Low Light Photography

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Jason C Wells
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Low Light Photography

Post by Jason C Wells » Mon Jun 15, 2015 4:08 pm

Would someone please recommend an inexpensive camera (or website with good searching) that has good low light performance and remote manual shutter control? I know nothing about cameras except for what is in my phone. I don't need fancy lenses or high resolution. I just need to capture faint glowing things.

Thanks,
Jason C. Wells

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Richard Hull
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Re: Low Light Photography

Post by Richard Hull » Mon Jun 15, 2015 6:49 pm

You are asking for a lot and a little. Not necessarily high res, but a remote shutter control....Hmmm. Typically the lower priced digital cameras have no remote shutter trigger control. The more expensive ones do.

It is a far better idea to get a good video camera and obtain 60 fields/30 frames recorded per second and play the digital video back on a piece of software to capture desired single frames and save them as JPEGs. SNIP is a good piece of freeware to capture video frames.

We have discussed this a bit in past postings here.

Richard Hull
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Nick Peskosky
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Re: Low Light Photography

Post by Nick Peskosky » Mon Jun 15, 2015 10:31 pm

Jason,

If you're looking for an all around superb camera with remote control (WiFi), I'd look no further than one of the GoPro Hero 3/3+'s. They run about 150-300$ and can capture 1080p video as well as 12Mp resolution photographs. I'm not sure how the low-light performance is on mine but if you want I'll take some pictures of plasma in my Fusor with the one I own for skiing/kayaking and you can make your own judgments. The newest models have a downloadable Android/iPhone app which allows you to remotely view and control the camera feed on any compatible cellular device. Also, it would be easy to find an inexpensive mount for the camera now that the GoPro brand is almost ubiquitous across most retailers, whether big-box or online based.
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Carl Willis
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Re: Low Light Photography

Post by Carl Willis » Mon Jun 15, 2015 11:28 pm

I take low-light photos of radiation-related subjects frequently. I picked out a Fujifilm X-E2 mirrorless camera with that application specifically in mind, and it meets expectations. Obviously, you can spend a lot more money on a better camera and ass-kicking lenses. In particular, this is the domain of cryogenically-cooled astrophotography cameras that can cost tens of thousands of dollars. But I presume we are talking about consumer-grade cams and techniques.
DSCF0180_v2.jpg
This image shows the glow caused by beta particles from a ~20-microcurie radium source striking a phosphor screen that has a magnet under it. This is two 20-minute "light" frames added and two 20-minute dark frames subtracted, taken with a Fujifilm X-E2 mirrorless camera at ISO 3200 and that camera's kit zoom lens at 18mm(eq) and f/2.8. The camera, minus battery, was put in the refrigerator for a few hours prior to taking the shots.
Am_radiograph_composite.jpg
This image shows the glow caused on a fluoroscope screen by 59-keV gamma rays from a 6-millicurie Am-241 source. The radiation casts a shadow of the "artistically"-arranged lead metal in the black box. This is two 50-minute "light" frames added and two 50-minute dark frames subtracted, taken with the same camera and lens mentioned above. ISO 4500 and the same lens configuration. I should point out that the glow in this scene is below the limit of my eyes to discern.
bad2thabone.jpg
This image shows an x-ray fluorographic greeting card I sent to my cousin Jeremy. Behind the door next to me is an x-ray tube, in my left hand is a piece of card stock with wording formed by gluing lead solder wire to the card, and in my right hand is a fluoroscope screen upon which the shadow of the lead letters is projected. 50mm-eq f/1.4 prime lens wide open on the X-E2 camera at ISO3200, 1/8 second. Spare me the sanctimony, I already know this is a failure to lead by good example.

Here's what matters on the equipment and technique for low-light photos.

-Geometry: Probably the most important concept is getting the sensor close to the subject, right at the limit of the lens focus. Beyond that, you want to use large prime (non-zoom) lenses with large apertures for the best light collection capability. The geometry and the lens are more important than anything else in this list. Small f/numbers severely limit the depth of field on close subjects, so your aperture choice will likely be dictated by the physical extent of the subject. Unfortunately, big lenses with big apertures cost big money. But the idea that you want to pick the lowest f/number that will still put the subject reasonably in focus remains important on any lens.

