Adjusting ambient light levels when using flash

[northlondon43]

Good morning everyone (at least it is where I am) :-)

My set up is a Samsung NX 11 using a hotshoe flash on TTL mode.

Most articles on flash photography I've read recommend adjusting shutter speed to adjust ambient light levels as doing so means that the flash output doesnt need to change. Fine, I think I understand the theory behind that and have successfully tried it a couple of times in camera manual mode (flash on TTL).

However my question is this....If I'm in aperture priority mode (and I shoot a lot in this 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?

Cheers

Adrian

[RockNGoalStar]

The way to control ambient light with the use of a flash is with the aperture setting. Decrease the size of the aperture (higher f-number) to reduce the ambient light and vice versa.

If I'm indoors, at a party for instance, where it isn't that bright I would try something like f/16 @ 1/60 sec as a starting point and take it from there. Also, I very rarely point the flash directly at my subject, preferring instead to bounce it off the ceiling or nearby wall if I can.

I am not wholly proficient in my knowledge and use of the flash (yet) but I find with these very simple settings / techniques I have got some pretty pleasing results

[Mark von Kanel]

Adrian, Using flash is a little more complicated than that but once you,ve got the fundamentals sorted youll find it becomes second nature. i strongly recommend you get yourself over to strobist.com and read through the strobist 101 & 102 courses on there.

Altering the EV in the camera will effect the ambient light, whilst altering the flash EV will alter the flash output/subject illumination.

A thing to remember is that using your highest shutter sync speed will allow you to use a larger aperture and so reduce the amount of flash power required per shot and this will reduce recycle time and increase your battery life. It took me ages to get my head round that one!

Im not sure about the use of A mode with flash is a good one as this may push you above your max sync speed, which with the samsung is less than 1/180 and give banding on your images, i would use manual or shutter priority

Im still learning myself but im fairly certain the information ive put up there is correct and if not someone will be arround shortly to correct me!

[Andrew76]

Good morning everyone (at least it is where I am) :-)
However my question is this....If I'm in aperture priority mode (and I shoot a lot in this 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?

Cheers

Adrian

Hi Adrian, what you've said, is correct, and was confirmed by Mark - this works even in AV mode. However - all EV does, is adjust shutter speed, so if you're going to the extra effort, may I ask why you just wouldn't shoot in M? You're already setting the aperture to what you'd like, and then you're taking the extra step to plug in an EV, to me it would just make sense to start off in M.

Tommy, sorry, I'm going to have to disagree with you on that one. Aperture setting controls flash light, not ambient - even though Colin hates when I say that; he'll especially hate when I give you this handy acronym to remember!

SAAF - Shutter Ambient Aperture Flash - hope that helps!

[russellsnr]

Hi,Have a look at these, http://www.sekonic.com/Classroom/Web...dWebinars.aspx I no they are sponsored by Sekonic but there is loads of good advice IMO on shooting in and outdoors, start at Control the Light and Improve Your Photography:
Part I — Portraiture Using Available Light
3rd from the bottom and just work up the way.
Russ

[Donald]

SAAF - Shutter Ambient Aperture Flash - hope that helps!

Another Syl Arena disciple.

It might be open to challenge and criticism as a concept, but it certainly keeps me aligned in the right direction on the few occasions that I use flash. (Note to self - Must use it more often)

[Andrew76]

Another Syl Arena disciple.

It's true. The man knows what he is doing!

[revi]

I'll have to disagree with both Tommy and Andrew:
Aperture controls both ambient and flash, 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.
Exposure time, otoh, only affects ambient, as long as the flash duration is shorter than the exposure time (and flash duration of commercial flashes is < 1ms, or 1/1000s, with sync usually around 1/125s - 1/250s).
Just keep in mind that that is for 'normal' flash use, HSS could be different (no experience with it).

So that gives you four settings to play with to balance flash and ambient:
- ISO (ambient and flash intensity)
- aperture (idem)
- exposure time (only ambient intensity)
- flash output (only flash intensity)

So, in practice, when in Av mode, EV correction and flash EV correction let you play with both more or less independently, and you can use ISO and aperture to set a kind of base exposure time (e.g. to minimise camera shake)

[Colin Southern]

Hi Adrian,

Lots of confusing information circulating when it comes to flashes, unfortunately. I don't know anything about Samsung cameras or flashes, but here's how it works in the Canon world (and I believe Nikon is much the same).

