Timelapse shutter speed rule of thumb explained

The widely accepted rule of thumb for shooting timelapses is that your shutter speed should be 1/2 your interval. What this means is if you are shooting one shot every 3 seconds, then your ideal exposure is 1.5 seconds.

WHY?

The point of shooting timelapses is to end up with video at some point, right? Film cameras have dealt with this issue for some time now. In a film camera, a piece of film rapidly advances one frame, stops, is exposed to light, then the exposure stops, the film advances and the whole process begins anew. This process can occur 12, 24, 30 or more times per second. The camera needs some time to move the film into position, so it spends some time with the shutter closed (moving film) and then it spends some time with the shutter open (exposing film) The standard for a long time now has been to spend half of the time exposing, and half of the time moving film (not exposing.) On film cameras the shutter is often on a shaft and rotates through the film plane. Thus a 180 degree shutter literally is a half circle that blocks the film from getting light half of the time.

180 degree shutter

WHY?

Well, that’s still a good question. Digital cameras can go from practically 0 degrees up to literally 360 degrees. The big difference is in what it looks like. Motion blur is what this is really all about. Regardless of your exposure or frame rate, a shorter exposure will have less motion blur on it. On the flip side of the coin, a longer exposure will have less action occur when the lens is ‘closed’ and it will look less strobe-like. The balance between those two things is how people decided on a 180 degree shutter, and that brings us back to shooting stills.

When shooting a timelapse, if your shutter speed is smaller than half of your interval then your video will start to look strobey. What I mean by that is that there is a continuity gap from one frame to the other. If the video is of a car driving, then the distance that the car moves between frames will increase and the resulting video will look jumpy.

If your shutter speed is larger than half of your interval you will end up with more motion blur. Trails will occur behind moving objects. This is generally less of a concern because our minds are much less confused by trails than by strobing. Strobing can be dissociative, while motion blur is more like an artistic statement.

In conclusion: Like all rules, this rule of thumb is meant to be broken but it can never be ignored.

Addendum: When you are shooting video in movie mode, this should also guide your shutter choices. If you shoot 720p 60, then you should have a shutter speed of 1/125, and if your are shooting 24fps, then it should be 1/50. Feel free to deviate but know what will happen if you do.

How to easily test in-camera sd card speed

This is a cross-post from my other blog you down with fcp because it seemed just as applicable here. Go there for final cut pro related tidbits!


I picked up a canon t2i the other day to save some timelapse-related wear and tear from my 7D. Unlike the 7D, the t2i uses sd cards. I was really happy to find out that sd cards in general are far cheaper than CF cards, but I quickly realized that some cards are better than others, even when they have the same specs. I was inspired by this post over on peta pixel to run a quick test. This isn’t a very broad test, but I tested all the cards I could scrounge up.

In order to do this, I just popped in an sd card and fired off 15 shots. I recorded audio of the camera firing and then compared the waveforms in final cut.. The quick cards bogged down significantly less than the slow cards. You can see the in-camera buffer get filled up after 7 shots, and then the real test begins. The gap between shots is now due to the write speed of the card. The end of the green bars represents the total amount of time that the card spent writing buffered data. Since I didn’t line them all up starting at time=zero the numbers to the right of the green bar represent the total time to shoot 15 shots.

Results:

Sandisk extreme class 10 45mb/sec 32 Gig – 9 Seconds

PNY professional 20mb/s 32 Gig – 15 Seconds

Sandisk Ultra II 2 Gig – 17.75 Seconds

Sandisk 1 Gig – 26.20 Seconds

 

What does this mean? Well, it shows the comparative speed of different cards I have available to me. You may get drastically different numbers based on your cards and cameras, but you will probably still show the same trend. I wouldn’t even think of using the slower smaller cards for video, but this certainly puts some data behind that feeling. For stills the speed really doesn’t effect me very much, but it is crucial for video. If I’m shooting hd with a high iso (lots of detail make a hard to compress image) then I absolutely need to have a fast card. Of all of the cards tested, the Sandisk extreme class 10 45mb/sec is a clear winner for dslr video. It is 166% the speed of the pny card, despite only being 120% the price. If I were a stills-only shooter, then I would consider trading volume for speed.

In the future I’m interested in testing out different priced cards in the same class to see what the speed / price curve looks like. Lastly, it brings up the interesting idea that a slow enough card can almost replace an intervalometer. My super old sandisk 1Gig card took almost 3 seconds between shots! That could make for an acceptable time lapse interval in a pinch. Do you have a brand that you love or hate? post it in the comments and I’ll try to see if I can test it.

Note – I know that there are much more precise ways you can actually test cards using a computer. I don’t want that. I wanted to test both my camera and sd cards simultaneously.

star trail stacking in photoshop

flattenedFullframe

I have always wanted to do this kind of photography, but with most digital cameras there is simply no way you can leave the shutter open and the sensor on for a few hours. My D40 starts to get some serious noise after a few minutes, and there clearly must be an upper limit due to the sensor overheating. Luckily for me there is a relatively simple way to compose LOTS of shots into one image and achieve the same effect.
For those who only want to mile high review of it, here it is. Take a ton of pictures with a long-ish shutter speed. (for this one I used 10 seconds) and then layer them all in photoshop on top of each other and use the
“screen” blending mode to get them all visible.
The actual application of this can be difficult, because it is either REALLY time consuming, or it requires some thought and scripting. I decided to go for the latter and use my noggin a bit.

