# 600 EX-RT for fill-in with burst : flash did not fire at each shot...



## Bohns (Dec 9, 2013)

Hello !

First of all, let me introduce myself. I am French, I live in the French Alps close to Grenoble (the 1968 Winter Olympics city), and I have been a photography fan for many years.
Since November 2012, I moved from Olympus 4/3rd DSLR to Canon Full Frame, with an Eos 5D mkIII body and some EF lenses. I shoot mainly wildlife, nature, landscapes and sports, but I intend to dig into portrait and social photography in the coming year.
Two weeks ago, I got a Speedlite 600 EX-RT for my birthday with the ST-E3-RT trigger and an external Battery pack from Godox (Propac PB820).

I spent time to read the instruction manuals and to test this new gear at home. Yesterday, I went playing in the snow with my kids, and it was indeed an ideal case for my first “in real conditions” use. The weather was sunny (so, a lot of light with the white snow), and I wanted to try some fill-in.

Body was set to Av mode, auto ISO, center weighted metering, and equipped with the EF 70-200 f2.8L IS II. Flash was in E-TTL mode, high speed synchronization, and the external battery pack was plugged (Speedlite’s C.Fn 12 set to both inner batteries and external battery pack). I’ve been surprised to notice that when shooting 3 photos in bursts, the flash fired the first shoot, but not the following ones.

I thought that fill-in was indeed allowing burst with flash firing, and that adding an external battery pack would allow faster recycling to ensure even better flash firing at each shoot.
I know that compensating the light due to snow and sunny ambiance requires some power, but I am a bit disappointed here. Is it the settings of my gear, or shall I consider that this case was a bit “extreme” for a first “in real conditions” ? Could you advise me ?

Another question : why, when using a Speedlite with the body in auto ISO, the ISO automatically sets to 400 ?

Thank you all for your help and advices.


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## Marsu42 (Dec 9, 2013)

Bohns said:


> First of all, let me introduce myself. I am French



Fritz welcomes Frog to the forum 



Bohns said:


> Flash was in E-TTL mode, high speed synchronization, and the external battery pack was plugged (Speedlite’s C.Fn 12 set to both inner batteries and external battery pack). I’ve been surprised to notice that when shooting 3 photos in bursts, the flash fired the first shoot, but not the following ones.



Hmmm, even with full power it *should* fire more than one if your battery pack is up to it and properly connected (which the flash doesn't show, mind you). You are shooting at worst-case conditions: hss, fill in snow (= fast shutter speeds = full flash burst). To debug, try shooting at a lower flash output with low fps. And don't forget sooner or later the flash overheats and stops flashing bursts.



Bohns said:


> Another question : why, when using a Speedlite with the body in auto ISO, the ISO automatically sets to 400 ?



Because Canon has a completely braindead auto iso function with flash as you just experienced ... the only way around this is to use Magic Lantern, it has an independent auto iso that works all the time.


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## neuroanatomist (Dec 9, 2013)

As you state, fill in bright light needs more power...but HSS needs more power, too. You were in Av mode, but didn't mention the shutter speeds you were getting. If you were shooting at wide apertures, with sunlit snow I assume they were quite fast...HSS uses even more power as shutter speed increases. Regarding power loss from HSS, Canon states:

[quote author=Canon]
The increased duration of the flash comes at the expense of the flash power, and the faster the shutter speed used, the lower the power. At a shutter speed of 1/500 second, the guide number of the Speedlite is less than half its normal rating, and this drops to less than a quarter at 1/2000 second.
[/quote]

I think the default is ISO 400 with flash and Auto ISO as a compromise between increased sensitivity (to make flash more efficient) and low noise. Obviously, you can select any specific ISO setting you wish with flash, if you don't use Auto.


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## Marsu42 (Dec 9, 2013)

neuroanatomist said:


> and low noise.



Then why is it iso 400 on all cameras (crop, ff) and what about the famed high iso capability trumping the Nikon low iso trolls  ?

