Brain dead flash question

[KIPAX]

If I want to use eg f8 indoors with the max 250 shutter speed I can get... Why do i need to up the iso so much when the flash is supposed to light up the subject

Say AV mode.. F8 ..i cant get the shutter speed up unless I up the iso.


I really hate flash.. dont understand it no matter what i read.... wheres the idiot guide?

 

[hepburn]

Use manual mode instead. Try iso100, f11 @ 250. Take a test shot, then adjust from there. This is what I start with when shooting with studio lights.

 

[poacher]

This may help, I need the complete idiots guide, I have problems with flash as welll.

http://photonotes.org/articles/eos-flash/

 

[KIPAX]

is that flash in ettl and camera on manual and adjust means start upping the iso...

OK and that seems to work. (TA!)... but will only work for the one time one subject yes.. ie person in middle of room (or wahetevr)...adjust until happy and thats it... but suppose taking shots around a room at various distances?

 

[KIPAX]

thanks poacher that helps a bit.. although i think thats the only time I put this in P mode... not gonna be doing that again

Looks like manual is best to settings I would like... then the flash on e-ttl will do the rest to get right exposure.. but if it struggles then up the iso until its happy... oh and ignore the exposure meter that says its well out.

sound right?

 

[photon]

This seems to be the most applicable section:
http://photonotes.org/articles/eos-flash/#faq10

P (program) mode keeps the shutter speed between 1/60 sec and the maximum flash sync speed your camera can handle. It does this so that you shouldn’t need a tripod, even if light levels are low. It then tries to illuminate the foreground using flash.

Av (aperture priority) and Tv (shutter speed priority) modes set the shutter speed or aperture to expose for the existing light conditions correctly. They then fill in the foreground using flash. If light levels are low you will need a tripod to avoid blur.

M (manual exposure) mode lets you set both aperture and shutter speed to be whatever you want. The camera then automatically controls the illumination of the foreground subject using flash.

 

[KIPAX]

Photon.. you got it all in one short note.. thats what i had summised BTW but thats it simple and clear there in one small post... nice one

 

[KIPAX]

I can't believe I am asking this next one.. but needs must

Does it know if you have redirected the flash to say bounce off a ceiling.. does it know its not ppointing forward and compensate or do you ahve to comepnsate yourself

 

[photon]

With my Pentax system, it does know if you are bouncing, but does not compensate (grrrr). However, the "A" setting, using the flash's own sensor, is accurate and often recommended, as it's not affected by highly reflective small objects causing the flash in TTL mode to quench its output.

====

Edit:

Well, having had a long play with my 540 flash in several camera modes I don't ever usually go near, the "A" setting is good for the flash in the "normal" straight ahead position, but needs perhaps a stop of compensation when bounced (set the flash to f11 when f8 is set on the camera). The "A" setting allows for up to 1600 ISO whereas the P-TTL is designed for up to 800 ISO and will overexpose high ISO shots.

There's a Night Portrait auto setting on the camera which meters the ambient light and opens the aperture as wide as possible and drops the shutter speed (tripod warning!), but is stuck on auto white balance and won't allow the background to be underexposed by 2 - 3 stops, so I prefer the Manual camera setting. If the background is closer to a correct exposure, any shadows from the ambient lighting will be more visible (which could be a good thing), and the shutter speed will be slower than with 2 - 3 stops underexposure.

With the P-TTL setting, there's a severe risk of underexposure with the flash head straight ahead and any reflective items in the scene. This seems to be completely solved with any of the bounce positions (maybe the flash switches to ordinary TTL?).

Contrary to what I wrote earlier, above, there is auto compensation for bounced flash. I'm used to adding a stop when using a bounce card and we have to be aware of the restrictions of the equipment. Bouncing can reduce the effective range by nearly a half due to the extra distance the light has to travel, and there'll be a further reduction in range due to the absorption of the ceiling or wall and any colour correcting filter used on the flash.

 

[pxl8]

If I want to use eg f8 indoors with the max 250 shutter speed I can get... Why do i need to up the iso so much when the flash is supposed to light up the subject

Say AV mode.. F8 ..i cant get the shutter speed up unless I up the iso.


I really hate flash.. dont understand it no matter what i read.... wheres the idiot guide?

