Aperature mode and fill flash

[Dingerkingh]

Let's say I am using aperature mode where the shutter speed is automatically picked. At first I take a picture without the flash. Then, I take a picture with the flash. Does the camera make any adjustments to the shutter speed because it knows the flash is on? Furthermore, does the camera make further adjustments to shutter speed I f you dial the flash back by a stop? More or less I am trying to take photos in which the light might be behind or to the side and I am attempting to brighten the faces. Thanks for any help!

 

[WayneF]

Let's say I am using aperature mode where the shutter speed is automatically picked. At first I take a picture without the flash. Then, I take a picture with the flash. Does the camera make any adjustments to the shutter speed because it knows the flash is on? Furthermore, does the camera make further adjustments to shutter speed I f you dial the flash back by a stop? More or less I am trying to take photos in which the light might be behind or to the side and I am attempting to brighten the faces. Thanks for any help!

You did not say Nikon or Canon, and both questions depend...

Shutter speed adjustments: Indoors yes, outdoors probably not.

Indoors, the Minimum Shutter Speed With Flash kicks in, and in camera A mode, you probably always get 1/60 second shutter speed indoors with flash (dim, where you need flash). With the flash turned off, it may meter much slower, maybe like 1/4 second even, but there is no reason to use the slow shutter speed if you are using flash. So it has a Minimum Shutter Speed With Flash. You may see that change. But shutter speed only affects ambient. Shutter speed does not affect flash exposure.

Exceptions are, you can choose Slow Sync to override this and use the 1/4 second, or whatever it meters (to pick up the weak ambient). If a Nikon, then Rear Curtain sync does the same as Slow Sync, but I think Canons do not do this for Rear sync. Rear sync only makes sense with slow shutter speeds however.

Outdoors, like fill flash in sunlight, the shutter speed will already be much faster than Minimum, so no difference (Minimum has no effect). The problem outdoors is the Maximum Sync Speed with flash, probably around 1/200 second (flash cannot use faster). So outdoors, with camera A mode, if you naively set say f/4 without thinking, you just get error, since with flash, it cannot advance shutter faster than 1/200 second (whatever sync speed is) that sunlight requires. With camera A mode, you have to know to start up around f/11 in the sunlight. Or, using camera P Mode knows this - how to do fill flash in sunlight.

Re: Dialing back flash. If using Flash Compensation of TTL flash, there no adjustments to shutter speed from flash compensation (and of course, not from manual adjustments of manual flash mode either). Said another way, the light meter we see, the one which adjusts the camera settings, is NOT about the flash - it affects only the ambient light. The flash TTL has its own invisible meter and system, and it adapts to whatever camera settings it discovers to be in effect. It adjusts flash power to match the aperture and ISO in effect. It never changes camera settings (except the Minimum and Maximum sync just mentioned).

If you try to do this dialing back with Exposure Compensation, it affects only ambient on Canons, and affects both flash and ambient on Nikons.

 

[Dingerkingh]

Sorry - I am using a Nikon D5200. I only have the built in flash (bad I know). What you wrote makes sense but also made me how little I understand about using flash. I guess my biggest concern was if I snap a photo and I like ambient lighting but subject is too dark - can I just pop up the flash and not have to worry about over exposing. Or how to know whether to step the flash down or let it go full power. Thanks again for your reply!

 

[Gavjenks]

The camera has no way of knowing what the appropriate settings are, because it doesn't know how far away stuff is, and flash is 1/4 dimmer every time you double the distance.

It might be able to guess your subject by assuming the flashed distance is the focal distance of your lens, for some brands (e.g. Canon ETTL II), but that's a rule of thumb type of thing, not proper metering per se. Still not as good as knowing how to do it yourself, since your subject might not be exactly where your focus point is, or you may need to worry about overexposing foreground non-subject stuff, etc.

Usually the only way the camera does it is if you allow it to do those horrible pre-flashes that blind everybody and ruin your photo by screwing up everybody's expressions. In addition to the horrors of on camera flash in the first place, it's not a very winning situation. And even then, it's not ideal compared to you judging yourself (same thing: possible overexposure of foreground, etc.)

But yes, it will be semi-competent, usually, if you're not in manual mode.

 

[runnah]

Where in Maine are you at?

 

[sk66]

You did not say Nikon or Canon, and both questions depend...

Explained very well.
The only point I would make is that in P mode the camera uses the flash as the primary light source (i.e. not fill). It may not matter if there is no real need for the flash in the first place, but it's not "trying to balance."

