Digital time exposures.

Grandpa Ron

Been spending a lot of time on here!
Joined
Aug 9, 2018
Messages
1,144
Reaction score
692
Can others edit my Photos
Photos OK to edit
I was experimenting with available light photography. I was quite please with how much a DSLR can capture with a high ISO, bright moon and a 30 second shuttered. I was also capturing some darker sky constellation photos and thought about some star trails. My Canon t6 Rebel has a max timer setting of 30 seconds, but I need a 3 hours exposure window.

So the question is, "If I use the Bulb setting on the camera, will I over heat the sensor or hurt the battery with 3 hours Bulb exposure?)
 
Interesting question, and I don't know about long long exposures and the sensor or heating up.

With film it's different, you can make very long exposures but then you deal with reciprocity and the film losing sensitivity.

But You might consider 3 hours of 30 second exposures and combine them.

What's your reason for a 3 hour exposure? What are you trying to capture?
 
My goal was to capture star trails. Besides my Canon digital I do lot of tinkering with a 1909, 4x5 view camera my late uncle gave me. While the high ISO of the digital camera will capture constellations, with an f4.5 lens and 400 ISO film the old view camera does not do a very good job on individual stars.

So I pointed it in the general direction of the North Star. This time of year it gets dark from about 10:00 pm 5:00 am so I chose to expose from 11:00 pm to 2:00 am or 3 hours at f8. 3 hours is 45 degrees of the earth rotation, that is a pretty good chuck of the sky.

As you can see, the sky glow is a problem, but adding sepia made a slight improvement in the contrast. I have seen better star trail photos but this was not bad for my first try.

I would like to use my digital camera, but taking a picture every minute or so for 3 hours seems like a lot of work. :)

Arista EDU 400 ISO, F4.5, 3 hours.
Star trails 3 enhanced.jpg
 
I was experimenting with available light photography. I was quite please with how much a DSLR can capture with a high ISO, bright moon and a 30 second shuttered. I was also capturing some darker sky constellation photos and thought about some star trails. My Canon t6 Rebel has a max timer setting of 30 seconds, but I need a 3 hours exposure window.

So the question is, "If I use the Bulb setting on the camera, will I over heat the sensor or hurt the battery with 3 hours Bulb exposure?)
I don't know where from, but a few years ago I read where some company was installing some sort of cooler on select camera models for astrophotography. Seems it was about $400 US. I suggest you ask Canon about your camera. Good luck!
 
OK you asked about time exposures, long with digital. The answer is, take many images and then use Startrails to blend them. Rather than a terribly long exposure. http://startrails.de/

Yes, if film, you are correct, one really long exposure.

Yeah, the accumulation of light and finding dark skies, is a real problem.

I realize this is about x-rays, but the same applies to photos of light.

"
The reciprocity law constitutes one of the fundamental rules of photography and of radiography. It states that the quality of a series of photographic or radiographic films will be uniformly constant if the exposure times with which the films are made vary reciprocally with the intensities of the exposing radiation. Thus, the law implies that when other things are equal a roentgenogram exposed for 1.0 second and with a tube-current of 100 milliamperes will be identical to one exposed for 10 seconds and with a tube-current of 10 milliamperes.2
The reciprocity law is based on the assumption that the density or blackening of a photographic film is dependent merely on the exposure or quantity of radiant energy which the film absorbs and is independent of the rate at which the energy is applied (i.e., is independent of the intensity of the exposing radiation)."

Here's the article about film on Wikipedia, which quotes all kinds of physics and formulas and things, but boiled down to what we would need to know,

"
Reciprocity failure is an important effect in the field of film-based astrophotography. Deep-sky objects such as galaxies and nebulae are often so faint that they are not visible to the un-aided eye. To make matters worse, many objects' spectra do not line up with the film emulsion's sensitivity curves. Many of these targets are small and require long focal lengths, which can push the focal ratio far above f/5. Combined, these parameters make these targets extremely difficult to capture with film; exposures from 30 minutes to well over an hour are typical. As a typical example, capturing an image of the Andromeda Galaxy at f/4 will take about 30 minutes; to get the same density at f/8 would require an exposure of about 200 minutes.