Really, there's no excuse I could imagine for this broken auto iso giving the user no options at all. The ML implementation shows that auto iso with flash works just fine w/o a single problem, I've been using it a lot since years from iso 100 to 6400 with m or ettl, local or remote, optical or radio... either there are historic reasons for the flash lockdown or of course configurations or situations I'm not aware of. The power output level is no reason though.


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## neuroanatomist (Dec 9, 2013)

Marsu42 said:


> neuroanatomist said:
> 
> 
> > and low noise.
> ...



Canon seems to start with green square mode, and go from their. When do 'most people' use flash? When the scene is dark. If you meter for ambient in dim light, with default settings and Auto ISO, the ISO will go pretty high - ISO 3200 on many cameras. That's not too noisy on my 1D X, but there's no question that it's noisier than ISO 400. At ISO 100, you are using a lot of flash power - 2-stops more than ISO 400, by definition. 

The point is, if you're using auto-anything, you're trusting the camera to make decisions for you. In many situations, ISO 400 is quite a good compromise between flash power and image noise and DR.


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## Marsu42 (Dec 9, 2013)

neuroanatomist said:


> When do 'most people' use flash? When the scene is dark.



I see your point, but that's what I'm using a p&s flash for, not a multi-flash multi-thousand $$$ dslr.



neuroanatomist said:


> The point is, if you're using auto-anything, you're trusting the camera to make decisions for you.



Your doing this as soon as you enable ettl because it relies on the camera's metering system.



neuroanatomist said:


> In many situations, ISO 400 is quite a good compromise between flash power and image noise and DR.



No doubt, but it certainly is not the only compromise... I even went to the length to improve the Magic Lantern auto iso module myself because I'm usually using fill flash for backlit wildlife, and it's a blessing to have the camera choose iso 100 when possible or higher iso when necessary respecting a min. shutter speed.

I'm really wondering what the reason for the iso 400 lockdown is, my money is on firmware conservatism like the missing min. iso with older cameras or ec in m (tba on the 1dx in 2014 as I read), but then again I might be missing something.


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## Bohns (Dec 9, 2013)

@ Marsu42 : Frog thanks Fritz for the welcome ;D

@ both Marsu42 and Neuroanatomist :
Thank you for your detailed answers.
If I follow (and understand) you, my case is really extreme. Indeed, I tried to keep aperture at f2.8 or f4.0, resulting in speeds over 1/2000 - 1/4000 s. Such speeds do not always allow the flash condenser to refill, even with an external battery pack (by the way, all flash batteries and battery pack were freshly and fully charged). I should have probably set the ISO at 100 or even at the low extension (at 50), to decrease the power needed from the flash for fill-in. Maybe should I have set the flash to manual and set a low power (1/128, 1/64 or 1/32 max), as the purpose was to fill-in the shadows on the kids' faces and quite dark snow clothes.

And I understand from the debate I generated that this ISO auto = ISO 400 is clearly a feature stressing Canon users...

Thank you again, and any additional comment to advise would be fairly welcome


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## Marsu42 (Dec 9, 2013)

Bohns said:


> Such speeds do not always allow the flash condenser to refill, even with an external battery pack (by the way, all flash batteries and battery pack were freshly and fully charged).



I wouldn't say your case is extreme, but one good hint: If you know your flash is maxed out anyway, switch from ettl to full m flash mode because you're saving the power from the ettl preflash for the main flash... it's not much, but every bit helps.

Last not least, if you plan to shoot like this more often, use *two* flashes, reducing recycle times and extending the flash lifetime which severely degrades at 100%, my 600rt just died after 1.5 years (it's repaired on warranty though).


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## neuroanatomist (Dec 9, 2013)

Bohns said:


> ... I understand from the debate I generated that this ISO auto = ISO 400 is clearly a feature stressing Canon users...



Some of them, apparently.


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## Marsu42 (Dec 9, 2013)

neuroanatomist said:


> Bohns said:
> 
> 
> > ... I understand from the debate I generated that this ISO auto = ISO 400 is clearly a feature stressing Canon users...
> ...


