SD14 is UV sensitive!

Started Apr 19, 2017 | Discussions
dbateman Contributing Member • Posts: 613
SD14 is UV sensitive!
5

Well, I finally did a quick controlled UV test of my cameras on hand an I was surprised by some of the results. First what surprised me was my light source was not as strong a UV emitting as I thought would be. So I needed long exposures. Next test I will use a UV light I have.

I used a Pentacon 6 Zeiss 80mm lens for all cameras, as it will mount to all my cameras and I fixed the aperture at f4 to try and avoid focus shift error with the normal spec to UV change. But was unsuccessful in the focus shift, as you can see the dandelions are out of focus. Dandelions are used as they have the classic bull's eye center darkness to signal bees, if you don't see the bull's eye, then your not seeing in UV.

I have a Venus Baadar II UV filter on which allows only 330nm to 390nm, with no IR.

The SD14 was about the best for UV response about 2 stops better than my Full spectrum Olympus E510. The Kodak SLR/n was also UV sensitive at ISO 160, 30 sec shutter, but noisy. Above ISO 160 the images are just too noisy. The E510 did well at ISO 1600 with shutter speeds 15 sec and 30 sec. These were comparable to the SD14 at ISO 400 and 30seconds. The Panasonic GM5 blocks all UV, nothing went through and the Nikon DF also has a fairly strong UV filter on the sensor Needing ISO over 6400 with max shutter speed 30sec. My Olympus E3 seems to had a weaker UV filter showing well at ISO 1600 and 30 second shutter.

So next test I will need to fix the white balance as this really affects the out camera image and with better initial white balance the Sigma would look better.

Below is the out of camera SD14 ISO 400, 30sec

below is the out of camera SD14 ISO 100, 30sec:

Below is the ISO100, 30sec with quick Monochrome adjustment in Sigma Pro 6.5:

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rf-design
rf-design Contributing Member • Posts: 619
Re: SD14 is UV sensitive!

Very interesting. I am a starter at UV photography but I also think that the foveons are a good base.

Technical there could three reasons why the foveons are useful at UV:

1. The ease of removing the UV/IR filter

2. Built in three layer silicon based filters.

The bayer sensors use dye filters which all three get transparent at IR. So if three is a small IR leakage in the front filter it will destroy the UV response. So there is no differentiation between UV and IR on the sensor signal. Typical lenses which a antireflection coating block nearly all UV. As a guess you need a lens with not more than 4 elements, without coating and best without glued groups. There is only a very small number of cheap non-UV lenses which come up to 50% at 350nm. This is the reason why the Baader filter with very low IR leakage is needed. Its because of transparent bayer dye filter. So in practice with foveon you could possible use a U-340, U-360 or BG25 which have IR leakage between 2% and 10% instead of Baader. At IR the foveon top layer reject further and you can make a 6-color camera by combining two exposures with two filters.

3. I suppose that the SD14 do not use a pinned photodiode for the top layer.

That increase the UV sensitivity over pinned photodiodes because you do not loose the first silicon layer direct below the gate oxide. Technical a pinned photodiode is more advanced because it isolate the surface area from the diode so effective reducing the leakage current and trap carrier mechnanism.

I found the blog form Klaus Schmitt inspiring. I was impressed by his very large flower exhibition fotos. He do not allow linking but search for

"Filter leakage in reflected UV ultraviolet photography"

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OP dbateman Contributing Member • Posts: 613
Re: SD14 is UV sensitive!

I have been dabbling in UV for a while. Yes the fewer the elements the better. Also most quartz lenses seem to be Nikon mount, which is a problem for Sigma users. After this test I will have to test my lenses. The 2 stop SD14 advantage can easily get lost with a different len. I remeber my YUS 135mm f2.8 being a good UV lens and will have to test again. The zeiss 80mm I think is a 4 element lens, whereas my YUS 135mm I think had 3 elements when I took it apart.

If your getting into UV work the baader venus 2 filter is critical. Its expensive, but worth the one time cost. Its a 48mm filter that I use with step up ring to 58mm for all lenses.

Have fun and now is the time for flower shots. I mainly posted this as I rember reading a research paper recently stating that the foveon sensor could not be used for wavelengths bellow 400nm. This is clearly wrong.

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xpatUSA
xpatUSA Forum Pro • Posts: 20,395
Re: SD14 is UV sensitive!

rf-design wrote:

Very interesting. I am a starter at UV photography but I also think that the foveons are a good base.

<>
3. I suppose that the SD14 do not use a pinned photodiode for the top layer.

Correct - that started with the Merrills.

That increase the UV sensitivity over pinned photodiodes because you do not loose the first silicon layer direct below the gate oxide. Technical a pinned photodiode is more advanced because it isolate the surface area from the diode so effective reducing the leakage current and trap carrier mechnanism.

I found the blog from Dr. Klaus Schmitt inspiring. I was impressed by his very large flower exhibition photos. He does not allow linking  . . .

