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UltravioletPhotography

Monochrome conversion via sensor swap!


Shane

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That was very interesting.

Just today I was talking with some folks about why we couldn't have interchangeable "parts" in a DSLR - interchangeable sensors in particular. Then we could plug in an IR-tuned sensor, UV-tuned sensor, monochrome visible sensor, etc.

 

(I did get a chuckle from the article when the guy took a hammer to the sensor mounting plate to straighten it out. Do-It-Yourself does have the occasional risk.)

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In addition to Maxmax there is another person offering Monochrome conversion by removing the Bayer array and microlenses.

 

http://hyperdslr-mods.blogspot.com/

 

I have been following his progress on the CloudyNights forum for the last year or so. He now offers a warranty as well as "reasonable" prices. I am in communication with him regards to some of his methodology with respect to potential latent conversion issues. He can provide this service for full frame Nikon and Canon in addition to many other models.

 

The potential for UV is huge with respect to sensitivity as well as resolution. For IR there is likely little sensitivity gain but resolution gains are still there.

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Very interesting. It would appear that HyperCam works with Baader filters? I wonder if they are able to resize a Baader-U for use as an internal filter in a modded camera?

 

But, Shane, please let this HyperCam fellow know about the internal IR shutter monitor which contaminates UV/IR photos in the modified Nikon D700/D3/D3S/D3S/D4/D4S bodies. I see that he has listed some of them in his price list. Not good if it is not clarified that use of such cams with external filters can result in contaminated photos.

Internal UV-Pass is probably ok for the given cams if filter has very low IR leak. Internal IR-Pass can still get contaminated although it is probably not as damaging as in the UV case.

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In addition to Maxmax there is another person offering Monochrome conversion by removing the Bayer array and microlenses.

 

http://hyperdslr-mods.blogspot.com/

 

I have been following his progress on the CloudyNights forum for the last year or so. He now offers a warranty as well as "reasonable" prices. I am in communication with him regards to some of his methodology with respect to potential latent conversion issues. He can provide this service for full frame Nikon and Canon in addition to many other models.

 

The potential for UV is huge with respect to sensitivity as well as resolution. For IR there is likely little sensitivity gain but resolution gains are still there.

 

 

I have been interested in the same thing and been following the CloudyNights different forum discussions, but have not seen the HyperCam blog before. Thanks Shane for sharing.

 

How much increase in UV sensitivity would you expect from such de-bayered camera, Shane?

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I think I would miss the false colour a bit.

But mono-UV would be a very useful camera for detail.

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The Bayer/microlens layer is shown in some reverse engineering cross-sections to be around 7 to 8 ~5um thick. Assuming it is similar for the Nikons then this amounts to a large UV absorption barrier. I can only imagine removing it should provide a substantial sensitivity gain at the UV end with little improvement at the IR end (the layers are transparent to IR so removing them gains nothing in light sensitivity, only resolution).

 

The findings of Dan at Maxmax seem to support this as he reports a 6 fold increase in light sensitivity at the UV end dropping to zero increase at the 715nm IR end.

 

There may be a catch 22 situation with regard to the stripping process.

 

Mechanical removal of the layers appears to result in a "tide mark" of residual Bayer/microlens material at the sensor borders because it is too risky to get that close to the bond wires with mechanical methods.

 

Chemical stripping has the potential to completely remove the layers without surface damage and leave no "tide mark" at the sensor periphery. At first glance this appears the optimum approach.

 

The downside of mechanical stripping is the likelyhood of residual surface damage, scratches etc but possibly there may be one significant benefit of the residual "tide mark".

 

At the sensor periphery lie the (reference) Optical Black sensels and uncovering these must have some consequences possibly creating the potential for shadow banding. Although there is no hard before and after testing data that I am aware of, a cursory review of general comments left by those "playing" with these monochrome conversions seems to indicate a consensus that those sensors modified by mechanical means do not appear to exhibit banding issues whereas those chemically stripped possibly show a trend of banding under some conditions.

 

It actually seems ironic that UV photographers who really could do with a boost in sensitivity (possibly 600%) have not experimented in this direction whereas the astrophotographers, who only really benefit from the resolution gains (perhaps only around 30%), are all over this.

