Botanical Time-lapse tips. Part 1) Dealing with Flicker

Hello folks!

I hope you have all been well! It has been a little while since I put up a blog post. Lack of time would be the reason. Summer is coming, nurseries are selling more plants which are getting ready to bloom, and there is just a lot of shooting to do, and I am not the only one doing this stuff either. It seems to have been a… blossoming (hahaha) of other time lapse photographers that are giving a hand at botanical timelapse photography! I am very excited about this too! I love seeing how other people go about things and I love watching their results.

I have a lot of information buried within this blog, and figured maybe it would be nice to put out a Tips & Tricks blog for the aspiring botanical time lapse photographers. I have been focusing on plants now for 4 years, I have learned a lot, made many many many mistakes, some of them pretty costly, and if I can help others out to save them time, money, and energy, well, that’s what I love to do.

 

Avoiding Flicker

The most common issue I see with botanical time lapse is flicker. Many of the photographers experimenting with this seem to have flicker to some degree, and there is just no need for it. None of mine have any flicker whatsoever since 2014, I never use de-flickering software, and I am happy to share my secret.

It took me a while to figure it out, but the flicker can be a combination of several things. Bulbs not warming up, exposure inconsistencies, lack of control of light in a room. This is the most common thing I have seen on many of the new botanical time lapses I have seen.  So lets just go ahead and crush this one now and you will NEVER have annoying flicker in your time-lapses again.

Lighting

I only use LED lighting. I have tried many forms of light.  Traditional bulbs. Florescent. Strobes. Speed-lights. None of these in my view are very good.

  • Bulbs work “OK” However as they warm up I sometimes run into color shifting which can cause some white balance flicker. if the bulb is on NON-STOP it works pretty well, but if you have it on steady through the day then have it turning on and off during the night cycle, you will probably notice a slight hue shift during the evening. The on-off switching can take its toll as well, and there may be some overall dimming. With bulbs its best just to turn it on and keep it on the entire time, this is good with shorter timelapse sequences, but shooting much past a few days the plants will become distressed.
  • Florescent. Sort of the same as bulbs, but worse if you run them constant for a day cycle then turn them on and off for night. There will be some very heavy issues with exposure as it takes several minutes for them to get to max brightness.  Works OK if you are just doing a few days of shooting.
  • Studio Strobes. When I first started I was using some Elinchrom studio strobes. At first I actually had pretty good results, but after a while the bulbs in the strobes started to be less and less consistent as they aged.  I am not sure how may shots you should be able to get with a tube, but a week of shooting will rack up hundreds of discharges. If I remember correctly, after a few thousand discharges I started getting quite a bit of flicker.
  • Speed-lights, same issues as with the Studio Strobes but you also have to keep replacing the batteries. No good for this work.
  • LED. Yes. This is it. This is what you want. LED Lights. Nothing beats them for this type of work. There is no warm up time, they produce very constant and even lighting. you CAN still get flicker if you are shooting with a fast shutter speed and using PWM. But this is easy to overcome. You can turn LED on and off as many times as you want, the output is always the same.  I only use LED period. If you look at my work over the last few years, there is ZERO flicker, and much of this has to do with the LED lighting.  And the best part is the LED lighting does NOT need to be expensive, and high power LED is useless for the time lapse portion (but it is beneficial for macro video work). So there is really no need to go run out and spend thousands of dollars on LED panels. I use 2 cheap ones off amazon and cost me under $100 each, and even then I spend more than I probably needed.. Look for something dim-able (pwm is fine unless you are doing video).

Shutter Speeds. 

Woah there buddy. Slow down. The plants are barely moving. Fast shutter speeds are your ENEMY.  Let me explain why. Shutter speed is usually pretty constant, however there can be very minor inconsistencies on the speed of the shutter.  I am going to throw some numbers out just to demonstrate why, but these numbers should be taken with a grain of salt as they are probably inaccurate in reality, but accurate for the example.

1/1000th of a second is a single Millisecond.  Lets say your camera shutter has a variance of 1 millisecond.  When shooting with speeds of 1/10th of a second, that means your shutter speed would be anywhere between 99 to 101 miliseconds. So you have a variation of approximately 2%.

If you take an image, and make a 2% exposure adjustment in photoshop, you can see the difference between the two images. This is what causes shutter speed Flicker.

Now lets move that shutter speed to 1 second.  That means with the 1 millisecond variance your shutter speed is 999 to 1001 miliseconds, meaning you have a variation of approximately 0.2% instead of 2%.  That 0.2% exposure adjustment is far more difficult to see than the 2%.

