Dynamic range and the solar eclipse

Hi,

Can anyone show a single exposure where the inner corona is not overexposed and earthshine on the Moon was recorded? The dynamic range was between 10 and 11 stops, so cameras should have been able to do it, except for one thing.

The reason I ask is the internet filled with obsessions over dynamic range. But lens flare limits dynamic range. Some veiling glare tests I see online show camera lenses with only 8 to 9 stops dynamic range. If lens flare limits dynamic range then regardless of sensor dynamic range, it would be difficult to show the earthshine clearly in a single exposure.

But one can extract earthshine images with a longer exposure to gain signal-to-noise ratio, much like we do with astrophotography and sky glow.

But the question is does anyone have a lens with low flare and a camera with a sensor with 10+ stops dynamic range and can show the corona to earthshine in one exposure?

(This excludes the pink prominences which are a stop or so brighter.)

Roger

I came reasonably close to getting it in one shot. I was using a Nikon D810 and a Nikkor 300 mm f/2.8. I have one shot at 1/60 at f/2.8, taken about 15 seconds before C3.

The first image has the exposure adjusted by -5 in LR. The inner corona is blown out over half of the Sun's perimeter.



The second image has the exposure adjusted by +5 in LR. You can see the Moon's surface, but not well. Lens flare from the prominences is clearly present.



It is vaguely possible that a 1/90 or 1/125 second exposure at mid-eclipse might have brought it all in, but I was doing 2-stop brackets due to limitations in my skills with the rented intervalometer.

Was it the camera dynamic range or lens flare that limited things? I just got my D850, which may have another stop of dynamic range. Ask me again in 2019. ;=)

--
Bob in Baltimore

This may sound like a stupid question, but why do you want earthshine?

I try to suppress it.

For the solar eclipse, I was shooting from central Oregon. I enhanced the contrast of the moon, and that had the effect of showing the solar prominences better.

rnclark said:

Hi,

Can anyone show a single exposure where the inner corona is not overexposed and earthshine on the Moon was recorded? The dynamic range was between 10 and 11 stops, so cameras should have been able to do it, except for one thing.

The reason I ask is the internet filled with obsessions over dynamic range. But lens flare limits dynamic range. Some veiling glare tests I see online show camera lenses with only 8 to 9 stops dynamic range. If lens flare limits dynamic range then regardless of sensor dynamic range, it would be difficult to show the earthshine clearly in a single exposure.

But one can extract earthshine images with a longer exposure to gain signal-to-noise ratio, much like we do with astrophotography and sky glow.

But the question is does anyone have a lens with low flare and a camera with a sensor with 10+ stops dynamic range and can show the corona to earthshine in one exposure?

(This excludes the pink prominences which are a stop or so brighter.)

Roger

Click to expand...

Roger, I think you are on the right track with this because I can show the opposite of what you want - camera w/ 10 stop DR & high flare lens. (Olympus E-M1.2 & MZ 300mm F4+MC14 = 22 optical elements) All the images that have any earthshine to dig out have badly blown highlights. Faint earthshine is @ 0.5 sec & intact highlights @ 1/30" - 4 EV apart. Have to go to probably 2 sec to show usable earthshine. That implies its really 6 EV difference so 12 EV DR would not yield detailed inner corona w/ earthshine. (These are from a friends images from a clear sky locations.)

Jerry's images using the Astro-Tech AT65Q can give you another way to look at lens scatter or lack of it in this case.

Druckmuller's site has folks using hi DR cameras w/ both scopes & tele lenses. Perhaps you can find someone from there that has determinative images on this issue..

Bobby49 said:

This may sound like a stupid question, but why do you want earthshine?

Click to expand...

It is part of the scene.

Bobby49 said:

I try to suppress it.

For the solar eclipse, I was shooting from central Oregon. I enhanced the contrast of the moon, and that had the effect of showing the solar prominences better.

Click to expand...

The prominences show just fine in my image from the eclipse, ad with earthshine:


Not sure why one would want to suppress the earthshine.

Roger

Bob in Baltimore said:

I came reasonably close to getting it in one shot. I was using a Nikon D810 and a Nikkor 300 mm f/2.8. I have one shot at 1/60 at f/2.8, taken about 15 seconds before C3.

The first image has the exposure adjusted by -5 in LR. The inner corona is blown out over half of the Sun's perimeter.



The second image has the exposure adjusted by +5 in LR. You can see the Moon's surface, but not well. Lens flare from the prominences is clearly present.



