikon lens talk forum happened by my mistake, totally wrong forum for this.

bclaff Veteran Member • Posts: 7,143
Re: a BSI sensor riddle

Bernard Delley wrote:

bclaff wrote:

Bernard Delley wrote:

I would have thought that the technical challenge of back illumination was taken for the benefits of improved light gathering. So I would expect a higher quantum efficiency for a BSI sensor.

For very similar pixel sizes, Bill Claffs DXO derived sensor characteristics shows

Nikon D500 (standard sensor chip) QE = 60%

Nikon D850 (back illuminated sensor) QE = 44%

That lower QE is counterintuitive by my expectations see above. So what is wrong ?

Covered in this excellent thread: https://www.dpreview.com/forums/post/60222399

I found a lot of sidetrack to colors. Your answer was to the point and among the few interesting answers.

Thank you.

And, FWIW, my values are a bit closer D500 at 57% and D850 at 49%

today I still find 60 and 44 % respectively on your DXO derived sensor ... page

You misunderstand. I don't consider the DxOMark numbers "mine"; they are simply derived from the DxOMark data.
The 57% and 49% are my own measurements; which are not currently published anywhere at the site.
The reason that my QE values aren't published yet is that some of my values are clearly pretty far off and I haven't put in a good mechanism to handle excluding individual results.

QE is hard to measure without a sophisticated setup (that I don't have).

If you have two cameras with the same mount, and a stable light source, it is not too difficult to do a side by side comparison keeping all else the same in a controlled way.

For white light and the same exposure, I find for example 300 electrons/ mum^2 for D500 and 230 for D850. so the relative QE are like 60% to 46% according to my measurement. I think that is to better accuracy than 1%.

I you care to continue this discussion, please do on the other thread which I started in the right forum. Nikon lens talk forum happened by my mistake, totally wrong forum for this.

I understand this concept. I actually handle very few of the cameras that I test.
This type of procedure is beyond the capability of almost all my collaborators so it's not part of the testing protocol.

Regards,

-- hide signature --

Bill ( Your trusted source for independent sensor data at PhotonsToPhotos )

OP Bernard Delley Senior Member • Posts: 1,031
Re: a BSI sensor riddle

bclaff wrote:

Bernard Delley wrote:

bclaff wrote:

Bernard Delley wrote:

I would have thought that the technical challenge of back illumination was taken for the benefits of improved light gathering. So I would expect a higher quantum efficiency for a BSI sensor.

For very similar pixel sizes, Bill Claffs DXO derived sensor characteristics shows

Nikon D500 (standard sensor chip) QE = 60%

Nikon D850 (back illuminated sensor) QE = 44%

That lower QE is counterintuitive by my expectations see above. So what is wrong ?

Covered in this excellent thread: https://www.dpreview.com/forums/post/60222399

I found a lot of sidetrack to colors. Your answer was to the point and among the few interesting answers.

Thank you.

And, FWIW, my values are a bit closer D500 at 57% and D850 at 49%

today I still find 60 and 44 % respectively on your DXO derived sensor ... page

You misunderstand. I don't consider the DxOMark numbers "mine"; they are simply derived from the DxOMark data.
The 57% and 49% are my own measurements; which are not currently published anywhere at the site.
The reason that my QE values aren't published yet is that some of my values are clearly pretty far off and I haven't put in a good mechanism to handle excluding individual results.

QE is hard to measure without a sophisticated setup (that I don't have).

If you have two cameras with the same mount, and a stable light source, it is not too difficult to do a side by side comparison keeping all else the same in a controlled way.

For white light and the same exposure, I find for example 300 electrons/ mum^2 for D500 and 230 for D850. so the relative QE are like 60% to 46% according to my measurement. I think that is to better accuracy than 1%.

I you care to continue this discussion, please do on the other thread which I started in the right forum. Nikon lens talk forum happened by my mistake, totally wrong forum for this.

I understand this concept. I actually handle very few of the cameras that I test.
This type of procedure is beyond the capability of almost all my collaborators so it's not part of the testing protocol.

well some of your contributors might be able to test several cameras for their relative QE with good accuracy along above lines.  That might give you a database where you can check consistency.

Keyboard shortcuts:
FForum MMy threads