We have also left out the considerations of HSS/FP and BL(Nikon) modes if using an external flash. The pop-ups on newer Nikons are automatically in BL mode (no symbology though) when using A/S priority modes (cameras after ~ D300; not certain of the specifics)

 

[WayneF]

Sorry - I am using a Nikon D5200. I only have the built in flash (bad I know). What you wrote makes sense but also made me how little I understand about using flash. I guess my biggest concern was if I snap a photo and I like ambient lighting but subject is too dark - can I just pop up the flash and not have to worry about over exposing. Or how to know whether to step the flash down or let it go full power. Thanks again for your reply!

Yes and no. Saying, there are situations and choices. Saying, there are no yes or no answers.

We don't necessarily need flash if the ambient exposure ought to be OK, but just isn't quite the right exposure. This happens, but adding flash may not be the first response. And also, flash has a limited range or reach, esp the internal flash is pretty weak.

Multiple topics here, it is a pretty big subject...

That "not quite right exposure" frequently happens with reflective meters (like in the camera), because it is affected by the colors of the subject.

For example, any scene of mostly light color (like white), for example snow outdoors, or a white background wall indoors, will be underexposed.
Any scene of black or mostly dark colors will be overexposed. That is guaranteed, it is simply how reflected light meters work. They can only aim for a middle gray result, not too bright, not too dark, regardless what it should be, because that is all they are able to do. It is just a dumb computer chip without a brain to know what it is seeing, or how it ought to be. Howver, it can measure the light, without knowing what it means, so it aims for a middle gray result, not too bright, not too dark. Average scenes (mixture of light and dark colors) do come out about right, but there are exceptions. Flash metering works exactly the same way, reflective meters. More at How light meters work It greatly helps to realize this.

Anyway, flash may not be the first reaction. When the exposure result is not quite right, then we simply correct it with compensation (may not need the flash). We use Exposure Compensation to adjust the ambient result, or we use Flash Compensation to adjust a flash result (on the D5200, and most other Nikons, Exposure Compensation affects both ambient and flash, both are considered exposure). We simply do what we see we need to do, with Exposure or Flash Compensation.

We do use flash, for several reasons. One is when the ambient is too low, hopeless. Typically indoors, we could not care less about the ambient because it is so far down, dark. And we use flash to modify the shadows, like fill flash in bright sun, to fill the dark shadows on the face. And we use flash when we want to modify how the light is distributed, by design instead of chance. But it would likely be inappropriate for a landscape scene for example.



Re: worry about flash overexposing: Yes, the system can handle that when turning the flash on. Because the internal flash (and a SB-400 or SB-700 flash too) work in TTL BL mode by default. That BL is Balanced Fill flash mode, which means if in bright light, the flash exposure is automatically held back (balanced means reduced flash) so that the sum of the two exposures (ambient and flash) wont overexpose. There is lots about this at Four Flash Photography Basics we must know - Flash pictures are Double Exposures

However, if you select Spot metering (the flash does not use Spot metering, it is only about the ambient), but it does switch the flash from TTL BL mode to be what is called TTL mode, which is "regular flash" (NOT balanced flash), and then yes, adding flash comes in strong, as if there were no ambient, and yes, then the sum will definitely overexpose (a proper ambient exposure and a proper flash exposure is 2x the light, which is one stop overexposed, at least on the near subject).

So for example, fill flash in bright sun is very popular to help the dark shadows on faces (it is wonderful). If using regular flash, we have to know to use about -2 EV flash compensation to prevent blowing out the subject. But TTL BL mode (which is default for most flashes) knows to handle this automatically, and it dials back the flash back about -2 EV.

 

[WayneF]

The only point I would make is that in P mode the camera uses the flash as the primary light source (i.e. not fill). It may not matter if there is no real need for the flash in the first place, but it's not "trying to balance."

Agreed if the ambient is dark (indoors), there is no need to balance. And Nikon models have gotten better about it, but TTL BL mode is often still down a little in those cases. Lots of things affect that comparison though, D-lens distance is switched off in regular TTL mode and FV Lock mode, which is a big effect (negating incorrect D-lens distance in zooms). In P mode with flash also then enforces a maximum aperture too (which is pretty wide, but is also reduced by ISO too). There are many things happening in there.

