Adjusting ambient light levels when using flash

[Mark von Kanel]

HA! i knew this thread would explode with you 100% Colin but could face all that typing! Keep reading Adrien, once you get used to its fun

[William W]

. . . a Samsung NX 11 using a hotshoe flash on TTL mode. . . my question is this....If I'm in aperture priority mode . . . can I simply reduce the EV reading in the viewfinder to reduce ambient light as I assume that, for any given aperture, the shutter speed will increase?

Assuming “reduce the EV reading” means “use Exposure Compensation” – the answer is: Yes – unless the Samsung is a very unusual camera.

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The question is – why didn’t you just try it and see for yourself?

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The camera in question has a Maximum Flash Speed of < 1/180s and it might do either of three options if the Shutter Speed is increased to or beyond that Speed:
1. It may not allow the shot
2. It may not allow the increase in shutter speed and allow the shot
3. It may allow the shot and record a Flash Sync Bar (vignette)


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As the answer to this specific question the follow statement is INCORRECT:

“Aperture controls both ambient and flash [exposure], in that both will be affected when changing aperture: in both cases the amount of light that can pass to the sensor in a given time is modified.”

The statement is incorrect because: with the Flash in TTL Metering Mode, the Flash Intensity will be automatically adjusted to suit the Aperture which is chosen.

WW

[Mike Buckley]

keeping in mind that Nikon appy EC to flash as well, so if you dial in -EC you may well need to dial in +FEC to compensate

Another way to say that: On a Nikon system (I don't know about any other system), the flash exposure compensation is automatically added to the camera exposure compensation. As in Colin's example, if your camera exposure compensation is set to -1/2 EV, you will need to set your flash exposure compensation to +1/2 EV if you want a total exposure compensation of 0 EV.

[Colin Southern]

The statement is incorrect because: with the Flash in TTL Metering Mode, the Flash Intensity will be automatically adjusted to suit the Aperture which is chosen.

Possibly worth also adding "assuming that the flash has sufficient power to do so" (I say that because it seems to be quite a common occurrence where people are stopped down too far and can't get enough power out of their flashes) (eg group shot - against setting sun - F16 - and a single flash!).

[Colin Southern]

Another way to say that: On a Nikon system (I don't know about any other system), the flash exposure compensation is automatically added to the camera exposure compensation. As in Colin's example, if your camera exposure compensation is set to -1/2 EV, you will need to set your flash exposure compensation to +1/2 EV if you want a total exposure compensation of 0 EV.

I was surprised to read that on the new D4 they've changed this, and it now works the same as the Canon system where the two light zones are independent.

[northlondon43]

Hi William... Yes of course I'll have a go but wanted to see what people's opinions were... Theory and practice.
On another note I'm always amused how what seems a simple question to me blooms into such a long thread which goes this way and that... way over my head most times.
Perhaps a beginners forum should be created because frankly I'm getting more and more reluctant to post questions on here.

[William W]

Possibly worth also adding "assuming that the flash has sufficient power to do so"

Thank you: very worthwhile adding that.

WW

[William W]

Hi William... Yes of course I'll have a go but wanted to see what people's opinions were... Theory and practice.

That’s an interesting comment.
Your original question is neither really open to “Opinion” nor to “Theory and Practice” it is a simple technical question which has a very simple technical answer: “Yes” (unless the camera is very strange and does not follow convention).


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On another note I'm always amused how what seems a simple question to me blooms into such a long thread which goes this way and that... way over my head most times.

A forum is a place to discuss.

By comparison to many other discussion places, CiC Forums have ALWAYS engendered a respectful and engaging and non-threatening discussion: my advice is, if something is not understood ask for more detail or an explanation about it – there is much to learn.

On the other hand IF your original question has not been answered and your thread has gone wayward – (that’s just human nature) then jump back in and retrieve it – it is not all that difficult to ask “come on guys and girls – please give me simple ‘yes’ or ‘no’ answer with a little explanation - I think the thread has gone off topic”


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Perhaps a beginners forum should be created because frankly I'm getting more and more reluctant to post questions on here.