Probably some of those who are still stuck to auto iso 400 with flash  ... if everybody else is fine with that they've got that certainly doesn't bother me.


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## alexanderferdinand (Dec 9, 2013)

Pardon me : auto iso with flash?
Didnt even know about that!
Living is learning!

And yes: HSS has less reach/consumes more power.
Could be the reason for the dark second and third frame.

Hello from Austria!


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## privatebydesign (Dec 9, 2013)

Bohns said:


> If I follow (and understand) you, my case is really extreme. Indeed, I tried to keep aperture at f2.8 or f4.0, resulting in speeds over 1/2000 - 1/4000 s. Such speeds do not always allow the flash condenser to refill, even with an external battery pack (by the way, all flash batteries and battery pack were freshly and fully charged). I should have probably set the ISO at 100 or even at the low extension (at 50), to decrease the power needed from the flash for fill-in. Maybe should I have set the flash to manual and set a low power (1/128, 1/64 or 1/32 max), as the purpose was to fill-in the shadows on the kids' faces and quite dark snow clothes.
> 
> And I understand from the debate I generated that this ISO auto = ISO 400 is clearly a feature stressing Canon users...
> 
> Thank you again, and any additional comment to advise would be fairly welcome



Even the 600EX-RT is very limited in HSS at 1/4,000. You have run into a hard limit. Changing iso would not help, if you lower iso the flash needs to output more power, which it can't do, if you lower the shutter speed you need to close the aperture (to maintain ambient) which will need the same flash power. If you raised iso then the flash would not have to work so hard, but again you'd have to close the aperture and that would take back the power you gained. If you used a ND filter to get you down to sync speed you would gain a stop or so of power that is intrinsically lost to HSS, but most of your gained power from lowering shutter speed would be used overcoming the darker scene and AF can be an issue.

We all know of the exposure triangle, aperture-shutterspeed-iso, most of us know the secondary flash exposure triangle, flash power and distance-aperture-iso. What many of us fail to take into account is when you go to HSS the shutter speed comes into the flash exposure triangle, wrecking it, and making a flash exposure square. At below sync speed the flash exposure is not impacted by the shutter speeds duration, all the flash is spent while the shutter is open, but in HSS the flash pulses, it pulses at the same rate at 1/8000 as at 1/300, obviously at 1/300 it gets 26 times more potential pulses than at 1/8000.

You have several options. Get the flash closer to the subject. Increase flash power, obviously that means another flash, but this will only give you one extra stop of light and is expensive. You can move location, that is find an area with less ambient, some open shade or a different time of day, not necessarily convenient. You can create your own shade, use a scrim, a sheet, an umbrella etc to put your subjects in shade, this is the most often used commercial technique, this has the added benefit of lowering the contrast across the subject so reducing the need for balancing flash, but again is not always convenient.


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## Skulker (Dec 9, 2013)

Marsu42 said:


> neuroanatomist said:
> 
> 
> > Bohns said:
> ...



I'm certainly struggling to get used to the flash settings.

But clearly it is possible to use flash at high ISO. Sometimes mine goes to 6400. And produces great reslts most of the time.

I'm not complaining as I suspect with my understanding of flash the camera is helping me.

I'm not one of those who will automatically assume that the camera is "crippled" or "broken" when it is restricted in some way. I start with the assumption that Canon know a lot more about making cameras than I do.


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## Marsu42 (Dec 9, 2013)

Skulker said:


> I start with the assumption that Canon know a lot more about making cameras than I do.



That's the spirit, I'll remember to nominate you for the "Canon compliance of the year" award  ... but you're correct, not every design decision is "crippling", but as it happens this one is different because ML has proven that auto iso with flash is no problem at all - you can use other iso settings manually, so there is really no reason why the camera shouldn't be able to select the iso according to the ambient light as usual and then let ettl decide the rest.


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## Bohns (Dec 9, 2013)

Thank you for all your answers, and for your welcome !