The camera's meter only reads the ambient light, not the flash. This might sound daft but it's actually very sensible because you can balance the flash and ambient light to have full control over the mix of the two. Meter for how much of the ambient light you want and then leave the flash in ETTL mode and it will light the subject correctly. If you leave the camera in Av mode then this is the default behaviour. Stick it in manual and then you can more control over the ambient light level that is recorded. In a dark room shooting at 1/250s f/8, ISO100 then you probably won't get any of it. Adjust the settings until you've got about 1 stop under is normally a good place to start if you want some ambient light.

Does it know if you have redirected the flash to say bounce off a ceiling.. does it know its not ppointing forward and compensate or do you ahve to comepnsate yourself

ETTL works by firing a low powered pre-flash before the main burst. The amount of light returned from this burst is then measured to calculate how much is needed for the "actual" burst which is fired shortly after. It happens so quickly it appears as only one burst to most people but if you set the flash to 2nd curtain and have a long shutter speed you can see both bursts.

So it doesn't matter if you're bouncing or using direct, the metering is done from the light of the 1st burst getting back through the lens.

One important thing to bear in mind is that flash metering is very much connected to subject distance, the first thing that returns light through the lens is what the metering will be based on. If the light is hitting something close by then it will determine the flash exposure and that might not be the subject. Imagine a group sat around a table at a dinner, the white tablecloth will return a lot of the light and fool the metering so you'd need to dial in from +FEC to compensate.

 

[KIPAX]

Cheers pxl8 .. starting to get the idea now... trouble with articles and help files and instructions .. you get bogged down with loads of useless information (at time of reading) or terminology yer not used to... simplified is best... idiot guides rule

 

[tdodd]

Kipax, I haven't seen a direct answer to your original post. What size room are you shooting in and what is the distance to your subject? Also, are you bouncing or otherwise diffusing/modifying your flash output? The guide number for the flash is critical in letting you know how much distance the flash can cover at any given aperture and ISO.

e.g. The Canon 580EX has a guide number of 58 meters when zoomed in to the 105mm focal length setting. That's the range it would have if you shot at 100 ISO with an f/1.0 lens. If you shoot at 100 ISO and f/8 then your maximum subject distance will be 58/8 = 7.25m. If you shoot with a wider angle lens than 105mm then the flash light has to spread wider and gets weakened as a result. I don't know how by how much the range is affected at wider zoom settings.

If you put a diffuser on your flash gun or bounce the flash then your range will be reduced further, probably by at least 1 stop and maybe 2 or even more. A 2 stop loss reduces your range by half.

The popup flash on Canon cameras has a guide number of 13m, so at 100 ISO and f/8 it would have a range of 13/8 = 1.6 m.

If you increase your ISO by 2 stops then you double your range with the flash. This is all straightforward maths based on the inverse square law. If you double your distance you need 4X the power or 4X the sensitivity, which is 2 stops.

Taking all the above into account, it should be reasonably simple to figure out the maximum distance your flash will cover for any given ISO, aperture and method of deployment. Working backwards, you can figure out what ISO you will need to shoot a subject at a particular distance for any given aperture.

 

[photon]

As mentioned in #6 and #10, in Av mode Canons meter for the ambient light.

I'm in a dimly-lit room (but my local pub is darker) requiring 1/8 second at f/8 with 3200 ISO. This would need five stops more sensitivity for a 1/250 shutter speed at f/8. Turning on more lights brightens the scene by a couple of stops, but we're still a long way off it being bright enough for 1/250 in a non-photographic lighting situation.

With the flash switched on, in Av mode my camera tailors the shutter speed to the focal length, to maximise the contribution of ambient light for minimal camera shake. This can be avoided in other modes, where higher or lower shutter speeds may be desired.

If we use a flash Guide Number of 48 as an example, then the max range will be 6m at f/8 with 100 ISO. Bouncing at 60 degrees doubles the light path, reducing the horizontal range to 3m, which is then reduced to about 2m due to absorption by the ceiling or wall. Bump the ISO up to 400 to double the range to 4m.

 

[KIPAX]

gulp!

TBH I have saved tdodds post to my PC so i cant take it in when I have a moment and experiment ...THANKS tdodd BTW

I am snowed under ATM but will be looking at using M and 250 shutter as I cant seem to ever get anything below 200.