I would disagree with saying the first sentence that way. I think you are obviously only referring to these dark ambient cases you mentioned. Because otherwise, the ambient metering system always meters the ambient, and only the ambient. P mode adjusts shutter and aperture (and maybe ISO) settings to do that ambient (the flash has not fired yet). The only change flash presence will make to those settings is the Minimum and Maximum sync speed. (and in some cases, ISO is also held back, but this varies greatly with models, Nikon iTTL has at least three versions of that action).

The flash metering always meters the flash (a different system seeing the instant preflash). It always uses the same aperture and ISO it discovers to be in effect (does not change settings), and it tries to match them with flash power level. That cannot be called primary.

The camera metering system combines the two exposures for TTL BL mode, and holds the flash back if significant ambient. But the ambient comes ahead on full, regardless if flash or not. Certainly it does not consider flash is the primary light (except maybe we could say it that way for the dark scenes where there is no ambient, i.e., flash is required - but primary is not the word). I think that is what you must have meant, specifically just about those dark ambient cases, but balanced flash is more about fill flash in bright sunlight.

 

[sk66]

I don't think Nikon's are using BL if in P mode (maybe with an external flash set to BL and not using spot metering). I understand your point about using the word "primary." I simply meant it will use as much as needed without regard to anything else. In P mode the camera knows it has full use of the flash and will therefore tend to choose settings based upon the flash as the available ("primary" consideration) light source (i.e. it tends to choose lower ambient exposure/"better" camera settings). If outdoors and the camera can already use the "better" settings then it's of no affect. But TBH, I don't use P mode with flash so I'm not 100% certain...

I essentially agree with you. Different metering patterns/logic between the systems (same sensor), talking/not talking, etc...
Flash on/off doesn't really affect the camera's behavior for any specific mode. i.e. *what* it adjusts and in what priority, but it may affect the range of control available... the specific camera mode/flash mode affects how the flash is utilized.. I'm pretty certain that's what you are saying as well.

I think we've gone well beyond the basic question initially asked which is why I didn't expand on my comments originally... This can all get very confusing very quickly. Especially since a lot of the information one finds is about manual camera/flash and is really not accurate for TTL work.

 

[Designer]

Let's say I am using aperature mode where the shutter speed is automatically picked. At first I take a picture without the flash. Then, I take a picture with the flash. Does the camera make any adjustments to the shutter speed because it knows the flash is on? Furthermore, does the camera make further adjustments to shutter speed I f you dial the flash back by a stop? More or less I am trying to take photos in which the light might be behind or to the side and I am attempting to brighten the faces. Thanks for any help!

As I understand it, the camera senses the flash by detecting a "return", or the portion of the flash light that is reflected back toward the camera and into the sensor. That is when the camera adjusts the shutter speed and/or the ISO as needed to produce an acceptable exposure.

You say you are trying to use the flash to "fill". There is a setting for that. Consult your user's manual. It is called "Flash Control for Built-in Flash".

 

[WayneF]

I don't think Nikon's are using BL if in P mode (maybe with an external flash set to BL and not using spot metering).

Yes, it does. P mode is not different. For any TTL flash without the overt TTL/TTL BL menu (the SB-600/SB-800/SB-900 have this overt menu), the flash will default to TTL BL mode. Including P mode. The menus are abbreviated TTL, but the action and result is TTL BL (meaning balanced flash, meaning reduced flash due to bright ambient). Nikon is a TTL BL system, and a good one, but they have made some of it be confusing and arcane.

That TTL BL mode default includes the internal flash, the SB-400, SB-700, and the Commander with any flash. It includes many if not most third party flashes (those doing iTTL without overt TTL/TTL BL menu), but I do believe there are few exceptions, depending on firmware level they report to camera). The camera is what does the metering modes, the flash just responds to orders.


The only exception to the TTL BL above is when the camera is set to Spot Metering, which always changes the iTTL metering mode to TTL (never TTL BL in any case). The flash does not do Spot metering, but Spot is only about the spot, and the concept of balancing flash to ambient loses all meaning.

P mode is certainly Not an exception regarding TTL BL mode. P mode and TTL BL flash mode is point&shoot fill flash in bright sun (i.e., a little more aware of the situation than is A mode, where we idiots can set an aperture that can make it impossible ).

I understand your point about using the word "primary." I simply meant it will use as much as needed without regard to anything else.

I can agree with that definition. Balancing flash with ambient that is 6 stops down has no meaning either. But when ambient becomes significant level, then ambient remains primary, selecting the camera settings used. The TTL flash matches those settings with power level.