And thank you for this detailed answer, Privatedesign.



privatebydesign said:


> Even the 600EX-RT is very limited in HSS at 1/4,000. You have run into a hard limit. Changing iso would not help, if you lower iso the flash needs to output more power, which it can't do, if you lower the shutter speed you need to close the aperture (to maintain ambient) which will need the same flash power. If you raised iso then the flash would not have to work so hard, but again you'd have to close the aperture and that would take back the power you gained. If you used a ND filter to get you down to sync speed you would gain a stop or so of power that is intrinsically lost to HSS, but most of your gained power from lowering shutter speed would be used overcoming the darker scene and AF can be an issue.



I would have thought that reducing ISO would involve increasing exposure time, i.e. Decreasing shutterspeed to an output less than 1/1000s, potentially more favorable to HSS. But I don't understand why it would involve the flash needing more power, knowing I was quite close to my kids (about 3 meters). I am certainly not an expert, but I assume the distance is also of importance to determine the needed power when using E-TTL. Am I wrong ?

I did not want to close the aperture, but the bckground being only snow, it would have not been a real issue. I should have tried it. But my initial purpose was indeed to blur the background, which is the reason to use HSS primarily. So I remained at f2.8 or f4...


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## Chris Burch (Dec 9, 2013)

If your setup is causing the flash to fire at or near full power, it will take 2-3 seconds to recharge even with an external battery like the Propac (which I have and use regularly). You could either slow down your rate of shooting to accommodate or make the flash do less work (change to manual, slow the shutter, increase ISO, etc.).


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## Skulker (Dec 9, 2013)

Marsu42 said:


> Skulker said:
> 
> 
> > I start with the assumption that Canon know a lot more about making cameras than I do.
> ...



You mean as my 1Dx does, as I just pointed out. ;D

Thanks for nominating me for "Canon compliance of the year". Its really appreciated. Now where is that sarcastic emoticon when you need it. 

As someone who spent many years in product design and development I find it really irrational that people claim companies deliberately downgrade equipment as a matter of course. It may well happen but it is not something that I ever saw in the real world.


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## privatebydesign (Dec 9, 2013)

Bohns said:


> Thank you for all your answers, and for your welcome !
> 
> And thank you for this detailed answer, Privatedesign.
> 
> ...



Reducing iso would have increased shutter speed, but the power you gained from 1/4000 going to 1/1000, two stops, would have been lost to you by the iso going from 400 to 100, two stops. All the exposure factors remain constant. It isn't until you get below sync speed that you will start to get more effective flash power.

As a starting situation, turn camera on, put in Manual mode, set 100 iso, set sync speed, 1/200, then set your aperture where you need to get the ambient exposure you want (you lose selective dof control but that is the price you pay for optimising small flash in bright situations). Turn flash on in ETTL and dial in FEC to taste, my experience in snow is that the built in auto reduction/auto fill does a very good job. Take a picture. Look at the EXIF in review, if you don't like working in M mode go to AV and set one stop smaller aperture than the picture you just took, the camera will then do everything, however I find M easier and more consistent than AV and needing to use exposure compensation.

You were using 1/4000 @ f2.8 and 400 iso. I would have used 1/200 @ f6.2 and 100iso as a starting point for the same ambient but giving your flash the sync it needs to work effectively.


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## markojakatri (Dec 9, 2013)

I wrote another topic about this, but here is my observation:

I've find a cool way to use safety shift in 5D III. If you use Tv mode and safety shift (ISO), camera will use as high ISO as needed. It actually works identically w/wo flash.

The best thing is that you can use autoISO or set ISO manually. If you set ISO manually, consider your setting as a minimum ISO setting, camera will rise it anyways when needed. This is very nice feature in low light, where fill flash is needed. You can, for example, set high ISO to have f2-2.8, but when it gets darker, f1.2-1.8 are used and if that is not enough, ISO will be risen even more.