When a telescope is tracking an object, every minute is difficult; therefore, reciprocity failure is one of the biggest motivations for astronomers to switch to digital imaging. Electronic image sensors have their own limitation at long exposure time and low illuminance levels, not usually referred to as reciprocity failure, namely noise from dark current, but this effect can be controlled by cooling the sensor."

Good Luck and happy star shooting.

North Star, always a favorite reference point.

20211214-826-1001-geminids-web.jpg


My biggest obstacle seems to be, getting a nice clear sky. Then there's dew and airplanes, and satellites and light pollution. The last is what shows in your film exposure, as it adds up and ruins the image.

Stars are very bright, meteorites are not. I remember years ago, taking all kinds of 10 second exposures, during Perseids and wondering why all I got where stars. Oh there are probably meteorites in there, but the exposure, didn't capture them. That's why I moved up to 3200 or H (on the older cameras) and faster lenses, and 30 second exposures.

Hey thanks for asking, I wonder where those old photo are from those nights in 2010-11 or 12? I didn't know about startrails back then.
 
In digital, you simply have to make a series of exposures. and assemble them in software. Certain cameras have an intervalometer function built in, where you can tell it to tak some number of pictures at a set interval between shutter firings, and you just set the camera on the tripod and go find something to do for a while.
 
G'day Ron

This is my first posting on this site -- so I hope that this response is not too late for your after-dark activities. (As per my profile, I have been a forum user elsewhere for many years)

You are asking about Bulb + stacked exposures + sensor issues ... so may I respond with my experiences

A decade ago I had a Pentax and its B setting stopped after about 4-minutes ... so it was useless for stars. The Pentax was sold soon afterwards too :p

Over the last decade or more I have used Panasonic fixed-lens superzoom (bridge) cameras, and they perform beautifully. I regularly take 3- to 5-hour star-trails images with exposure times of 30 to 60 seconds x 300 to 1000 images (ie: till the battery goes flat). "M" mode x 30-60s x F2,8 x ISO-800 gets some beaut images that are stacked via "Startrails.de" software. I did one a couple of nights ago and the 300 images took 10-minutes to be stacked

I just use the camera's internal shutter timings, no need for external gadgets, any NR options in the menu settings are cancelled (experience shows little to no difference when it is activated)

As to sensor 'fading' or 'burning' etc.... if a $500 'bridge' camera can shoot 1000 continuous exposures without any issues, your dSLR should be more than happy to give you some excellent results

Hope this helps
Phil from the great land Downunder
 
Phil, Welcome aboard. Lots of good folks and information here.

Stacking photos seems to be the normal method to doing star trails. However, though my Canon T6 can take multiple photos for action scenes, with each push of the button, I cannot control the time between each shot nor the time between the pressing of the shutter.

It would be possible to stay up all night and press the shutter at some pre-determined interval to optimize exposure and sensor cooling, But I have a number of of old film cameras I can aim at the north star, set to "B" or "T" and set the alarm to wake in up in 3 to 4 hours.

My biggest problem lately had been the weather, haze, clouds, heavy dew and full moon.

Good luck,
 
G'day Ron

I might have missed explaining something here / above :(

There are two steps that are needed as well .... a) set the shutter to "continuous" mode -not- single image mode, and b) use a remote control device plugged into the camera before it all starts

When using the remote control device, if you slide the remote trigger into the 'locked' position, then the continuous setting for the shutter keeps on clicking away until the battery goes flat

Hope this helps
Phil from the great land Downunder
www.flickr.com/photos/ozzie_traveller/sets/
 
The T6 does not have an intervalometer built in, but there is an external controller available that serves that function.

Ozzie's method might work, if the remote trigger can lock to always pressed for the shutter release. That was easy when a remote was a cable with a button on the end and a set screw on the button you could lock it with. An electronic remote may not have that, in which case you're back to interval timing. The shutter trip interval needs to be a second or 2 more than your exposure time, to give the camera a chance to store the image. In other words, you can't trigger 30-second exposures every 30 seconds; it won't be ready, and it won't trip the shutter until the next 30-second interval elapses, leaving you a 30-second gap. I trigger a 30-second exposure every 32 seconds.
 
Go to the source:


A couple of things that are missed here.

Heating up is in direct application of the idea that heat is being transferred through the system via electrical conductance.

