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.

What do vendors gain by making closed hardware?

I have a Hp mini netbook, an xbox, a canon 7D dslr, a canon powershot point and shoot camera and an iphone.
The netbook is a hackintosh.
The xbox has a mod chip so it can act as a media server.
The powershot is running CHDK which enables an intervalometer and motion detection.
The iPhone is jailbroken so I can run non “approved” apps on it.
I paid full price for all of those devices and I haven’t caused any direct monetary loss for the producers of those devices. I consider that a win-win situation. The hardware manufacturer makes good hardware, and then I am able to do something with it that was not initially considered by the manufacturer. I paid for it, I should be able to modify it.

When I bought the 7D I knew that there was a ‘hacking’ effort underway and I was looking forward to some day when it would bear fruit. I have checked in every few months since then and I finally realized that instead of bearing fruit, Canon has killed the tree. With each consecutive firmware update, canon has locked the hardware down more and more. They have made it harder to develop for and now it is at the point where development has stopped. How does this help canon sell even one more camera?

I honestly don’t expect them to go out of their way to help us hack their hardware. I do expect them to help their bottom line by making innovative hardware cheaply, and making it as flexible as possible so that huge numbers of people buy it. Their continued efforts to encrypt and lock down the firmware on their cameras confuses me because their cameras still have a lot of flaws. The time that their programmers and engineers put into “locking the gates” could have been spent adding audio levels, reducing shutter effects, or enabling a record time greater than 12 minutes! As a law abiding purchaser of their hardware I am really offended. I am offended that they went on the attack instead of graciously acknowledging that their cameras are the focus of some innovative creative people. I am also saddened because I can not think of a way that it is good for the company, or the consumer, or the industry. This seems like equal parts greed and ignorance.

If you understand why they do this, I would love to hear it. If not, then I’m sure canon would love to hear it.

Public Relations Department
Corporate Communications Division
One Canon Plaza
Lake Success, NY 11042
E-mail: pr@cusa.canon.com

Weird banding on Canon 7d explained!

The other night I was out filming traffic. I ended up getting a really weird camera artifact. It looks like a dark bar that rolls through the shot from bottom to top. At first it made me freak out a bit, thinking that the camera was somehow broken. I eventually figured out that it is the result of A) a flickering light source and B) the right (wrong) shutter speed. I think the streetlights were tungsten bulbs, but they may have been HID bulbs. Whatever they were they definitely had a flicker to them.

I read somewhere that ideally you should shoot a shutter speed that is double the frame rate. This gives you a 180 degree shutter and it should look very similar to film. The way that I made these bars appear was by changing the shutter speed away from 1/125 when I was shooting 720p60. I have ideas as to why this creates the banding, but they are all theories. If you have any more insight pleas tell me in the comments!
Moral of the story: keep the shutter speed at twice the frames per second. Change the aperture, or buy a faster lens!

good gear to go with your shiny new canon 7d


I can only hope that there will be a lot of other happy people unwrapping new cameras this christmas. I bought my 7d about a month ago, and the best/worst thing is that now I realize buying it is just the beginning. I want to buy sooo much gear to use with it, and it is tough to find well recommended, modestly priced gear. Here is the short list of what I have or want to buy, to wet your creative whistle.


bogen tripod with fluid head.
If you buy nothing else on this list, get a tripod and a fluid head. The 5d/7d do not have ANY image stabilization capabilities, so if you plan on using any lens longer than a 50 you will need to use a tripod. The fluid head is also critical because many other types of heads are built for still photos. They are easily adjustable, but not in smooth movements. A fluid head is designed for video, and is the only real way to get a smooth pan.

Hit the MORE for more!
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Slow motion from the 7d. 720p60 to 24p How-to

There were a few different stages of excitement that I went through after getting my Canon 7d. First I played around with all of my manual nikon lenses (using an adapter of course). Next I marveled at the settings and the live view feature. Finally I decided I wanted to go out and shoot some slow motion video. This is fairly easy to do seeing as the camera shoots both 720p and ntsc at 60 frames a second. The software side of slowing things down required some thinking, but it’s easy once you get the hang of it.

Here is what I (and the wisdom of the internet) have come up with.

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Canon 7d test video

canon 7d test shoot

here’s a quick video I put together with my new dslr: the Canon 7d. I’ll run down my gear and workflow in a lil bit, but for now, here’s the vid.
Canon 7d test / Coffee facts

Cheapest follow focus ever for canon 7d / 5d mark II

51W5SN8J+lL._SL160_

Ever since I have fallen in love with the Canon 7d dslr, I have been fantasizing about making a legit follow focus for a dslr. It allows you to have more control over the focusing, and a smoother camera because your rotation is in a different axis as the lens. (You may hear more of my traditional FF plans in a few) In the meantime I saw a vimeo clip that had this little gem of an idea in it. For quick focus pulls a lever like this can’t be beat, and it’s dirt cheap as well!
rack focus for canon dslr

Here are all of the parts from the old home depot. Simple stuff. It totaled around $6, and it’s enough to make 2 and have parts left over.

worm screw

The first step is to cut out a few teeth in order to make room for the bolt.

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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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