Scripting a photoshop action.
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nikon d40 camera external power supply hack

d40powercord crop

I have been looking for a way to add external power to my camera for a while. I have had some good ideas and even hacked together a workable prototype a while back. The problem was it wasn’t very ‘tight’ and I was always afraid I was going to reverse polarity, or short it out, and it took a lot of time to set it up every time I wanted to use it.

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$17 Arduino-based nikon IR intervalometer + code

invervalometer_4

This is one of those projects I’ve been working on for quite a while now, but never well enough to actually put it in a box! Well.. it still has no box, but it’s much closer to a boxable form.

It is a RBBB arduino clone (but any arduinowillwork) with an ir led, a potentiometer, a resistor, and some perfboard. The perfboard is as much there to help provide a little bit of wire strain relief as it is to provide a place to mount the pot. The code simply reads the pot input and converts it into a delay() function. Then it fires the IR led with the nikon-specific magic to tell my d40 to shoot.

Here is an example of one of the timelapses I have shot.

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CHDK Update

chdk_splash screen

So as I referenced in an earlier post, I bit the bullet and bought a camera so I could test out CHDK. CHDK is a hacked firmware for canon cameras that use one of three imge sensors. I believe it is the digic 2, 3, and 4 sensors. It turns out that all of the powershot line uses the same image sensors. The optics, buttons and features are added or removed based on the price point of the camera. If you use CHDK you can enable them AND add new features the designers may never have thought of! click here to find a compatible camera on amazon More info about my trials and tribulations after the jump.

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How to use Ac power to replace the Nikon D40 battery

I still haven’t gotten the grip I mentioned a few posts ago. I don’t know if I will. I have figured out a clumsy hack to get the job done and I might just run it this way, or perhaps clean it up a tiny bit.

This is the battery with little aluminum strips taped to it. The battery compartment is too tight for regular wires, so foil was the only way to do it.

aluminum foil wiring for battery pack d40

aluminum foil wiring for battery pack d40

This pic shows the “wires” coming out of the battery grip. I have alligator clips on a 7.3V 200Ma cell phone charger. I connect it to the foil and off we go!

battery grip showing aluminum "wiring"

The reason why I have the battery in there is because without it, there isn’t enough juice to fully actuate the shutter. I think that some kind/type of capacitor would also do this, but I’m afraid I don’t what kind would work.

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Arduino Intervalometer for my Nikon d40

After seeing this project from cibomahto a while ago, I finally got my act together and bought a $1 IR led from radio$hack so I could build an intervalometer for my SLR.

For those who don’t know an intervalometer is, it tells your computer to take a picture every given interval. This enables you to shoot video with a still camera over a long period of time. Sometimes you have two intervals on fancy ones. Those allow you to use the bulb setting on your camera. Right now it has two potentiometers to indicate seconds and minutes between shots. It is run from a nine volt battery, and I expect it to have fairly good battery life. Only time will tell. The IR LED can’t take too much juice! It has a status led to show when it is firing (for trouble shooting) and not a whole lot else.


This currently needs a housing and a interface. I am debating the merits of a small lcd vs just using a printed label to mark the pot positions. It’s pretty much spray and pray right now. At least it is adjustable!

arduino d40 ir intervalometer

arduino d40 ir intervalometer


I’m thinking about getting one of these and eliminating the pots completely.


lcd shield from nuelectronics.com

lcd shield from nuelectronics.com

Which would end up making my project very similar to this one but for a nikon.


One last thought is possibly adding the functionality to use the bulb setting and then add a bracketing ability. Isn’t technology wonderful!

Time Lapses

I had a lot of time to kill over break, so I shot a bunch of timelapses. Here they are!

This is from a coffeeshop that I spent a lot of my time in.

This is of some clouds at dusk. This one has two separate positions, and it is really interesting to see the color shift towards the end of the video. I also have it on auto-something(ISO?), so it isn’t very consistent frame to frame.

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7 questions for my avid fans

Seeing as how I am constantly inundated by media requests – I figured I would use my podium here to ask the readers a few questions. I look at it as distributed googling really, and hopefully finding some vetted answers in the sea of confusion that is out there.


1) has anyone used CHDK here? It is a modified firmware for certain cameras, and seemingly it allows you to get very low level access to the camera. With it you can enable time lapse mode, Raw shooting, video, motion detection, and I think they are working on time travel. This seems like an amazing project. Does anyone have any success with it? Does anyone have any recommendations on cameras? Im kind of looking at the SD1100 and the SD600.

and lastly, does anyone have any recommendations on where to find said camera cheaply? I’m running dd-wrt on my home router and have a hacked xbox, so this seems like it is within my reach, just looking for people with experience in it.


chdk interface

chdk interface


2) does anyone know of any good anti flicker plugins for after effects (or anything else (on a mac)) that will remove the frame-to-frame luminance variations of a dslr time lapse?


3) does anyone know why frame-to-frame luminance variations happen on my d40 running in complete darkness with a manual lens and a flash?


4) does anyone know of a good guide to moving an arduino project towards a mass producible item? Lets say I would like to make a one board version of my arduino rss reader – how would I go about doing that?


breadboard arduino

breadboard arduino


5) How much does the average human heart weigh?


6) Does anyone know of a comparison between the online stock video sites from a submitter’s perspective? Does anyone have experience with any specific sites? (feel free to email me if you would rather not post publicly – “r” at this domain, no prefix.)


7) Enough about me – Why are you here? What kinds of projects brought you here, and what kinds of projects would you like to see here?


Thanks for your time, and hopefully your answers!