Of course, camera shutter speed variances are far less than 1 millisecond, as most cameras can shoot 1/4000th of a second and faster with pretty consistent looking results.

PWM Flicker

Lets say you are using LED lighting. It may be a voltage regulator adjusting the brightness, but many use PWM to adjust brightness, which essentially is just making the light work like a strobe so fast that it seems solid. This shows up on video quite often as rolling lines of lighter and darker areas due to the way the image sensor pulls its data.

Lets say you have your LED’s nice and dim, 10% and 20% power.  What you see below, the x shows when the LED is off, the 1 shows when it is on.  10% has half the number of ON as the 20% making it 1/2 the power.  100% means it is steady on.

10% = xxxxxxxxx1xxxxxxxx1xxxxxxxx1xxxxxxx1
20% = xxxx1xxxx1xxxx1xxxx1xxxx1xxxx1xxxx1xxxx1
100% = 11111111111111111111111111111111111

If the LED cycles 100 times, at 10% during a 1/100th shutter speed, you will get variance as sometimes you will get the LED on 99, or 100 times during that exposure, it depends where in cycle when the exposure starts. This gives a 1% variance that can potentially show up as flicker depending on how many times the LED burst while the shutter was open.

if you have a 1 second exposure, the LED would pulse on about 9,999 to 10,000 times during that 1 second, meaning the variance is substantially lower, meaning a far smoother output with virtually no visible flicker.

(once again, numbers for illustrative purposes only)

Aperture. 

I shoot non native lenses. So the aperture is locked in place the whole time,  but just light shutter speed on native lenses there WILL be some aperture slop that will cause flicker. This is well known within the landscape timelapse community, and many people use Nikon Lenses adapted to whatever body you are using.

Light pollution Flicker

This one you have to get a handle on, even if just shooting for an afternoon. My recommendation is a windowless room, or blackout curtains. Any light from the outside can mess things up due to clouds, reflections, sunny morning and cloudy day, etc.

if you are unable to get some space with complete light control you might want to look into shooting within a grow tent, they provide excellent light control to prevent light contamination from the outside world.

If that is not an option, you might just have to look for a day where the forecast shows full sun and keep the shoot to mid-day. there are quite a few flowers you can find that will bloom in less than an hour such as daffodils.

Easy breezy

In the end, the recipe to 100% completely eliminate flicker is simple. LED lighting. Slow shutter speed. Locked Aperture.

When shooting plants often you are using close focus or macro lenses, so it is far more beneficial to shoot at f/16 or f/22 for the larger depth of field (area in focus), which also makes it easier to use longer shutter speeds.

When I am shooting my LED panels are normally at about 10-20% brightness. My shutter speeds are always longer than 1 second. My aperture is almost NEVER wider than f/11.

Oh and one more benefit of a slow shutter speed, if there are any tiny bugs flying around they wont show up in the image.

 

Hopefully if you are into botanical time lapse and have been running into issues with flicker this may help you out.
I will be doing a few more of these blog posts in the next few weeks. If anybody has any topics they would like me to cover let me know. 🙂

4 thoughts on “Botanical Time-lapse tips. Part 1) Dealing with Flicker”

  1. …hey Chris, great post but I have a question…what does PWM stand for? Also, I have a grow light on 24/7, is this not good practice? I usually shoot for 5 days at a time…

    Thanks!

    1. Hi Michael!
      PWM is Pulse Width Modulation. You have several ways to dim LED lights. The best way for video work is simply to lower the voltage to the LED so they do not put out quite so much light. Another way is to use PWM, which turns the power on and off very fast, this result is a dimmer LED as the power is not on enough for it to hit full brightness before it turns off. For general photography this does not matter, but with video this can become a concern with faster shutter speeds. Here is a good article on B&H that explains it better than i can

      As for the grow light on 24×7, I plan to discuss that in an article today 🙂

  2. 1. Do you find blooming plants generally require the lights to go off for apx 6-8 hrs at night?

    2. Do you have any way of saving space on your camera by having the timelapse automatically pause for these hours?

    I am currently using Magic Lantern on a T2i

    Thanks!

    1. Alexander, My apologies on the delay of reply. I dont get notifications for posts on here, i will email you as well.
      Blooming flowers do not really need day/night cycles. You can get by with constant lighting, but if you have to shoot much more than a week the plant may get stressed and start having problems. I built a timer system that controls both grow lights and fill lights, it will shoot 24×7 but it shuts the grow lights off before it takes an image, and allows for day/night sessions with the grow lights.

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