It is vaguely possible that a 1/90 or 1/125 second exposure at mid-eclipse might have brought it all in, but I was doing 2-stop brackets due to limitations in my skills with the rented intervalometer.

Was it the camera dynamic range or lens flare that limited things? I just got my D850, which may have another stop of dynamic range. Ask me again in 2019. ;=)

--
Bob in Baltimore

Click to expand...

Hi Bob,

Yes, I see the earthshine, and I agree that with a shorter exposure time it might be possible with the 810, but borderline. What ISO was this?

For inner corona, my best exposures were ISO 200 1/250 second at f/11, but it could go a little longer. http://www.clarkvision.com/gallerie...clark.c08.21.2017.IMG_0402-rl.g-c2-0.5xs.html

At iso 200, a Canon 6D has a dynamic range per pixel of 11.5 stops, a D810 a stop more, which should be enough for both cameras to get the corona to earthshine. But it is obvious lens flare is the limit, not sensor dynamic range.

Roger

rnclark said:

<snip>Hi Bob,

Yes, I see the earthshine, and I agree that with a shorter exposure time it might be possible with the 810, but borderline. What ISO was this?

For inner corona, my best exposures were ISO 200 1/250 second at f/11, but it could go a little longer. http://www.clarkvision.com/gallerie...clark.c08.21.2017.IMG_0402-rl.g-c2-0.5xs.html

At iso 200, a Canon 6D has a dynamic range per pixel of 11.5 stops, a D810 a stop more, which should be enough for both cameras to get the corona to earthshine. But it is obvious lens flare is the limit, not sensor dynamic range.

Roger

Click to expand...

<snip>

I was at ISO 64 so your best exposures are about 2/3 of a stop less than my hyped exposure that shows the Earthshine -assuming that the lens transmissions are similar.

I don't think I could pull the Earthshine up if I were one stop less than what I had - even in the middle of the disk, so I am not prepared to say that lens flare was the limiting factor. If the D850 had come out three weeks earlier, I might have evidence that says it can be captured in one shot.

I suppose that the smoke may have reduced the contrast a bit, contributing to the problem.

So, you need to convert to Nikon for the next eclipse, we both need to select our lenses for low flare, and somebody needs to stop the forests from burning!

If lens flare is believed to be the culprit, implying refractive telescopes can do better at this than camera lenses due to having fewer pieces of glass:

In theory, would a doublet potentially show less flare than a triplet / quadruplet?

rnclark said:

Hi,

Can anyone show a single exposure where the inner corona is not overexposed and earthshine on the Moon was recorded? The dynamic range was between 10 and 11 stops, so cameras should have been able to do it, except for one thing.

The reason I ask is the internet filled with obsessions over dynamic range. But lens flare limits dynamic range. Some veiling glare tests I see online show camera lenses with only 8 to 9 stops dynamic range. If lens flare limits dynamic range then regardless of sensor dynamic range, it would be difficult to show the earthshine clearly in a single exposure.

But one can extract earthshine images with a longer exposure to gain signal-to-noise ratio, much like we do with astrophotography and sky glow.

But the question is does anyone have a lens with low flare and a camera with a sensor with 10+ stops dynamic range and can show the corona to earthshine in one exposure?

(This excludes the pink prominences which are a stop or so brighter.)

Roger

Click to expand...

Roger,

This is close, but maybe no cigar.

One exposure with Nikon D500, ISO 100, 400mm f2.8 +1.4X TC, 1/60 sec, f/8.

Image calibrated in PixInsight with bias, dark, and flat frames

Saved from a linear image in PixInsight as 32bit float (strips EXIF data)

Opened in Lightroom, adjusted for corona and earthshine visibility:

Exposure setting: +7.65, contrast -100, Highlights -100, Shadows +100, Clarity +82

I can barely see light and dark areas on the moon’s surface on my monitor with the original file. Exported as full size JPEG for dpreview so not sure how it will turn out.




one exposure at 1/60 sec f/8 D500 400mm f2.8 + 1.4X TC

I suppose I could improve the quality by a round trip to Photoshop. But this is what I got with no other special tricks (like radial blur unsharp masks) just pretty much straight out of the camera adjusted in Lightroom.

I also include an average of six frames at the same exposure conditions for comparison:




Average of six exposures made at the above single exposure condition.

So, not great, but this has inspired me to use fewer frames to make a composite (fewer alignment headaches) - in fact I am getting pretty good results with just two frames one the brightest non saturated corona and one showing earthshine with reasonable SNR. BTW I was in Unity, OR and camera and lens were on an equatorial mount.

Cheers,

Bob Fugate, Albuquerque, NM