 

[tdodd]

I don't know whether this will help or confuse, but here is a table of flash coverage distances from the Canon 40D manual for the builtin flash. As I said, the guide number for this flash unit is 13m. When you use the 18-55 lens at its widest aperture - f/3.5 - and at 100 ISO your maximum effective flash distance is 13/3.5 = 3.7m. The flash power can also be reduced so anything within 1m-3.7m should be correctly exposed. If you check the figures for higher ISOs, at 400 ISO (2 stops greater than 100 ISO) the effective maximum flash distance is doubled to 7.4m. If you increase the ISO another 2 stops, to 1600 ISO you will see the maximum effective distance is doubled again to 14.9 (well, 14.8 is the exact double but there is rounding of fractions that means the maths looks a tad off, even though it isn't).

You will notice that at the tele end of the zoom the maximum aperture is just f/5.6, so the maximum effective distance is even less, at 13/5.6 = 2.3m at 100 ISO.

If you wanted to shoot with the builtin flash at f/8 then at 100 ISO your maximum effective distance would be 13/8 = 1.625m. At 400 ISO it would be 3.25m and at 1600 ISO it would be 6.5m.

 

[KIPAX]

Luverly... I did have the 420ex but since starting the thread I now have a 550ex + quantum1+ battery pack

 

[silverJON]

I am using a Metz 48 AF-1 with my Pentax K100D. I'm aware of how flash coverage and metering works.

As far as I can tell, if the camera is set to program mode with no exposure compensation and the flash is in normal PTTL metering mode with no flash compensation, if the flash is powerful enough to correctly expose the subject, it will, right?

Regardless of flash orientation. It shines until it's bright enough, right?

Why is it, then, that the flash will go through the full procedure of preflash-metering then limiting flash output appropriately but still underexpose the picture, and KNOW that it's underexposed the picture (the flash has a little illuminator to tell you)? What stopped it getting it right in the first place?

Why does it make you set the flash compensation up a stop or so to create perfectly-exposed shots that the flash is then happy with?

 

[tdodd]

As far as the Canon system is concerned, which is all that I have experience with, flash metering is no more intelligent than regular ambient light metering. If you point the flash at a predominantly pale/white object (wedding dress, white car etc.) the flash meter will still want to deliver you an 18% grey image so you will have to dial in some +ve FEC to keep your whites looking bright. That is one reason why you (should) have an FEC control. Equally, if you point the flash at a predominantly dark subject it will again attempt to render an 18% grey image, give or take. You need to use FEC to inform the flash that the subject you are aiming at is a dark object and not simply a poorly lit mid-toned object.

To further complicate things, if there is something lurking in the scene with exceptional reflectivity - glass in a picture frame, a window, a mirror, a white wall behind your subject - then the flash can be tricked into underexposing. The Canon flash metering system is generally very protective of highlights and if it sees a bright reflection coming back from the pre-flash it dials the flash right back, whether the reflection is from your "subject" or some other part of the scene. It is up to you to read the scene before you and set up the flash with FEC, just as you would EC for a picture without flash. Use of EC and FEC is quite independent but not mututally exclusive. You can use EC to adjust your ambient exposure up or down to taste and separately adjust your FEC to alter the flash. In this way you can make the background brighter or darker than your flash illuminated subject, as you see fit.

Another little quirk to be aware of, at least with Canon - if you point the flash head directly forward towards your subject (not tilted at all) the camera will use distance data from the focus of the lens within its calculations for the strength of flash required. In other words the distance data will limit the maximum flash output to somethig suitable for that distance, even if you have a black cat in a coal cellar. There is no point chucking out enough light to illuminate a subject at 20' if the measured distance to your subject is only 10'. This is great if you leave the flash bare. But as soon as you add some sort of diffuser/modifier (e.g. Omnibounce or Lightsphere) then they sap the flash of power. The flash does not know whether or not you have fitted a diffuser, so it bases its calculations on a bare flash. If you have a diffuser mounted then your flash output will be too weak. Of course, if you tilt the flash head in order to bounce then all bets on distance are off and the flash works purely on reflected light metering, which means a diffuser is fine.