Think of flash photography as working 2 separate light zones - the ambient zone and the flash zone. The ambient zone exposure is affected by the exposure mode you select - which is inturn dependent on the situation you're in:

In Aperture Priority mode, the camera will adjust the shutterspeed to get a normal exposure for the combination of ISO and aperture you have selected - but - there are a couple of "gotchas" with this; if you're shooting with low light levels (eh at night or inside where light levels are generally quite low) then the camera may well decrease the shutterspeed to a point where camera shake becomes a problem. In this situation increasing the ISO or opening up the aperture are your only options in terms of ambient light. If the light is too bright then the shutterspeed may increase to the point where you hit your X-Sync speed (the highest shutterspeed you can take a shot at with a flash that's not using high-speed sync mode) (don't know if your flash has HSS mode). If the scene requires a higher shutterspeed than this then the camera will probably still take the shot, but it'll be over-exposed. In this situation all you can do is decrease the ISO or stop-down the aperture - or use a neutral density filter to cut back the ambient light.

In Shutter Priority mode you get to choose the shutterspeed (so you can control camera shake), but you'll lose control of your aperture to a degree (I say "to a degree" because manually adjusting ISO will still give you indirect control) - and generally - we want control over our apertures because they determine our depth of field (shutterspeed is less critical, which is why most folks use aperture priority mode).

In Manual Exposure Mode you get to choose all three variables (aperture, shutterspeed, and ISO), but you also assume full responsibility for the results.

There are also other modes (like "P" mode) that behave slightly different again, but I won't go into them.

Regardless of mode, the flash is pretty much the same -- it'll try to obtain a standard exposure of the flash zone (unless you over-ride it with flash exposure compensation).

So putting all of that into a real-world situation ...

If you're shooting in a dark area - and you really don't care if the ambient zone is under-exposed or not - then you'll probably be better off using Manual exposure control so that you don't end up with a ridiculously low shutterspeed (Av mode) or inappropriate aperture (Tv mode).

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

[Andrew76]

Makes sense to me - thanks for the clarification.

I just always assumed SAAF was the 'simple' way to explain it. In fact, I brought it up because Adrian mentioned he was shooting in an automatic modes. But for Manual I see how it is not the case.

[Colin Southern]

Hi Remco,

Right on the money! Just a couple of "expansions" ...

Aperture controls both ambient and flash, 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.

Quite correct. Just keep in mind that the saying is for AUTOMATIC EXPOSURE modes - and thus the "in a given time" bit goes "out the window" because the camera will compensate by altering the shutterspeed.

Exposure time, otoh, only affects ambient, as long as the flash duration is shorter than the exposure time (and flash duration of commercial flashes is < 1ms, or 1/1000s, with sync usually around 1/125s - 1/250s).
Just keep in mind that that is for 'normal' flash use, HSS could be different (no experience with it).

HSS is essentially a constant light source. Once you're in HSS territory it's essentially a straight "drag race" between ambient and flash (the stronger of the two will have the most effect on the part of the image illuminated by the flash light).

So, in practice, when in Av mode, EV correction and flash EV correction let you play with both more or less independently, and you can use ISO and aperture to set a kind of base exposure time (e.g. to minimise camera shake)

You can play with EC and FEC - often it's just easier to use manual exposure with FEC unless light levels are continuously changing though (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) (apparently they've changed this to work the same as Canon in the D4).

[Colin Southern]

Makes sense to me - thanks for the clarification.

I just always assumed SAAF was the 'simple' way to explain it. In fact, I brought it up because Adrian mentioned he was shooting in an automatic modes. But for Manual I see how it is not the case.

Hi Andrew,

I think it's a bit like the old "Sunny 16" rule - people often quote the rule, but they never mention the qualifying part of it ("only for a front-lit subject, and more than 2 hours after sunrise, but more than 2 hours before sunset).

The reason I mention it is that more and more folks are now using HSS mode -- some of my outdoor portraits are up in the 1/2000th and 1/4000th area - and the ONLY thing changing aperture accomplishes is a different DoF, because the ratio of the lighting (ambient to flash) remains exactly the same (assuming the flashe(s) have enough power to still illuminate the scene the required amount). In that situation, the ONLY thing that affects the flash to ambient ratio is changing the effective flash output (ie electronically or changing the distance) (depending on flash mode).