 

We certainly don't seem to lack the daring.

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I am well aware of Dan's statements, however, I have not seen any tests that would confirm it. But I have not looked hard enough.

 

On the other hand, I would like you to read this statement (posted on the digilloyd blog here http://diglloyd.com/blog/2013/20131128_1-NikonD800-monochrome.html and attributed to Dan):

 

"I have one customer who has told me he uses my monochrome camera down to 240nm with UV lasers they make."

 

Would you agree that this is possible with de-bayered camera?

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I have read that too, I am not quite sure how they are implementing the DSLR in that process - photographing the actual laser light? Remember 240nm LASER is a lot of light. UV excitation may also be occurring in this "process"?

 

If Andrea can capture 290nm (albeit impractical due to exposure time), would a 6 fold increase in sensitivity AND mega-power laser light help despite all other sensor level anti-UV factors working against it? Possibly. Assuming a UV friendly coverglass (or none at all), the main barrier is reflection and junction depth. If you create enough electron hole pairs, even though they may be at the surface, the likelyhood of some of them reaching the junction is improved.

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Thank you again for the explanation. It is difficult to interpret these statements without having any additional information.
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From an inquisitive standpoint, I would love to see the hard core spectroscopy and exposure data for before and after scenarios with these different conversions. Even more so when the conversion cost is $6K. At that point you are approaching the price of a Leica Monochrom which displays a RAW data histogram (as opposed to the typical jpg histogram), has the built in algorithms to know that it is a monochrome sensor and treats the data accordingly.

 

How easy is it to remove the IR block filter from the Leica Monochrom? :D

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Gotta be easier than removing microlenses and bayer arrays from DSLR sensors. :D
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Scratching off microlenses and bayer arrays is easy. Not damaging the rest of the sensor is a difficult part. Believe me, I tried :D
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OK, I've got a D300 sitting here unused. How exactly does one mechanically remove microlenses and bayer arrays?
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The biggest problem is actually removing the coverglass without breaking it which can damage the sensor surface or bond wires.

 

Nikon cover glasses are typically epoxied on requiring heat, hydrocarbon solvent (dangerous combination let alone the health hazard from vapours) and mechanical prying.

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OK, I've got a D300 sitting here unused. How exactly does one mechanically remove microlenses and bayer arrays?

 

Give that women a medal! :D

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I haven't seen a tutorial yet that addresses the problem of using adhesives. In the semiconductor industry the use of adhesives can have severe consequences if appropriate care is not taken. The primary concern is outgassing during curing. Any volatiles will deposit on the underside of the coverglass or on the sensor surface. How detrimental this may be depends on the quantity of volatiles and the chemical outgassed. Most silicone adhesives can outgas corrosive chlorine gas, especially detrimental to exposed circuitry such as bond pads (where the gold wires attach).

 

As to putting epoxy on the bond wires, that made me cringe. I have worked around exposed bond wires and it is tricky (no repairing unless you have a die wire bonder). I would rather chance the exposed wires than apply epoxy to them.

 

I believe the mechanical method is required for Canons due to a hard interface layer that prevents direct actions of solvents. This differs from Nikon which appear not to have that layer.

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But isn't the internal software in the camera going to be at odds with the new unbayered data?

Maybe not if shooting raw, I suppose. But other data massage happens too.

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At that point you are approaching the price of a Leica Monochrom which displays a RAW data histogram (as opposed to the typical jpg histogram), has the built in algorithms to know that it is a monochrome sensor and treats the data accordingly.

 

If you are shooting RAW I think there are only some minor issues on a mono conversion, until you try to enter your raw converter. Then the converter needs to understand this is a mono sensor and not demosaic/interpolate the data and for this there are some options e.g. dcraw and more advanced choices.

 

Some minor in-camera issues might include (jpg) histogram, (jpg) highlight indicators, WB application (use UniWB), hot pixel suppression (map) which relies somewhat on the blurring during interpolation, perhaps some firmware level low level noise correction etc.

 

Dan has some NEF files from his D800 mono conversion available for download if you want to play.

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