Oh, and another thing with the Canon system - the Canon engineers have decided that at certain (lower) levels of ambient light, if you are using flash it must be your main light source and not simply a fill light. Well in the autoexposure modes the engineers have decided that it would be good to underexpose the ambient a little bit - up to 1 stop - and then allow the subject, illuminated by the (relatively strong, one presumes) flash, to "pop" out from the dimmer background. It also means that the additional light from the flash will not cause the background to become overexposed - if the background was metered at 0 EC and then you added flash, it would overexpose the background. This phenomenon is known as NEVEC and is documented here - http://eosdoc.com/manuals/flash/NEVEC/. To be honest I'm guessing at the reasons Canon have programmed this behaviour in. It doesn't really make much sense to me to be fiddling about, secretly adjusting relative exposure levels without letting the photographer know - none of this is documented by Canon in the user manuals, or anywhere else for public consumption, as far as I know.

If you want real control over your picture then IMHO it is way better to shoot with manual exposure to control the ambient light and then let the flash do its thing, guided by your input through FEC. At least that limits the mystery to only one variable rather than two. For shooting indoors it is standard recommended practice to shoot in manual exposure mode. You choose the ambient exposure you want for the room conditions and then let the flash top off the lighting for your subject. By bouncing the flash you get to light the room anyway, to a point, but your ambient metering will not be hopping all over the place simply because you have a little bit more or a little bit less window or bare lighting in your frame. Also, by shooting manual you make sure you bring in enough ambient light to give the room a pleasingly lit look, thus avoiding the vacant black backgrounds and viciously bright faces that seem so popular with the point and shoot crowd.

Here's an example from my most recent wedding....

The camera was set in manual mode to generally capture the ambient light within the room, with flash used just to add some pop and top off the lighting for the subject. For this shot the camera was set to 800 ISO, f/5 (I needed the DOF), 1/50, 17mm. Flash was used, bounced off the ceiling and behind me to illuminate the B&G and the cake. You will also note that there is very bright daylight through the windows at the back of the room. Had I been using any sort of autoexposure mode I would have had a nightmare of a job keeping control, depending uponn how much of those bright windows was within my frame, as I moved round the room, shooting wide, shooting long etc. etc. Manual kept the room itself more or less correctly exposed (a little bit under, on purpose) with automatic flash, sometimes with a little FEC dialed in, completing my exposure. The thing is, the brighter I kept my ambient levels the less work the flash had to do, thus making FEC less of an issue as the flash only played a smallish part in the overall exposure. I'f I'd been on autoexposure and caught the light from a window in the frame I would have had hideous results. Much of the time, if I didn't need a large DOF, I was at f/2.8, which was fine on a short/wide zoom like the 17-55, and gave me an even better ambient exposure and/or allowed me to use a faster shutter speed.

Here's another example, again with manual exposure, this time at 800 ISO, f/2.8, 1/60, 200mm. The backlighting caused me no bother at all as manual exposure kept things where I needed them to be. Bounced flash (and a little PP of the raw file) helped complete the exposure for my subject.

By the way, I do not claim to be any sort of expert on all this. I'm still learning and it's early days for me in shooting in manual and also in the pressured environment of weddings. However, I know first hand the perils of combining flash and Av mode from the results from my first wedding, two years ago, which needed simply massive correction in PP due to horrible random exposures, but mostly severe underexposure. Hopefully, from the results in my sig link, you would not know how badly I screwed up that first wedding, but the shots SOOC were horrendous.


There are some examples of adjusting the balance of flash vs ambient here....

http://photography-on-the.net/forum/showthread.php?t=499526

and some words on the subject of using FEC from a guru on the whole subject of flash, here....

http://planetneil.com/tangents/flash-photography-techniques/8-flash-exposure-comp/

Have fun

 

[Jelster]

[Lots of very good stuff.....]

However, I know first hand the perils of combining flash and Av mode from the results from my first wedding, two years ago, which needed simply massive correction in PP due to horrible random exposures, but mostly severe underexposure. Hopefully, from the results in my sig link, you would not know how badly I screwed up that first wedding, but the shots SOOC were horrendous.

Very interesting comment you make there. I was Best Man at a friends wedding last weekend and took the opportunity to take some traditional wedding type stuff, and I was really miffed when I found that my 40D, with 24-70 Sigma and Sigma flash either over or under exposed horrendously. This was while in AV mode, as I was advised that this is where the flash works "best".

I ended up shooting in manual, exposing as I would normally, and dialled in -2 stops of FEC, which allowed my fill in shots to expose quite nicely.

It's all so confusing, but I have decided to get myself a 580 EX II, as I feel sure this will help me get better control over what I'm trying to achieve.