[Geoff F]

Adrian, when I first moved from my old film camera flash to a modern 'self thinking' flash I was never happy with the results. I am using Canon equipment so some things may be slightly different.

Eventually I started using full manual camera settings, as Andrew advised. Originally for insect photography then I tried the same technique on most flash shots. Suddenly I was getting much better results.

With the old style fixed output flash light level you had to find ways of controlling the output. Shooting with Tv (shutter priority), putting diffusers over the flash head or shooting at the ceiling were all ways around the problem. Using aperture priority often gives shutter speeds which are far too slow for practical use.

However, with modern flashes you can easily control the flash output. This gives you the opportunity to manually set your camera to suit the actual scene, without worrying too much about the ambient light level. Subject to a few camera limitations as previously mentioned.

This means that I now don't have to shoot at 1/60 which was often too slow for the scene action, or gave me camera shake. And I don't work with the lens fully open either.

So if the scene layout would have required, say for example, 1/200 F8 in good lighting that is what I use; and let the flash output find it's own level.

The downside of manual camera settings is that you have to do your exposure compensation by varying the flash output compensation which takes a little bit of experimentation.

Sometimes, I do still shoot at the ceiling if I am able to take a number of shots in order to work out the best settings. But for quick action work, where I only have one chance, I find that too often I angle my flash at the wrong piece of ceiling and the main flash has fallen behind the subject.

Or, as frequently occurs, the flash output level has been automatically reduced which results in a dark scene. The camera saw it as a dark scene.

Fixed camera controls with variable flash output pointed directly towards the subject certainly works the best for me under most circumstances.

[Colin Southern]

Another Syl Arena disciple.

It might be open to challenge and criticism as a concept, but it certainly keeps me aligned in the right direction on the few occasions that I use flash. (Note to self - Must use it more often)

Syl is a good man - so just to clarify, from Syl's Excellent book ...



but wait, there's more ...



Point being that he makes the distinction of there being "no free lunch" in that if you adjust aperture to adjust flash, you need to adjust shutterspeed to compensate (unless the camera does it for you).

If anyone want to buy the book by the way, you can find it here or here (kindle edition, print edition).

[Colin Southern]

Adrian, when I first moved from my old film camera flash to a modern 'self thinking' flash I was never happy with the results. I am using Canon equipment so some things may be slightly different.

Eventually I started using full manual camera settings, as Andrew advised. Originally for insect photography then I tried the same technique on most flash shots. Suddenly I was getting much better results.

Hi Geoff,

Generally speaking, I find it easier to use manual exposure when the automatic modes give me an undesirable potential outcome (ev Av mode at night) - at normal light levels though I usually find it easier to just let the automation "do it's thing" -- on later cameras it got to the stage where it's pretty darn hard to fool it (especially where light levels are changing all over the place)

[Geoff F]

For me, the auto settings tend to give me 1/60 at fully open aperture; or a fixed shutter speed (Tv) still with a full open aperture. And often with too bright a flash. The only way I can control both shutter and aperture is with manual camera settings.

Av can work OK when on a tripod with a static subject.

Working with 7D, but usually F4 lenses. Faster glass may work better.

[northlondon43]

Firstly I'd like to thank everyone,as usual on here, for giving their thoughts. As ever what I thought was a fairly simple question has provided many, to me, complicated answers. I promise to read/think about all your comments and suggestions. Sometimes though I must admit that I feel totally overwhelmed by the what appears to be very technical, sometimes conflicting?, advice.....my problem though...I don't do this professionally...:-P

[Geoff F]

Photography, like many things in life, Adrian, is all about experimentation to see what works best for you.

[Andrew76]

but wait, there's more ...

See, my wife was right. I only hear what I want to hear.

[Colin Southern]

For me, the auto settings tend to give me 1/60 at fully open aperture; or a fixed shutter speed (Tv) still with a full open aperture. And often with too bright a flash. The only way I can control both shutter and aperture is with manual camera settings.

Av can work OK when on a tripod with a static subject.

Working with 7D, but usually F4 lenses. Faster glass may work better.

Hi Geoff,

It won't do that (1/60th) in Av mode - unless you're using Auto ISO. It will do it in some auto modes though (1/60th is the magical "no camera shake " figure manufacturers have chosen for a typical focal length).

I'm not saying "manual everything" is bad - it's just a PITA if you're shooting in changing conditions