Because the batteries are of a typ. lithium style, overheating if over taxed is quite possible.
But long exposures don't cause that typically unless the sensor is drawing huge amounts of power.
(Phase One p20).

The draw by the sensor is minimal and if Canon sets the timer up for "Hours", I think you safe unless your shooting at the equator.

The other aspects is the amount of light, and both visible and invisible light the sensor is picking up.
(IR and UV). The IR is highly filtered due to the filter in front of the sensor to cut down said IR light.

There are tons of advice on this in many forums, the internet and books.

Your core issue on heat is simple: The body of the camera.

I would be more worried about stabilization of the camera to eliminate shake more than heat.
 
G'day Ron

May I insert one of my star trails from several years ago
It is a 6-hour long exposure of 500 individual images @ ISO-1000 ~ the camera being the Panny G2 (m4/3 sensor) using the 14-42 lens at 14mm / 28mm FFequiv

The night was late summer / early autumn, with a full moon, occasional clouds and no mist or dew to worry about and the camera continued shooting till the battery went flat. For me checking on the tripod + camera every 1/2-hour or so, there was no heating or other issues to worry about ... other issues being spiders who decide that the tripod is a beaut place to create a new home for themselves!

Phil
zBowenville Q 6hrs x 500pix [full moon, ISO-1000].jpg
 
I know this has gone into many variables and answers, but this is what I wanted to write and I'll try to keep it simple?

In digital, you simply have to make a series of exposures. and assemble them in software. Certain cameras have an intervalometer function built in, where you can tell it to tak some number of pictures at a set interval between shutter firings, and you just set the camera on the tripod and go find something to do for a while.

YES!

Set the camera for 30 seconds and lock the shutter release down. That's usually the longest setting available. You can use a remote release and if a camera doesn't have one, a C clamp. (a little over the top, but the point is, the camera will take and process the images as fast as it can, until the battery goes dead) And in that case, use an external continuous power source. The camera will take images until the card fills. And if you have a large enough card, the camera will take one image, every 30 seconds, then process (so that time is lost) and then take another 30 second exposure. No interval timer needed.

You can shoot from dusk to dawn and throw away the ones you don't need.

Full Moon during Perseids, but I finally have a battery powered version. Maybe Saturday night?

night-sky-on-lake-shore-2022.jpg


Not in the potential roadblocks mentioned (I may have missed that) is dew, which except under ideal situations, especially near a lake, is also going to ruin the sequence. Yeah to bugs, fireflies, and spiders. Airplanes, satellites, and the International Space Station and Starlink.

No I haven't had a camera burn up doing this... yet.

moon-and-stars.jpg


One not enough? :disillusionment: Each one has a hand wound heater coil on the lens.

I hope that was helpful and details if anyone wants to know. Yes I am having fun.

Lock the shutter release, with time set to 30 seconds. You could do this with a pocket camera and a battery eliminator.

Before someone says how wrong that is, that would be for a point and shoot camera that does not have manual. Or an any camera, work around, it’s possible but not the right situation.
 
Last edited:
Manual = A place to start.

1 turn off long exposure noise reduction, or any high ISO noise reduction.
2 turn off the display & review
3 incandescent
4 iso 3200, f/wide open
5 manual focus, set to a spot of light not just turned all the way towards infinity AF off
6 empty card, full battery, external power source is best
7 lock shutter button down with a remote cable release
8 shutter speed 30 seconds

if you start the camera just after dusk, you can go and watch a movie go to sleep, get up at sunrise and it should still be shooting pictures.

or as the alternative if there is not an external power source, when the battery dies, and a grip would have two batteries, or when the card fills.

Jpegs process faster, take less space.

The camera will take a 30 second image, then process for a few seconds, then immediately take another photo, process, photo…
 
G'day Pete

Your info above added to mine should go a long way to making it easy for others
One thought re your final sentence above ... The camera will take a 30 second image, then process for a few seconds, then immediately take another photo, process, photo…

My Panasonic cameras have zero time lost between exposures ... both the G-2 (now over a decade old) or the newer FZ-2500, each exposure ends and the camera instantly starts the next. ie- 30 seconds--click (to end exposure)--clunk (start of next exposure) sort of thing

ps- I like your lens heater arrangement ... we don't need stuff like this Downunder !
Phil
 

Most reactions

Back
Top