Steve

 

[tdodd]

I think weddings must be one of the most challenging shooting situations. Not only do you have time constraints for the proceedings and impatient subjects, but from one shot to the next you might switch from bright white dress to dark black morning suit, or a bit of each, with miserable low lighting, and no flash allowed, with and without backlit windows or candles and other lighting, and then out into brilliant sunshine or pouring rain.

The best thing to do is to hope that within each location - indoors/outdoors - the ambient lighting hitting your subject will remain fairly constant, and then manual is without question your friend. Steady sunshine is OK, light overcast is better, even heavy overcast is OK, but, blotchy cloud patches with sun darting in and out are horrible. If you combine variable lighting with constantly varying tonal values in your subject then you are in for a hard slog. Even with autoexposure you'll need to hone your skills with that EC control. Once inside for the reception and evening do then manual, with or without flash, is pretty much a no-brainer.

If you're going to shoot manual with zoom lenses then really you need a fixed maximum aperture, otherwise your exposures will be all over the place depending on your focal length, unless you keep riding the shutter speed control as well as the zoom. I have the fortune (well, good sense, really) to have a 17-55 f/2.8 IS and 70-200 f/2.8 IS, but I'm seriously thinking of adding a 50mm f/1.4 and an 85mm f/1.8 to my kit bag so I can more easily shoot in low light without flash, and often the shallow DOF will be no bad thing to diminish ugly backgrounds. I've looked at the 50/1.2 and 85/1.2 and apart from the absurd pricing the performance doesn't seem to be overwhelmingly compelling so I think 50/1.4 and 85/1.8 will be good choices for weddings.

 

[KIPAX]

I see half my problem from the last couple of posts.. your talking shutter speeds of 1/50 and the like... As a sports photographer all my head thinks is speed and I never take anything less than 1/200 and usually limit to 1/250 .. I ahve never seen a decent pic of mine in slower shutter than that.

Also comments re distance. I did some head/shoulders for a team this morning.. pouring rain so indoors (arrgh) first test pointing the flash straight at a grey wall or bouncing at grey wall seemed to produce same exposure..
Then the only place I could find to take shots (clean background) was a dark blue door.. so took a shot straight on and wel and truly over exposed... bounced the light and better exposed.. upped the aperture for a perfect shot...

Was a sudden thing so still hadnt had time to read and try all the things in this thread.. basicly started with my standard settings (f5.6 1/250, iso 400) and change after test shots

 

[tdodd]

Yep, if you have a stabilised lens or a tripod, and your subject is not animated - especially if posing on purpose, and thus remaining still - then you can get that shutter speed down quite a bit. The shot at 1/60 and 200mm on a crop body (320mm equivalent) was hand held with my 70-200 f/2.8 IS lens.

Here's a 100% crop. It's not razor sharp, but 800 ISO is partly to blame for that. Also, the lens is a little bit soft wide open at f/2.8. It is better at middling focal lengths and the wide end. This was a candid, so she wasn't posing (perhaps she was ) but subject movement and camera shake was a complete non issue. I have not applied any sharpening to this image either. There will be no problem printing from this image file

For these indoor shots you are talking about, do you need to stop down as far as f/5.6, never mind f/8? Plug some numbers into here - http://www.dofmaster.com/dofjs.html - and you may find you can open up more, as well as slowing down the shutter speed somewhat. What are you shooting indoors that needs f/5.6 or f/8? A double or triple row group shot might, but for a single head/shoulder shot f/2.8 should be perfect. Also, pull your subject forwards, away from the background and the DOF blur will hide a multitude of sins.

 

[tdodd]

Here's a head shot of my nephew, taken at 50mm (nifty 50) and f/2.0. Pulling back a bit for a head and shoulders shot should give sufficient DOF for the subject, certainly at f/2.8, and also throw the background nicely OOF. I post this not to demonstrate anything about flash, as none was used here, but simply that you probably do not need f/5.6, or f/8 or even f/4 to get your subject in focus.

Here's a head & shoulders at f/2.8 1/100, 1600 ISO, 35mm on a 40D with bounced 580EX flash, fitted with an eBay Omnisphere....

 

[pxl8]

I see half my problem from the last couple of posts.. your talking shutter speeds of 1/50 and the like... As a sports photographer all my head thinks is speed and I never take anything less than 1/200 and usually limit to 1/250 .. I ahve never seen a decent pic of mine in slower shutter than that.

