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UltravioletPhotography

Snag with Sony A7R in UV


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Vivek Iyer just sent me this infomation posted to his Flickr account, https://www.flickr.c...otos/vivek-iyer, which indicates why these Sony models have so much trouble in UV.

Yep, that's similar to what I've seen with the ones I've had converted. This is why I've asked for the sensor cover glass to be removed and replaced with UV fused silica for the last two I had done. Although I must admit, those A7R ones are about as extreme as I've seen in terms of blocking UV.

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Vivek Iyer just sent me this infomation posted to his Flickr account, https://www.flickr.c...otos/vivek-iyer, which indicates why these Sony models have so much trouble in UV.

 

That's a great graph, Birna. Exactly explains my experience with the A7R.

 

But look at the A7 - that looks incredible - 60% sensitivity at 250nm! Can that be true? I could have got one instead of ther A7R for 2/3 of the price, but I think it was only 24 Mpixels and so didn't see any point as I have that on the A6000. But I might think again about that.

 

But can that graph really be true?

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Vivek Iyer just sent me this infomation posted to his Flickr account, https://www.flickr.c...otos/vivek-iyer, which indicates why these Sony models have so much trouble in UV.

That is very strong words and is only valid for Bernard’s problem is with narrowband UV pass filters particularly those at/under under 340 nm.

 

The graphs are not for camera sensitivity, but likely for transmission of different camera sensor's cover glass.

 

It would be interesting to see / measure transmission of cover glasses from other modern cameras, like Nikon Z5 and Z6.fI wonder if it would be possible to get a sample removed during conversion?

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Sorry if there is any confusion -- yes, the graphs deal with the cover glass.

 

Vivek is very trustworthy and the data obviously comply with member experiences.

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The A7 III doesn't look that bad there - 10% at 320nm. That's comparable to the El Nikkor 80 or 105, from what I remember.

 

But it's the the A7 that interests me - does anyone have any input to support the graph from Vivek Iyer?

The graphs looks quite reasonable and I think they can be trusted. Measuring a flat optical part like a window or filter is much easier to do than measuring a lens.

 

One advantage with the more modern BSI sensors is the greater dynamic range with less noise in the shadows.

That helps WB lifting the signals attenuated in the shorter wavelengths, if the image is from a wider band filter like Baader U or a typical filter stack.

 

I chose the A7 III due to it's dual gain BSI sensor and am very happy with the performance.

https://www.dpreview.com/reviews/sony-a7-iii-review/6

You can dial in the A6000 in the exposure latitude test

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The graphs looks quite reasonable and I think they can be trusted. Measuring a flat optical part like a window or filter is much easier to do than measuring a lens.

https://www.dpreview...a7-iii-review/6

You can dial in the A6000 in the exposure latitude test

 

(ultraviolet.com seems to be playing up this morning. I've been having lots of problems - this is my third attempt at this post ...)

 

Thanks, Ulf. But if the graph is for the cover plate only, it doesn't tell us much about the sensor assembly as a whole - except that the cover plate is not a limiting factor like it is on the A7R etc. So the A7 may not be any better in UV reach than the A6000.

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(ultraviolet.com seems to be playing up this morning. I've been having lots of problems - this is my third attempt at this post ...)

 

Thanks, Ulf. But if the graph is for the cover plate only, it doesn't tell us much about the sensor assembly as a whole - except that the cover plate is not a limiting factor like it is on the A7R etc. So the A7 may not be any better in UV reach than the A6000.

Except that it is a full frame camera. It might be worse than the A6000 if the sensor is less favourable.

If I were into deeper UV an A6000 might have been an interesting complement to my A7III.

Even better wold have been some camera with BSI-sensor that were monochrome converted,

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Editor's Note:

Bernard: Ultraviolet.com seems to be playing up this morning.

I've been having lots of problems - this is my third attempt at this post.

Editor: No reports on the server side. So it must be your local ISP?

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I'm sitting here trying to think what to do about camera recommendations in the Sticky. In light of Vivek's sensor glass cover measurements, I think that I should put something into the Sticky about conversions of the various Sony A models. A7 good, the rest not so much.

 

But of course we don't know anything about Canon/Nikon/Panasonic/Olympus sensor glass covers either.

 

We never have enough information in order to recommend the "best" cameras for reflected UV photography, do we?

 

Interestingly, Birna and I have been photographing in reflected UV for years without thinking too much about "reach". And I never felt I was having any particular "trouble" back when I used my converted Sony A7R in reflected UV except for its un-ergonomic handling and lossy compression both of which I disliked.

 

Now, these days shooting below 350 nm seems to be something which everyone wants to do.

 

Sticky Update:

  • Should include remarks about sensor cover glass
  • anything else I should try to add??

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I'm sitting here trying to think what to do about camera recommendations in the Sticky. In light of Vivek's sensor glass cover measurements, I think that I should put something into the Sticky about conversions of the various Sony A models. A7 good, the rest not so much.

 

Sticky Update:

  • Should include remarks about sensor cover glass
  • anything else I should try to add??

 

I think making recommendations is very tricky. People will have their own favourites that they have had good experiences with but will not know all the other gear out there and so cannot make informed judgements. So there would have to be clear criteria that everyone could use to form a recommendation. It would also have to be clear what the recommendation is for because different things will be important to different people - image quality, focus shift, contrast, depth of colour, UV reach, ...