I disagree.

The formula and membership at CiC is very considerate of all levels of skill and experience.

No ‘beginner’ should feel threatened to post in any of the forum subheadings nor should they feel any question is too basic – this is one of the great strengths of CIC – the SIMPLICITY.

Worthwhile Discussion is a two way commitment – and that is not having an expectation that once one posts a question the required answers will simply flow in at ones beck and call.

It would be a shame and also your loss, for your reluctance to post questions to overcome and direct you.

You should think long and hard on that point.

CiC is a very valuable resource, but as with most valuable things in life - you will only reap what you sow .

WW

[Geoff F]

Don't worry, Adrian, if an answer isn't totally clear to you just ask again for greater clarification and members will try to explain things in a different way. It is all too easy to talk in technical terms assuming that everyone else is at the same level.

[Colin Southern]

Adrian,

If you haven't found the answer to your question then yes - please do keep asking.

In threads like this I won't say it's "drifted off topic" per se, but as is often the case, errors and misconceptions can creep in to some replies necessitating that we go into some of these a bit (or a lot) deeper; those contributions are not so much for your benefit as they are for some of the others so that they can round out their knowledge on the topic. Flash is probably the best example of this; it's straight-forward enough in theory, but still a lot of "gotchas" with regards to how they work / don't work ... and their real-world limitations.

So please don't be "scared off" - instead, just take from it all that you need for now, and don't worry about the rest. In time you'll be able to put more and more of it to good use.

[John Morton]

Perhaps a beginners forum should be created because frankly I'm getting more and more reluctant to post questions on here.

I'll assume that comment is tongue-in-cheek, Adrian, and meant in a good humored way because in my experience people here in no way mean to intimidate those who post questions. Quite the opposite - there are very many knowledgeable people here that thoroughly enjoy photography and are happy to help others who are just starting out.

Please remember, though, that once a question is posted the replies are addressed to everyone (being as they are public). So often, someone responding will include a wider range of information than may have been requested, since others who are interested in the topic of discussion will no doubt have slightly different needs than the original poster.

I'm following this thread with interest even though the most pressing question for me is unlikely to be answered: which buttons do I push to do what? Well, I'll have to figure that out for myself, having now been exposed to a thoroughly wide survey of what I should be trying to do in the first place...

[Mike Buckley]

which buttons do I push to do what?

My use of a speedlight is not as intuitive or as natural and easy-going as my use of the rest of my camera system. There are so many details about using a speedlight that I haven't come close to remembering most of them. So, I created a Quick Reference Guide that tells me all that stuff and I keep it with my camera at all times. It literally tells me what buttons to push to accomplish whatever I want to accomplish.

[Geoff F]

My use of a speedlight is not as intuitive or as natural and easy-going as my use of the rest of my camera system. There are so many details about using a speedlight that I haven't come close to remembering most of them. So, I created a Quick Reference Guide that tells me all that stuff and I keep it with my camera at all times. It literally tells me what buttons to push to accomplish whatever I want to accomplish.

Yes, sometimes I push the wrong button and get lost; so I have to turn everything off then start again.

[Dusty]

With regards to the notorious SAAF - Shutter Ambient Aperture Flash

... this is something we often hear, but what we DON'T often hear is the other part of the explanation; Technically it's only about a quarter right in that adjusting the shutterspeed doesn't have any effect on the flash portion of the exposure until you get into high-speed sync mode - after that the flash is in essence a constant light source and if affected by shutterspeed. Adjusting the aperture affects the flash - BUT - it also affects the ambient light too (just try it in manual mode if you don't believe me ). What Syl (and others) are assuming when they use the SAAF saying is that you're using one of the automatic exposure modes, and you're below X-Sync speed. So it's not so much a case of "aperture controlling flash" as it is "aperture controlling both flash and ambient, but the camera will compensate for both by increasing/decreasing the shutterspeed and increasing/decreasing the flash output (in Av mode for that example)". So if you're using an automatic exposure mode - and not using HSS mode (which is a very typical situation) - then yes, the SAAF acronym works. If you're using a manual exposure mode or HSS mode then it doesn't.