Also he almost owns this forum:

http://www.openphotographyforums.com/forums/forumdisplay.php?f=113

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xpatUSA
xpatUSA Forum Pro • Posts: 20,395
Re: SD14 is UV sensitive!

dbateman wrote:

<> I mainly posted this as I rember reading a research paper recently stating that the Foveon sensor could not be used for wavelengths below 400nm. This is clearly wrong.

Clearly!

From the Foveon F13 data-sheet:

Typically, Foveon has exaggerated the QE by normalizing it to the peak value for blue. The QE scale is about 2X reality. But there is obviously some response below 400nm, so what you read was indeed hogwash.

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OP dbateman Contributing Member • Posts: 613
Re: SD14 is UV sensitive!

Your graph is interesting. It implys the IR is not as strong as I think it is. I havefound the SD14 to be an IR camera with filters added to get normal spectrum and now UV. I think my SD14 was 5 stops more sensitive to IR than my full spectrum camera, allowing for hand held 1000nm cut off shots.

About the pin sensors, does that mean the SD1M would be less sensitive to UV? That might explain where the article I read was coming from. I am glad I have the SD14 then. It was the last Sigma supportedby all software. Although nowSigma is offering DNG in camera.

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xpatUSA
xpatUSA Forum Pro • Posts: 20,395
Re: SD14 is UV sensitive!

dbateman wrote:

About the pin sensors, does that mean the SD1M would be less sensitive to UV?

That was Reiner's comment; he said:

"3. I suppose that the SD14 does not use a pinned photodiode for the top layer.

That increases the UV sensitivity over pinned photodiodes because you do not lose the first silicon layer direct below the gate oxide."

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xpatUSA
xpatUSA Forum Pro • Posts: 20,395
OOPS . . .
1

xpatUSA wrote:

rf-design wrote:

Very interesting. I am a starter at UV photography but I also think that the foveons are a good base.

<>

3. I suppose that the SD14 do not use a pinned photodiode for the top layer.

Correct - that started with the Merrills.

Sorry, it seems that the SD14 top layer diodes may be pinned. This is a cross-section of an early sensor (probably the 5um F10 predecessor to the F13), clearly showing a pinned or at least partially-pinned layer:

The above must be pre-Merrill - too many transistors for a Merrill, see below:

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danski0224 Senior Member • Posts: 1,371
Re: SD14 is UV sensitive!

There are some really interesting pictures in that forum.

I wonder what equipment is used.

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OP dbateman Contributing Member • Posts: 613
Re: SD14 is UV sensitive!

After all this talk I have been reading:

http://www.ultravioletphotography.com/content/index.php/forum/38-indexes-lists-stickies-and-references/

Seems like the domant camera used today are converted micro 43rds or Nex. Just due to the available use of lenses with focusing heliciods. I was interested in the discovery of the cheap 35mm f3.5 lenses with excellent uv character.

See:

http://photographyoftheinvisibleworld.blogspot.de/2012/07/petri-kuribayashi-35mm-vs-quartz.html?m=1

I ordered a t-mount one to test on the SD14.

Going through my old notes, when I initially ruled out the SD14 compared to my full spec E510, I was using a 10 element adaptall 90mm macro on the SD14. This compared to the 6 element olympus 35mm macro. No wonder the SD14 lost. I really should have picked up on that.

On the weekend I was able to shoot f8, 1/2 sec, at iso 100 under slight cloudy sky with the 5 element pentacon 6 80mm f2.8 lens I have. The only issue with this lens was focus shift, but I amost sorted it out. I was using the venus baader 2 uv filter.

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Scottelly
Scottelly Forum Pro • Posts: 16,508
Re: SD14 is UV sensitive!

Interesting. I wonder if this information will help me in an upcoming project. I guess I will have to experiment and see how things come out.

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Scott Barton Kennelly
http://www.bigprintphotos.com

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rf-design
rf-design Contributing Member • Posts: 619
Re: OOPS . . .
1

xpatUSA wrote:

xpatUSA wrote:

rf-design wrote:

Very interesting. I am a starter at UV photography but I also think that the foveons are a good base.

<>

3. I suppose that the SD14 do not use a pinned photodiode for the top layer.

Correct - that started with the Merrills.

Sorry, it seems that the SD14 top layer diodes may be pinned. This is a cross-section of an early sensor (probably the 5um F10 predecessor to the F13), clearly showing a pinned or at least partially-pinned layer:

Ted,

Chipworks only analysized the Merrill and Quattro sensor.

This image is the Quattro which have 9 transistors in the patent

http://www.google.com/patents/US7339216

6 Transfer NMOS built connecting the 4 pinched diode regions and the 2 buried diodes:

The pinched diode is shown here as "31":

The problem here as with many patents is that what is implemented is often not exact what is found in the illustration for the claims. Sometimes after the patent application a technical better solution is found which is still covered by the claims but differ to the description. This make it a bit fuzzy.

Here the patent illustrate 9 transistor where Chipworks count 13! I browse most patents but only found 9 and 10 for the Quattro.

Chipworks remove all images but here is a reference for the Merrill analysis:

http://image-sensors-world.blogspot.de/2012/05/chipworks-survey-of-recent-image-sensor.html

The above must be pre-Merrill - too many transistors for a Merrill, see below:

-- hide signature --

"What we've got hyah is Failyah to Communicate": 'Cool Hand Luke' 1967.