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## Skulker (Dec 9, 2013)

markojakatri said:


> I wrote another topic about this, but here is my observation:
> 
> I've find a cool way to use safety shift in 5D. If you use Tv mode and safety shift (ISO), camera will use as high ISO as needed. It actually works identically w/wo flash.
> 
> The best thing is that you can use autoISO or set ISO manually. If you set ISO manually, consider your setting as a minimum ISO setting, camera will rise it anyways when needed. This is very nice feature in low light, where fill flash is needed. You can, for example, set high ISO to have f2-2.8, but when it gets darker, f1.2-1.8 are used and if that is not enough, ISO will be risen even more.



That's interesting. I will see if I can use it.

Here's one I took earlier. ;D its ISO 1600. and 100% crop, NO PP in LR4, NO NR, NO sharpening etc etc.


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## markojakatri (Dec 9, 2013)

I meant in 5D III


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## Marsu42 (Dec 9, 2013)

markojakatri said:


> I've find a cool way to use safety shift in 5D III. If you use Tv mode and safety shift (ISO), camera will use as high ISO as needed. It actually works identically w/wo flash.



... but be careful, because reaching the highest iso setting you chose, it'll ignore your shutter speed preference and simply expose as long as required not matter if it's practical to handhold it any longer, that's why disable safety shift in tv mode. Better to get a more "flashy" picture than a blurry one with nice ambient.


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## markojakatri (Dec 9, 2013)

Marsu42 said:


> ... but be careful, because reaching the highest iso setting you chose, it'll ignore your shutter speed preference and simply expose as long as required not matter if it's practical to handhold it any longer, that's why disable safety shift in tv mode. Better to get a more "flashy" picture than a blurry one with nice ambient.



Yep, that's true. When it is dark enough, I change to manual and use bounced flash or two as main light(s).


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## neuroanatomist (Dec 9, 2013)

Skulker said:


> Marsu42 said:
> 
> 
> > Skulker said:
> ...



I guess your 1Dx is different from my 1D X. 

The issue at hand is when a Speedlite is attached, Canon cameras default to ISO 400 *when they are set to Auto ISO*. Are you saying your camera does something different?


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## Paul_B (Dec 10, 2013)

neuroanatomist said:


> ...
> The issue at hand is when a Speedlite is attached, Canon cameras default to ISO 400 *when they are set to Auto ISO*. Are you saying your camera does something different?



This is a problem for me as I take a lot of photos at parties and weddings where ambient light creates the atmosphere of the picture, but is volatile.
I need auto iso to work there between like 1600-6400 depending on the configuration of the lights at that second.
Either that or I have to fix my flash output and change this depending on my distance to the subject, but on a dancefloor this not possible to do well.

Reading this topic I have failed to understand why this fixed iso 400 is a reasonable thing as somebody said that the camera works just as fine with auto-iso plus flash running ML.


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## kang159 (Dec 10, 2013)

woah...poor OP must have no idea what's going on...


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## Marsu42 (Dec 10, 2013)

kang159 said:


> woah...poor OP must have no idea what's going on...



I hope the discussion doesn't sound too heated  ... but what he (and I when I got my dslr) had/has no idea what's going on about is that the camera suddenly locks to iso 400 if you enable the flash from Rebel to 1dx - imho it's just like the previous poster stated: auto iso with flash can make sense, it works with ML, and it's difficult to understand why it doesn't by default. Maybe a feature reserved for 5d4, 6d2, 80d just like ec in m mode :-> ?


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## Skulker (Dec 10, 2013)

neuroanatomist said:


> Skulker said:
> 
> 
> > Marsu42 said:
> ...



I'm not sure if mine is diferent to yours? Send me yours so I can carry out some tests if you like. 

I use a 580ex11 on camera or on an extension lead., and most of the time it defaults to ISO400. But sometimes it goes to ISO6400. The manual indicates that it will go to ISO1600. I freely admit I'm out of my depth with flash. I hardly ever use it and find it a bit of a black art. Why the owl shot I put in this tread was at ISO1600 and the one next to it was at ISO400 I have no idea. There is a color cast to the owl so maybe the flash was overheating?


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