In P mode the camera knows it has full use of the flash and will therefore tend to choose settings based upon the flash as the available ("primary" consideration) light source (i.e. it tends to choose lower ambient exposure/"better" camera settings). If outdoors and the camera can already use the "better" settings then it's of no affect. But TBH, I don't use P mode with flash so I'm not 100% certain...

Disagree, and I'm puzzled what gives that impression? What P mode does is to set both shutter speed and aperture based on ambient. So it does know about and honor Maximum Sync Speed (same as A and S mode), and will not exceed sync speed in bright sun. But it can control aperture too, so it won't try to use f/4 for fill flash in bright sun which cannot work.

There are only three differences in P mode and A mode, and two are about aperture and flash.

1. P mode can change aperture, and of course sets both shutter and aperture. Where A mode only sets shutter speed for the aperture we manually select. Both cases are in regard to the ambient, not the flash (except the Minimum and Maximum shutter noted - but flash exposure is not affected by shutter speed, but ambient of course is).

2. Except, P mode introduces a Maximum Aperture with flash, which numerically varies very slightly among models, but maximum is either f/4 or f/5 for hot shoe flashes, and ballpark of f/2.8 or f/3.5 for internal flashes. Further this maximum aperture stops down even more, 1/2 stop for each stop of increased ISO - so at high ISO, the maximum aperture might be like say f/8 (flash in P mode). The manuals for higher models have these charts, the lower models probably don't. That is really not about the flash, they say it is about ability of the metering system to handle those EV numbers (however I am unable to say why A mode is different, or why internal flash is different). But even if you bought a f/1.8 lens, P mode will never use that aspect with flash (the other modes can).

And 3, in Auto FP, HSS normally kicks in when shutter speed exceeds the trigger speed. That is the Auto aspect of it. In camera A mode, if using HSS in bright ambient where the shutter speed is very near trigger level, slight variations (passing clouds, etc) can therefore go past the trigger, and kick FP in or out, causing unexpected huge changes from one second to the next.

This possibly might be behind your thinking that P mode chooses better settings? Because P mode is different, it can change aperture, and will - the lens will first stop down all the way, to f/32 if it can, before it will allow PF HSS to kick in. You can spin it in, but it won't go willingly.

A mode cannot change the aperture, so it can not do these actions.

But there are no other differences in P mode, and none in regard to TTL vs TTL BL flash.

The only thing forcing TTL mode over TTL BL mode is either Spot metering, or an overt menu on the flash. True in any camera mode, A, S, P, M.

I think we've gone well beyond the basic question initially asked which is why I didn't expand on my comments originally... This can all get very confusing very quickly.

I agree.

 

[sk66]

You're going to make me have to go play around w/ P mode and I don't want to do that...

FWIW (not much), I learned Nikon TTL using SB600/800's and D200/D300/D3...and *how* I use TTL hasn't changed much since having changed bodies. The only real change is I now prefer matrix metering for TTL work since that seems to make the flash metering and camera metering more alike. That being the case, the fact I haven't studied it in detail any time recently, and the fact I don't use P mode (well almost never) certainly means I'm not the best authority on this and I'm willing to learn something new.

If what you are saying is true, then in P mode one would expect the camera to use longer SS's/higher ISO's/wider apertures as necessary for the ambient... but it doesn't. It chooses "better" settings based upon it's program curve and adds flash as necessary. Doesn't it? Or have they completely re-done the way the camera works with flash and P mode? (I haven't heard/read anything indicating that, but it's not high on my radar).

Yes, the camera only ever meters the ambient, it can't do otherwise. And yes, the camera metering and the flash metering only ever talk when in a BL mode. I was unaware that P mode is also using BL by default... I haven't seen anything that says it is/isn't, but I do know that BL is now Nikon's default mode for flash so that makes sense.



I apologize for the hijack...

 

[WayneF]

You're going to make me have to go play around w/ P mode and I don't want to do that...

FWIW (not much), I learned Nikon TTL using SB600/800's and D200/D300/D3...and *how* I use TTL hasn't changed much since having changed bodies. The only real change is I now prefer matrix metering for TTL work since that seems to make the flash metering and camera metering more alike. That being the case, the fact I haven't studied it in detail any time recently, and the fact I don't use P mode (well almost never) certainly means I'm not the best authority on this and I'm willing to learn something new.