Hope this helps

In HSS mode the SAAF is still the same, the Aperture works the flash and the shutter speed is above the sync speed of the camera , you set the shutter speed to whatever the subject needs, as in the image below. The three dancers to the right of the image where moving at way above my sync speed of 250 so I went to HSS and moved my shutter speed to the approx and took the shot. I don't think Syl is saying aperture is controlling both shutter speed and ambient exposure it doesn't with me.

[Colin Southern]

With regards to the notorious SAAF - Shutter Ambient Aperture Flash



In HSS mode the SAAF is still the same, the Aperture works the flash and the shutter speed is above the sync speed of the camera , you set the shutter speed to whatever the subject needs, as in the image below. The three dancers to the right of the image where moving at way above my sync speed of 250 so I went to HSS and moved my shutter speed to the approx and took the shot. I don't think Syl is saying aperture is controlling both shutter speed and ambient exposure it doesn't with me.

Syl actually explains it very well -- the problem is that people only ever quote the little mnemonic without the supporting context, and then try to apply it out of context.

Personally, I don't really like the mnemonic because people don't understand the whole story; just like the sunny 16 rule when they neglect to mention that it's only for front-lit subjects and for 2 hours after sunrise and no more than 2 hours before sunset (you never hear that bit).

With regards to SAAF and HSS; once you hit HSS the shutterspeed affects both the ambient AND the flash light, as does the aperture. Only changing the flash power or the flash to subject distance varies the flash to ambient ratio, so SAAF in that context doesn't "hold up".

Personally, I have HSS switched on 100% of the time so the camera can use it if it needs it, but doesn't use it if it doesn't need it. Normally I'll just shoot whatever aperture and shutterspeed I want - the SAAF thing really only kicks in when the aperture is too narrow and the flashes don't have enough power.

[revi]

With regards to the notorious SAAF - Shutter Ambient Aperture Flash



In HSS mode the SAAF is still the same, the Aperture works the flash and the shutter speed is above the sync speed of the camera , you set the shutter speed to whatever the subject needs, as in the image below. The three dancers to the right of the image where moving at way above my sync speed of 250 so I went to HSS and moved my shutter speed to the approx and took the shot. I don't think Syl is saying aperture is controlling both shutter speed and ambient exposure it doesn't with me.

(...)

I see what you wanted to do, but:
it looks like your flash was the main light source for the dancers. I was always told that the duration of a flash (in 'normal' mode) was short enough to freeze all movement (in the order of 1/2000 s?);
So why use HSS here (losing a lot of power), when the flash duration seems already short enough?

[Dusty]

revi, try taking a image when people are moving so fast and when it's dark and keeping the bg normal. Power wise yes it uses a lot of power but it is only a short duration. When you use your flash with the camera it is usually in first curtain mode and if you took a image when they where moving the flash fires at the opening of the first shutter and if the subject is still moving you get the subjects features still getting taken and if you use second curtain with a slow shutter speed you get the trail behind them.

[William W]

With regards to SAAF and HSS; once you hit HSS the shutterspeed affects both the ambient AND the flash light, as does the aperture. Only changing the flash power or the flash to subject distance varies the flash to ambient ratio, so SAAF in that context doesn't "hold up".

+1

Very important and often, very often, not understood: especially when using Flash as Fill and HSS.

I don't like the acronym either, for this exact same reason.

WW

[Dusty]

For all of you who doubt Syl Arena and his SAAF read his book 'Speedliter's Handbook' and also Neil van Niekerk three books on 'On-Camera Flash, Off-Camera Flash and Direction & Quality of Light', they are worth reading if you want to understand using Flash better.

[Donald]

For all of you who doubt Syl Arena and his SAAF read his book 'Speedliter's Handbook'

I didn't read Colin and Bill as doubting what Arena says. Indeed he says it himself in the book (which I think is great). Without going through it (even though it's sitting beside me here on the desk), he makes the point that SAAF is not applicable in a HSS situation.

So, it's not an either/or, or good/bad, situation. I think Syl Arena is right. And Colin and Bill are right.