You need to take off your sports head and just think in terms of exposing for the light that's there, how much do you want and balance that with a workable settings.

If you're in dim light then you'll probably have to lose ambient light in favour of shutter speed but remember that the subject is being lit by the flash so the "shutter speed" for them is the duration of the flash.

Usually some negative FEC is needed to stop over-exposure as you found but it really depends on how much of the ambient light is on the subject and how much is background. If the flash is just adding a bit of fill then you need to dial it back which also helps stop the super-imposed look.

Honestly using ETTL flash seems a lot harder than it really is and I wouldn't worry too much about distance and lack of power unless you're dealing with large groups and trying to light them just with the flash.

Just do some simple tests, find a victim and get them to stand in varying types of lighting. Stick the camera in manual, expose for the ambient light and then shoot once without flash and again with. Start with around -1 FEC and see how it looks and compare with the non-flash shot. Remember the same rules for EC apply to the flash and light or dark subjects as they would for available light shots.

 

[hangerhead]

tdodd - i looked at your linked posts of the 15 shots - very good example.
which was your favourite in the 2nd row however? I think #4 for me.

The 2nd set of samples where you are controlling the flash only, the +1 FEC looked best to me - was the +1 required becuase the E-TTL system determined there was a lot of 'dark area' to be illuminated? (The purple bag)?

 

[tdodd]

tdodd - i looked at your linked posts of the 15 shots - very good example.
which was your favourite in the 2nd row however? I think #4 for me.

I agree that #4 looks the best. To be honest, despite what I have learned through reading and firing test shots I still think ETTL flash seems to give results that wander about a bit. Certainly in this shot the "subject" appears more brightly lit and pops out more, against the slightly underexposed background. I don't have the oiginal files so I can't sample brightness in each individual photo very precisely. The subject looks brighter in the last two frames but is that for real, or is it a trick of the light? Since the flsh output was constant at +0 FEC for that row of five shots it seems odd that the flash seems to output more power for the last two. Maybe ETTL calculates that we are no longer in a fill flash situation, with a very bright background, but rather that a more hefty dose of flash is required because the whole scene is effectively underexposed. That does seem to make sense.

The 2nd set of samples where you are controlling the flash only, the +1 FEC looked best to me - was the +1 required becuase the E-TTL system determined there was a lot of 'dark area' to be illuminated? (The purple bag)?

To be honest I struggle to see much difference at all between 0 FEC and +1 FEC. Even +2 FEC is not that much brighter, and it is not until +3 FEC that the whole subject goes nuclear. It looks like +1 is quite a subtle adjustment, +2 a little bit bolder and +3 is killer powerful. I wonder is the light levels are really exact stops apart with FEC, or if the figures are just for ease of reference and simplicity.

Since the blue (purple?) bag is identical in every shot, and the ambient light falling onto the bag is the same in every shot I don't see why the appearance of the various FEC compensation values seems inconsistent. The bag, being quite dark, should actually encourage the flash to fire more strongly, in order to make it come out as "middle blue". But as you will note, the stronger the flash, the stronger the shiny reflection coming back from the bag, thus probably fooling the flash. If I had used clothing, with no sheen then maybe the results would appear more consistent and predictable.

The conclusions I draw from my results are....

- you do have freedom of choice to control ambient exposure and flash exposure quite independently;

- a powerful, dedicated flash gun with high speed sync is a valuable tool for controlling the lighting ratio in bright conditions. It gives you the freedom to completely kill the background if you like, or pretty much blow it out, while doing whatever you need to do to get your subject exposed correctly;

- you do need to adjust FEC to compensate for a brighter or darker subject, in exactly the same way that you would adjust EC for ambient lighting on a brighter or darker scene/subject;

- with the best will in the world, ETTL can probably catch you off guard, if there is an item with unusual reflectivity somewhere in the scene that only highlights its presence when the flash fires. In other words, even if you think you are setting FEC correctly, or thereabouts, for your scene, you may still get a surprise. You need to check your histogram to ensure that your exposure is good and your preview image to make sure your ambient/flash balance is as you would like. Do not try to judge overall exposure just from the preview. Your eyes will lie to you, especially in dim conditions. You must check the histogram. Once you're dialed in then hopefully you can fire off several shots without too much concern, unless each time you have an entirely different tonal balance in the subject/scene. If you have the chance to shoot, chimp, adjust and shoot again if necessary then take the opportunity.