-Choice of camera design: SLR cameras often have the biggest and best sensors, but they put the bulky reflex mirror between the sensor and the lens. Mirrorless designs do not have this to deal with and the sensor can be very close to the lens. This distance dictates physically larger and more expensive lenses to produce the same light intensity on the sensor in SLR designs. I suggest a mirrorless camera with a big sensor is the better choice for low-light in general, and where the specific advantages of the SLR configuration (rapid focusing, chiefly) are not so important. A number of mirrorless system cameras have become popular in the budget range of $500-$800.

-Choice of light sensor: Faster light gathering and lower noise comes from larger CCD / CMOS chips with no color filter, and fewer (larger) rather than more (smaller) pixels. I have yet to see a digital camera on the consumer market that offers a "bare", filterless sensor, so your next best bet is probably lower-end astrophotography cameras running a couple thousand dollars. Some security cameras have CCDs generally meeting the specs except for size, and a few models allow for long integration time. The downside is that they generally produce an analog signal that must be digitized again in a vid capture device at some expense to image quality. Adapting security cameras to good lenses also typically takes some effort in the making of custom mounting parts.

-Light collection time: Longer is better, obviously. Because of the contribution of readout noise, it is now generally preferable to make one exposure for X minutes rather than stack X exposures at 1 minute each.

-Sensor temperature: This has a rather large impact on the noise performance of consumer digital cameras with silicon sensors. I see a huge difference in a one-hour dark frame with my Fujifilm X-E2 at room temperature versus 5 deg. C. right out of the refrigerator. So you should cool the camera or preferably the entire working space to the extent that is reasonable. One does run the risk of causing condensation in the lens or the camera electronics, so be very careful. Consumer cameras are not cryogenically safe, but even a little bit of refrigeration makes a noticeable difference in noise.

Sensor digitizer bit depth: You want to saturate the bit depth of the camera and preserve value resolution particularly at the dark end. In low-light scenarios this means setting the highest "native" ISO of the camera and shooting RAW rather than jpeg.

-Make sure your camera has a "bulb" mode and the ability for external shutter release, preferably electronic. That way, you can time the shutter for as long as you want from a remote location using simple hardware. Make sure the camera allows you to turn off its display and electronic viewfinder. Dealing with light from the camera itself getting into your shot is really annoying. Every camera I have owned has had some kind of light source needing fixing.

-Dark frames: These are helpful at subtracting hot pixels and certain other types of noise. They can be used to help "flatten" the field owing to sensitivity variations in the pixels of the sensor. Some cameras can be programmed to take them automatically by operating the sensor without opening the shutter.
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Jason C Wells
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Re: Low Light Photography

Post by Jason C Wells » Mon Sep 14, 2015 1:39 am

Excellent posts guys. Thanks!

Later,
Jason

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Re: Low Light Photography

Post by Jerry Biehler » Mon Sep 14, 2015 7:21 am

If you want real low light capable cameras look at the ones used for astrophotography. Meade sells some cheap-ish cameras that have cooled sensors to keep the noise down for long exposures.

You can also look at older Photometrics cameras on ebay. I got one off ebay, a Photometrics Quantix camera with a 6.3MP monochrome sensor. The sensor is sealed in a vacuum chamber with a quartz window and is cooled to -35c. Pretty neat camera.

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Rich Feldman
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Re: Low Light Photography

Post by Rich Feldman » Sat Oct 22, 2016 10:01 pm

This is a good thread for posting some new, quantitative data. Also to share a recent double success in my amateur science hobby.

1. Quick and dirty spinthariscope.

Before this month I had never actually seen any spinthariscope. Then some translucent plastic sheets with ZnS(Ag) fluorescent coating arrived from one of those nice guys named George. I got out a smoke detector circuit board. Removed the outer electrode from ionization chamber assembly, exposing the alpha particle source. Less than 1 microcurie of americium-241. I placed one of the films on top of the source, turned off all the lights, and made a phone call.

