Issues around access to menus and user guide

[Rcon]

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Love my new SL2 and 50mm summicron

however as new to mirrorless attaching my new flash was a challenge - on my Nikon D850 flash TTL was plug n play and simple to use but nowhere in the SL2 user guide for camera or flash does it say select mechanical setting for flash - how remiss - as new to mirrorless I assumed that a sensor would be smart enough to replicate curtains  - In addition, in the world of IT when asking a factory reset its usual to have 2 simultaneous actions - reset in SL menu is very tricky - two accidental rolls on the menu and all settings disappear - we need a positive process that is not prone to accidental or clumsy use when resetting - it must be a deliberate action

 

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[Jared]

If you get a set of settings you like, I would recommend exporting them to a flash card and then backing them up somewhere.  It can save a couple of hours of work later trying to remember exactly what you put in each preset.

As to the requirement for mechanical shutter for flash to work, that isn’t something that can be replicated with electronic curtains.  You would need a “global shutter” not just an “electronic shutter” for this feature.  Same limitation for other makes of camera. Here is how electronic shutter works in general... 

Reading out a full chip takes perhaps a twentieth of a second or so.  From the time the electronic shutter starts until it completes the pixels are light sensitive.  So each exposure with the electronic shutter is actually about 1/20s in duration.  So how do they get exposures shorter than 1/20s? And how do they make sure all pixels get the same amount of exposure rather than the ones that are being read out first getting less than those that are read out last? They use a “rolling shutter”.  That is, they stagger the start for each row.  They start each row the right amount of time before they are going to read it.  So while the whole process may take 1/20s, each row of pixels can receive light over a shorter (or longer time). 

The catch is that there is no period of time in a short exposure when all pixels are sensitive to light at the same time.  Each row might get light for, say, 1/100s, but the first row gets its light much sooner than the last row.  A flash might last for just 1/4000s.  When would it fire?  During its duration only a few rows would be active.  Hence the need for a mechanical shutter.

Even mechanical shutters have flash limitations.  You still need a period of time when the entire frame is exposed to light all at once so that the flash can go off.  The first curtain opens (over about 1/300s in the case of the SL and SL2), then the camera waits, then the second curtain closes (again taking perhaps 1/300s).  If you want a shutter speed faster than 1/300s or so, you start the second curtain closing before the first curtain has finished opening. Effectively, a slit of light travels in front of the detector.  The faster the shutter speed the narrower that slit of light and so the less light each row receives.  Just as with the electronic shutter you need a time when the shutter is completely open and the second curtain hasn’t started to close.  The time when the shutter is open and “waiting”.  That’s when the strobe is triggered.  All pixels get light.  The fastest shutter speed where there is a “waiting” period between first and second curtains is the sync speed.  On the SL2, that’s 1/250s.  That’s how I know the approximate time it takes for the curtains to move, by the way.  If they took much more than 1/300s there would be no “wait” time at a shutter speed of 1/250s.  If they were much faster, then then the sync speed would be higher. 

What about high speed sync?  How does that work?  Instead of setting off the flash for a very short duration the power is lowered and the flash is strobed over a few hundredths of a second to allow light to reach the chip for the entire length of time it takes for the shutter slit to cross the film plane.  In theory that could probably work for electronic shutters just as it does for mechanical, but I haven’t heard of anyone implementing it.  In any event it has some real downsides.  The biggest of these is dramatically reduced power for the flash.

Why doesn’t the manual contain a note saying mechanical shutter is required for strobes?  Don’t know. It should. I didn’t realize they had missed that.

[Jared]

Oh, forgot to mention leaf shutters... The reason they generally have no maximum sync speed is that all pixels receive light at the same time regardless of shutter speed.  As soon as the blades start to open all pixels are equally illuminated.  Hence, no sync speed.

So why not use leaf shutter instead of focal plane shutters? They have disadvantages, too.  They add to cost since a shutter must be included in each lens, and they won’t go as fast, usually maxing out at 1/2000s or so depending on the physical size of the opening.

[Jared]

By the way, I did find one place in the manual that mentions the need for mechanical shutter.  In the frequently asked questions section under “flash won’t fire” it says that electronic shutter is not compatible with flash. It’s on page 202 of the English language user guide. Not the most obvious place to put it, of course.