Yeah, I still use two SB-800 myself. They were nine years old, and I finally sent them to Nikon for the routine service check. They were working fine, but they put new flash tubes in them, which gives me a little higher WB now, more like a new flash. And just recently, I added a Yongnuo YN565EX just to see what the excitement was about. Only about $100, and the same power as a SB-800, and it even works remotely with the commander the same way. It is indeed exciting. Some of the frilly options seem incomplete and don't work, at least not in the Nikon version. Maybe next pass? But all the basic operation seems very solid, it just works.

I don't use P mode either, flash is either camera Manual for indoor or often usually A mode for outdoor. But P mode is very beginner friendly point&shoot TTL BL fill flash in bright sun. Wedding photogs call it Professional mode, because they can move indoors or out without changes. With A mode, they would have to shift from like f/5 to like f/11. P mode does that for them.

I have never understood why Nikon removed the TTL menu. The menu can't cost anything, a few bytes of ROM. TTL is normally my choice, even for fill flash (which of course, does have to be tended to). But IMO, the only thing that the automation of Matrix mode or TTL BL mode can ever do is to surprise me, and I hate surprises. Center Weighted metering just seems more natural to me, and TTL flash too... I just know what to expect they will do when the system doesn't meddle with it.

And actually, the flash metering is center metered too, not the same center weighted area, but a smaller similar central area. Flash does not use Spot metering, and does not use Matrix. However, TTL BL level can be influenced by ambient metering, which could be matrix. This picture might help: Details about Metering Principles

And you mentioned D300, see manual page 180 under FV Lock, it says 4mm in the center (half the default Center size). It also does say Commander uses full frame, but I cannot verify that... seems to me commander sets both flashes equal in the center. D800 page 190 says 6mm, which is 1.5x larger. But... there is so much else always going on too. For example, FV Lock and TTL mode and Spot metering (which is TTL mode) also ignore the D-lens distance, which is often kinda badly wrong in most zoom lenses (so ignoring it turns out to be a good thing. ) Things like that are where the surprises are.

If what you are saying is true, then in P mode one would expect the camera to use longer SS's/higher ISO's/wider apertures as necessary for the ambient... but it doesn't. It chooses "better" settings based upon it's program curve and adds flash as necessary. Doesn't it? Or have they completely re-done the way the camera works with flash and P mode? (I haven't heard/read anything indicating that, but it's not high on my radar).

Well, I don't think it was me that said those words. Longer/higher/wider/better than what? The other modes A, S or M can only do what we set them to do. They have no choices. That's how I would say it.

I am not aware they redid P mode. iTTL has always been that way (SB-800 lifetime). P mode is the one that does have choices of equivalent exposures, which sometimes differ from my own choices, but it only seeks a proper ambient exposure, and the flash fills in with flash level. Indoor P mode flash surely will be f/4 or f/5 with hot shoe flash, and probably always 1/60 second unless we controlled it slower. I would call it fixed instead of automatic. At least, there must be other choices we could consider. But P mode is TTL BL unless some overt menu otherwise overrides the system, or unless spot metering.

Just check the Exif, P mode will say TTL BL in there (unless Spot metering is on). And of course, the results will represent TTL BL.

If the SB-800 the mode will be what the flash menu says it will be. . That is where it is set, not because of P mode. And again, if Spot metering, the flash menu will change from TTL BL to TTL.

 

[table1349]

Let's say I am using aperature mode where the shutter speed is automatically picked. At first I take a picture without the flash. Then, I take a picture with the flash. Does the camera make any adjustments to the shutter speed because it knows the flash is on? Furthermore, does the camera make further adjustments to shutter speed I f you dial the flash back by a stop? More or less I am trying to take photos in which the light might be behind or to the side and I am attempting to brighten the faces. Thanks for any help!

Even better than letting the camera think for you, just learn the art of fill flash.
Flash 101 (Fill Flash In Use) | The Wonder Of Light

Camera Flash: Appearance

 

[hirejn]

Some cameras will automatically reduce the shutter speed to one that will sync with the flash. Shutter speed never affects flash exposure itself. It can't for reasons of physics. What it does affect is whether the flash syncs with the shutter. The flash waits until the first curtain is fully open before it fires. Then the whole frame is illuminated when the flash goes off. At higher speeds, the second curtain begins to close before the first curtain is fully open, so when the flash fires part of the frame is covered by the second curtain, so you get a black bar. High speed sync solves this, but if it's not turned on the camera may prevent the shutter from going past the sync speed, usually 1/250. However, it should automatically adjust the other variables. The important thing is shutter doesn't affect flash exposure, only flash sync. Dialing flash power has no effect on shutter speed.