 

I think it's better to present facts in a coherent format so that users can judge what kit is right for their application.

 

There's no harm including comments on cover glass transmission where we have them, but I wouldn't put too much emphasis on this. As you say, the info. is available for only a few sensors. What is more important to know is the UV sensitivity of the whole sensor subsystem - good cover glass transmission is useless if some other aspect of the sensor (Bayer filter, AR coating, or whatever) harms its UV sensitivity. For example, the high transmision of the A7 cover glass doesn't tell us that the A7 is going to be a good UV camera. But I guess negative comments, like for the A7R et al., are useful because it makes it clear that those cameras cannot provide stellar performance at shorter wavelengths.

 

What I would really appreciate is sensor subsystem sensitivity charts, equivalent to Ulf's Herculean efforts on lens transmission. But don't ask me how we can get them!

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I'm sitting here trying to think what to do about camera recommendations in the Sticky. In light of Vivek's sensor glass cover measurements, I think that I should put something into the Sticky about conversions of the various Sony A models. A7 good, the rest not so much.

 

But of course we don't know anything about Canon/Nikon/Panasonic/Olympus sensor glass covers either.

 

We never have enough information in order to recommend the "best" cameras for reflected UV photography, do we?

 

Interestingly, Birna and I have been photographing in reflected UV for years without thinking too much about "reach". And I never felt I was having any particular "trouble" back when I used my converted Sony A7R in reflected UV except for its un-ergonomic handling and lossy compression both of which I disliked.

 

Now, these days shooting below 350 nm seems to be something which everyone wants to do.

 

Sticky Update:

  • Should include remarks about sensor cover glass
  • anything else I should try to add??

 

Sigma Foveon & Bayer

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I'm sitting here trying to think what to do about camera recommendations in the Sticky. In light of Vivek's sensor glass cover measurements, I think that I should put something into the Sticky about conversions of the various Sony A models. A7 good, the rest not so much.

 

But of course we don't know anything about Canon/Nikon/Panasonic/Olympus sensor glass covers either.

 

We never have enough information in order to recommend the "best" cameras for reflected UV photography, do we?

 

Interestingly, Birna and I have been photographing in reflected UV for years without thinking too much about "reach". And I never felt I was having any particular "trouble" back when I used my converted Sony A7R in reflected UV except for its un-ergonomic handling and lossy compression both of which I disliked.

 

Now, these days shooting below 350 nm seems to be something which everyone wants to do.

 

Sticky Update:

  • Should include remarks about sensor cover glass
  • anything else I should try to add??

 

Obviously the Olympus cameras are best.

But than why do I keep wanting a Z5 or Z7. Never happy.

 

Andrea I can say without a doubt that the Em1mk1 and Em5mk2 both have deep uv transmission coverglass. My Kolari converted Em5mk2 can see UVC, which shocked me. Added with high resolution shot mode and in camera focus stacking with the hack for EF mount lenses with a Metabones adapters, its quite a fun camera. Also if you only want UVA, you don't need to convert the Em1mk1 or Em5mk2. The conversion only gave me a stop more UV using the common Baader venus u filter in sunlight. A Straight edge u filter, you wouldn't see the difference.

 

The ultra wide Sigma 10-20mm f4/5.6 lens works nicely on the Olympus in EF mount, disadvantage is the 77mm filter thread. But can be used also with a speed booster. I still need to compare the Metabones vs Viltrox boosters for UV transmission. But the Viltrox booster will not Af fast enough for in camera focus stacking.

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I think that I should put something into the Sticky about conversions of the various Sony A models. A7 good, the rest not so much.

 

But of course we don't know anything about Canon/Nikon/Panasonic/Olympus sensor glass covers either.

 

Interestingly, Birna and I have been photographing in reflected UV for years without thinking too much about "reach". And I never felt I was having any particular "trouble" back when I used my converted Sony A7R in reflected UV except for its un-ergonomic handling and lossy compression both of which I disliked.

 

Now, these days shooting below 350 nm seems to be something which everyone wants to do.

 

Sticky Update:

  • Should include remarks about sensor cover glass
  • anything else I should try to add??

 

"various Sony A models. A7 good, the rest not so much." I strongly disagree about that statement as I think very may members do not look for deeper UV-photography.

Even if there are many interesting posts by Bernhard, David and Stefano in that direction on the forum that do not mean the full user base is reflected there.

 

Just as for lenses the UV reach has to be good enough, not more.

Then other parameters are more important.

As there always has to be compromises, hunting for a camera with very deep UV reach, could harm the final result if you are not doing that type of photography.

 

The urge for trying to shoot below 350nm is likely partly due to the lack of understanding how difficult it is and what is needed beside a lens and camera with deep UV-reach.

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Editor's Note:

Bernard: Ultraviolet.com seems to be playing up this morning.

I've been having lots of problems - this is my third attempt at this post.

Editor: No reports on the server side. So it must be your local ISP?

 

No, I'm (still) having problems just with this site - getting intermittent long delays and timeouts. All other sites are working fine for me.

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No, I'm (still) having problems just with this site - getting intermittent long delays and timeouts. All other sites are working fine for me.

 

Same here. Time outs and errors with my recent post even.

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Andy Perrin
My A7S has always seemed fine. I know it works in the 340s, so reach is acceptable to me. If I wanted to go further than I would get a debayered camera.
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