SmaTrig 2.1

Shutter lag measurements - Canon EOS 400D / Digital Rebel XTi

After triggering a camera (mechanically or electrically) it takes a certain time until the shutter opens and the exposure can begin. This delay is called the shutter lag. The values vary strongly depending on the camera model. The focusing time is not considered in this test. In all test images the focus was adjusted manually for fastest response times.

There are several ways to determine the shutter lag of a camera such as photographing falling objects, rotating discs or an electronic counter. I chose the digital method, due to a simple implementation and good readability of the results. To implement the timer I used my FPGA board on which I implemented a binary 8-bit counter with a time step of 1 ms. This counter was connected to 8 LEDs showing the time elapsed since the triggering. The camera was triggered by an optocoupler to reduce the risk of damage. To record the time stamp the camera was set on manual focus, 1/1250s, f5.6, ISO1600 and pointed on the counter. Having everything working properly I shot some series of test pictures. An example is shown below.

shutter lag setup

Results for Canon EOS 400D / Digital Rebel XTi

The shutter lag was measured with and without mirror lock-up. To make the results more reliable both test series consist of 16 images. Pictures with ambiguous time steps due to a jumping counter were sorted out before the analysis. The results are shown in the histogram below.

shutter lag EOS 400D

The bars correspond to the frequency of occurrence for each shutter lag value. The shutter lag varies around 115 ms for the case without mirror lock-up. Enabling the lock-up mode reduces the lag almost by a factor of two to about 66 ms. An interesting fact revealed by the test is that the shutter lag is not constant. A lag of 65 ms is an average value, but good enough to use the camera with a lightning trigger. A microcontroller based DIY lightning trigger circuit using mirror lock-up is described here. I also measured the minimum trigger impulse duration for reliable trigger operation (see plot below). For pulses shorter than approx. 15 ms the trigger failure rate increased rapidly. The results with the corresponding timing diagram are summarised below.

timing diagram
minimum trigger time tt 15 ms
shutter lag w/o mirror lock-up td 116 ms
shutter lag with mirror lock-up tdml 66 ms


I repeated the measurements later to find out the influence of the aperture setting on the shutter lag. The aperture can potentially increase the shutter lag, because it must be closed each time before the exposure begins. The results were very similar to those described above. The aperture had no influence on the shutter lag.

Comparison of shutter lag and startup times for different cameras


Gray code
Hi! You wrote “Pictures with ambiguous time steps due to a jumping counter were sorted out before the analysis”. At 1/1250 s, it is expected that most pictures show a jumping counter. Did you consider using Gray code to avoid ambiguities?

Also, it should be noted that the measured times can vary by something like 4 ms depending on the vertical position of the counter in the frame.
#11 - Edgar Bonet - 05/27/2016 - 15:28
SmaTrig 2.1 (Nikon D3200)
Just built the trigger and getting use to it. One thing that I have noticed is that it would be useful if the delay function that is available for the light barrier trigger was also available for the sound trigger.
#10 - Colin - 12/22/2014 - 16:36
Shutter Lag
Albeit short this is an excellent article written in a way that most photographers interested in the subject will understand. I would be particularly interested in more details as to how you determined these figures using your FPGA board.
#9 - Graham Gillett - 07/25/2011 - 08:49
Shutter lag measurements - Canon EOS 400D / Digital Rebel XTi
I learned a lot from this post. Thank you and keep on posting more. This is an spectacular blog
#8 - Larry Linet - 04/15/2011 - 11:22
Hi Pascal,

fantastic web site... You gave me new inspirations.

#7 - Luk - 11/11/2010 - 10:22
Fantastic idea with the binary led counter..

Looks like can be ignored
Not even close to a second. IMO can be ignored.

Depends on the purpose.. If you're doing highspeed photography 100ms is huge!
#6 - Pascal Bovet - 11/09/2010 - 21:15
Looks like can be ignored
Not even close to a second. IMO can be ignored.
#5 - freelancer - 03/30/2010 - 10:53
I just was to reiterate what others have said in the previous comments. This article has really been of use to me. I've wanted to know more about lag times and now I do.
#4 - Senior - 12/07/2009 - 17:26
conon 50d and canon speedlite 244t
I have the flash speedlite 244t, can I use it with my canon eos 50d with out fry my camera? it uses two battery AA at 1.5 volts each one with two batteries it will be 3volts. I did try a few times and it worked pretty good but i does not following the comander of my 50d I have to play with my exposure manually, the flash it works directly.
#3 - taly - 10/19/2009 - 18:14
Shutter Lag Time in Teethered Mode?
Thanks. Needed this data.
How about the same data in teethered or triggered by software SDK?
Anyone did this test?
Any idea what is the expected lag time?

#2 - richard - 09/27/2009 - 03:13
flash sync
The shutter lag has no influence on the flash timing. The flash is fired after the shutter opens and not when you press the shutter button.
Using an old flash on a modern DSLR is usually no problem, unless the trigger voltage is too high. Trigger voltages of many old flash units can be found on this great site:
#1 - luk - 07/15/2009 - 10:07
does it also infulance the flash sync?
Hi, first, thank's for your great site and Ideas, I'll try some soon. Does all this have to do with the problem to sync an external flash with my 350D rebel?
Do you have any cirquit to eliminate this problem so I could use my exelent old flash as an external? Thanks, Yoram
#0 - Yoram Peres - 07/11/2009 - 15:13
E-mail (Will not appear online)
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