The number of identified transistor is some indication and there is one patent which refer to a pinned photodiode and have 6 NMOS:

https://google.com/patents/US8115242

The pinned diode is "16":

If the priority date is 02/07/2007 my guess is that sensors before Merrill are using a non-pinned diode which should have higher UV sensitivity.

To test this on SD's is not much difficult:

1. UV 365nm LED source

2. Check that source regarding leakage into >400nm with a spectral photometer

3. Built a hole camera with focal lenght equal to the exit pupil distance.

4. Possible use a UV transparent lens to builtin some limited imaging of UV objects

5. Remove the camera UV/IR filter

6. Measure the 365nm response from a metal reflective surface (broadband)

Reiner

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xpatUSA
xpatUSA Forum Pro • Posts: 20,395
Re: OOPS . . .

rf-design wrote:

xpatUSA wrote:

xpatUSA wrote:

rf-design wrote:

Very interesting. I am a starter at UV photography but I also think that the foveons are a good base.

<>

3. I suppose that the SD14 do not use a pinned photodiode for the top layer.

Correct - that started with the Merrills.

Sorry, it seems that the SD14 top layer diodes may be pinned. This is a cross-section of an early sensor (probably the 5um F10 predecessor to the F13), clearly showing a pinned or at least partially-pinned layer:

Ted,

Chipworks only analysized the Merrill and Quattro sensor.

This image is the Quattro which have 9 transistors in the patent

http://www.google.com/patents/US7339216

6 Transfer NMOS built connecting the 4 pinched diode regions and the 2 buried diodes:

The pinched diode is shown here as "31":

The problem here as with many patents is that what is implemented is often not exact what is found in the illustration for the claims. Sometimes after the patent application a technical better solution is found which is still covered by the claims but differ to the description. This make it a bit fuzzy.

Here the patent illustrate 9 transistor where Chipworks count 13! I browse most patents but only found 9 and 10 for the Quattro.

Chipworks remove all images but here is a reference for the Merrill analysis:

http://image-sensors-world.blogspot.de/2012/05/chipworks-survey-of-recent-image-sensor.html

The above must be pre-Merrill - too many transistors for a Merrill, see below:

The number of identified transistor is some indication and there is one patent which refer to a pinned photodiode and have 6 NMOS:

https://google.com/patents/US8115242

The pinned diode is "16":

If the priority date is 02/07/2007 my guess is that sensors before Merrill are using a non-pinned diode which should have higher UV sensitivity.

To test this on SD's is not much difficult:

1. UV 365nm LED source

2. Check that source regarding leakage into >400nm with a spectral photometer

3. Built a hole camera with focal lenght equal to the exit pupil distance.

4. Possible use a UV transparent lens to builtin some limited imaging of UV objects

5. Remove the camera UV/IR filter

6. Measure the 365nm response from a metal reflective surface (broadband)

Reiner

Thanks, Reiner, most informative.

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IbrahimMuhammed Junior Member • Posts: 36
Re: SD14 is UV sensitive!

dbateman wrote:

I have been dabbling in UV for a while. Yes the fewer the elements the better. Also most quartz lenses seem to be Nikon mount, which is a problem for Sigma users. After this test I will have to test my lenses. The 2 stop SD14 advantage can easily get lost with a different len. I remeber my YUS 135mm f2.8 being a good UV lens and will have to test again. The zeiss 80mm I think is a 4 element lens, whereas my YUS 135mm I think had 3 elements when I took it apart.

If your getting into UV work the baader venus 2 filter is critical. Its expensive, but worth the one time cost. Its a 48mm filter that I use with step up ring to 58mm for all lenses.

Have fun and now is the time for flower shots. I mainly posted this as I rember reading a research paper recently stating that the foveon sensor could not be used for wavelengths bellow 400nm. This is clearly wrong.

Try the SD14-F.

My SD14 is now easily and exclusively for my F-mount Nikon lenses.

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xpatUSA
xpatUSA Forum Pro • Posts: 20,395
Re: SD14 is UV sensitive!

IbrahimMuhammed wrote:

Try the SD14-F.

Sigma does not and has never manufactured a "SD14-F".

My SD14 is now easily and exclusively for my F-mount Nikon lenses.

Is it a custom-modified model? If so, where can the original poster buy one?

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Ted

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IbrahimMuhammed Junior Member • Posts: 36
Re: SD14 is UV sensitive!

xpatUSA wrote:

IbrahimMuhammed wrote:

Try the SD14-F.

Sigma does not and has never manufactured a "SD14-F".

My SD14 is now easily and exclusively for my F-mount Nikon lenses.

Is it a custom-modified model? If so, where can the original poster buy one?

I'm glad to see that we both agree that "Sigma does not and has never manufactured a "SD14-F"."

A gentleman named Luis Guevara - luis@sigmacumlaude.com - makes the replacement feature that allows you use Nikon's F-mount lens with the SIGMA SD14.

I purchased mine - used off someone on the Web.

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