After about 5 minutes, as my eyes became dark-adapted, a dim fuzzy glow became visible. It stayed put when the film was moved from side to side. On close examination with a small convex lens, the spot was all sparkly! 8-) Imagine how Prof. Crookes felt, as the first human to see the phenomenon.

2. Taking a picture of the microcurie glow.

It'd been a few years since I did any time-exposure photography. In the meantime, I'd bought an out-of-date, used DSLR on craigslist, to get some hands-on experience. A Canon EOS Rebel XT (a.k.a. 350D). The attractive detail was its 50mm f/1.8 FD lens. As with most of my hobby purchases, it sat around unused for a couple years.

Cutting to the chase, here is one picture taken with lights on:
9835r.PNG
and one with lights off, except for a flashlight directed away from the subject for a few seconds:
9834r.PNG
Those are screen capture snips from original jpg's -- no image manipulation. Before seeing the photo, I thought the glow color was pale green. I guess it was simply "bright" enough for scotopic vision to see that something was there.

Now that I'm reacquainted with Exposure Value (EV) numbers, they seem to be a useful metric for cameras in this kind of service. They indicate by how many powers of two the camera settings attenuate (or boost) the effective exposure. EV Zero is a 1-second exposure at f/1 with ISO 100 sensitivity. Bright sunlit scenes call for EV of about +16, for example 1/500 second at f/11. Negative EV's are needed for very dim stuff.

My trusty old Coolpix 950 can only go to 8 s shutter time, f/2.6, and ISO 320. That translates to minimum EV of -2 (more precisely, -1.92). Using that on the spinthariscope gave only black frames, noise, and a few hot pixels.

The early digital EOS goes to 30 s, f/1.8, and ISO 1600, for EV of -7. I think it took an acceptable picture of the spinthariscope.

My neighbor's Pentax K20D can also reach -7 EV, with a different mix. Same 30 second shutter. Its "kit" zoom lens is only f/3.5, but sensor sensitivity can be set up to nominal ISO 6400. Its picture of the same spinthariscope was much less definitive:
3761r.PNG
I want to repeat the exercise another day. At this point it supports the advice from Carl Willis (above) to respect fast glass more than big ISO numbers.

Don't forget to consider cameras that can run on an AC adapter. Time exposures typically draw battery power for as long as the shutter is open. Something I learned with a film camera, the last time Halley's Comet was around. That was the second Halley's appearance since the last time the Chicago Cubs won a World Series. :-)
Last edited by Rich Feldman on Sat Oct 22, 2016 11:42 pm, edited 7 times in total.
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Richard Hull
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Re: Low Light Photography

Post by Richard Hull » Sat Oct 22, 2016 10:15 pm

I have made a number of spinthariscopes over my many years. I will be rather stunned if you can capture the individual flashes without an astro-cooled system. I do think a 2nd or 3rd gen image intensifier, (night scope with modified lensing), would pick them up for videoing, albeit in green flashes instead of the optically perceived white flashes. Diffuse glows are easy to catch. A video of the flashes would be fabulous.

The dark adapted human eye and a well made spinthariscope remains the best way to view and be amazed at individual nuclear events occuring in real time.

Richard Hull
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Re: Low Light Photography

Post by Grigory_Heaton » Sat Oct 22, 2016 10:26 pm

That's an incredible picture! I actually just received a similar ZnS(ag) sheet a few weeks ago and tried this out myself. I was able to see the glow, but only having access to some mediocre cell phone cameras I couldn't get a picture. Awesome job with that! I will definitely have to try looking at it under a lens.

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Richard Hull
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Re: Low Light Photography

Post by Richard Hull » Sat Oct 22, 2016 10:40 pm

The fireworks is best viewed with the eye from a rather weak alpha source or if a strong one, by placing it near the alpha range limit from the screen.

The real thrill is to see the pitch black of what appears a vast ink black void using a super wide field lens like an erfle or special wide field kellner telescope eyepiece with about 20 stars exploding in the black void each second.

A lot of roaring undulations in a glowing mass is not a spinthariscope image that amazes. One can observe this on the hands and numerals of an old radium dial with a simple magnifier.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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