Nikon D7000: on using the flash in general, flash compensation in particular...

[DeanTaylor]

hello

A beginner asks about how using the flash interacts with the exposure factors and meters: shutter, aperture, ISO, the exposure meter in the viewfinder...

If, in manual, I set shutter, aperture and ISO, receive a centered exposure meter reading, and then decide to open the flash for use in the capture, how does this one gesture affect the three main exposure variables?

Also, to add to the mix, what effect does adjusting the flash compensation have vis a vis the exposure meter reading? That is, if the meter was centered before opting for flash, does the meter then include the flash variables in its exposure calculation?

Pardon what may be a clumsy approach to this important topic...

thank you

Dean Taylor

[george013]

hello

A beginner asks about how using the flash interacts with the exposure factors and meters: shutter, aperture, ISO, the exposure meter in the viewfinder...

If, in manual, I set shutter, aperture and ISO, receive a centered exposure meter reading, and then decide to open the flash for use in the capture, how does this one gesture affect the three main exposure variables?

Also, to add to the mix, what effect does adjusting the flash compensation have vis a vis the exposure meter reading? That is, if the meter was centered before opting for flash, does the meter then include the flash variables in its exposure calculation?

Pardon what may be a clumsy approach to this important topic...

thank you

Dean Taylor

Your lightmeter is only metering the ambient light. If you use a flash, then you add light to the ambient light.
George

[Stagecoach]

Perhaps one approach Dean would be to actually undertake those actions with your D7000, noting the affects to the metering indication and other readings.

[Mike Buckley]

If, in manual, I set shutter, aperture and ISO, receive a centered exposure meter reading, and then decide to open the flash for use in the capture, how does this one gesture affect the three main exposure variables?

If I understand your question, the answer is that it has absolutely no effect on any of those three variables. That's because you are using manual exposure mode; when using manual exposure the only thing that will change those variables is you, the photographer. As a different example, if you were using Aperture priority mode, it's possible that the camera would automatically increase the shutter speed when firing the flash than when not due to the increased amount of light in the scene.

Also, to add to the mix, what effect does adjusting the flash compensation have vis a vis the exposure meter reading? That is, if the meter was centered before opting for flash, does the meter then include the flash variables in its exposure calculation?

On your camera model, the system adds the camera's exposure compensation to the flash's exposure compensation and applies that total compensation when metering the scene. In some later model Nikon cameras, the two types of compensation are not added together.

It would be helpful in the future if you would clarify whether you are referring to the built-in flash or an external flash. Depending on your questions, the answers might be different.

[Manfred M]

Hi Dean - welcome to CiC. If you wouldn't mind completing your profile (I assume your name is Dean Taylor) by clicking on the "My Profile" tab on the top of the page and entering your name and where you are from.

As Mike has suggested, the answer to your question is dependent on your camera (D7000) and your flash. If you are referring to the built-in flash, your users manual should be a good place to start, but if you are using an external small flash (sometimes referred to as a "hot shoe flash", the answer would be at least partially dependent on the make and model.

Your flash is just another light source that gives off a brief and very bright pulse of light that lasts less than 1/1000th of a second. In many cases it is so much brighter than the ambient light that it will to a large extent overpower it with the ambient light making little or no contribution to your exposure.

The other chief property is light falloff. Nicely said the further away from the subject, the less light will reflect of your subject and back to the camera. The inverse square law describes how much dropoff there is, based on the distance from the flash.

If you flash on manual, you have to determine the proper exposure through trial and error, calculating the exposure using the flash's guide number (GN) or using a flash meter to measure the flash. You set the intensity required based on the aperture and ISO you are shooting at. Shutter speed (so long as it is no greater than your camera's synch speed) will likely have little to no impact on your exposure. Your camera's light meter reading is totally irrelevant, as it measures the ambient light when you are using it and does not incorporate the light from the flash (again in manual mode).

If you are using the TTL mode (a level of automation) and you are using either a Nikon flash (built-in) or one of the external units that are CLS (Nikon's term - Creative Light System) compliant (all of the flashes that have been released over the past number of years are) or a third part flash that is CLS compatible (many are not), the your camera will fire a pre-flash and measures the reflected light using the light meter in the camera, based on the ISO and aperture and sets your flash power to illuminate your subject "properly" and fires the flash. This happens so quickly that you will not see two separate flashes firing. I'm not 100% certain, but suspect that your camera will use the metering mode that has been selected to do the light reading.

Flash compensation is a way for you to override what the meter is telling the camera to do in the TTL modes (no impact on manual). If your image comes out looking too light or too dark, this is one thing you can do to compensate. You can dial in the amount of compensation either from the camera (press the camera's flash button and use the camera's command dial) or if you are using a Speedlight you can also enter the amount of compensation directly into the flash.

[DeanTaylor]

If I understand your question, the answer is that it has absolutely no effect on any of those three variables.

"If, in manual, I set shutter, aperture and ISO, receive a centered exposure meter reading, and then decide to open the flash for use in the capture, how does this one gesture affect the three main exposure variables?"

When I wrote, how does it affect the (three) variables, it was meant: how does adding the camera's flash affect the need for me to then go and change the three variables myself...

also...

the phrase, "and then decide to open the flash for use in the capture..." may have been a bit vague, when open implied raising the camera's built-in flash.

Pardon me...



Best,

Dean

[Mike Buckley]

When I wrote, how does it affect the (three) variables, it was meant: how does adding the camera's flash affect the need for me to then go and change the three variables myself...

The flash will add more light to the scene. So, my method when using manual exposure mode would be to take the photo and check the histogram. If it indicates that I need to make an adjustment, I would adjust the flash output and/or any of the three exposure variables, depending on my needs.

[Stagecoach]

One other consideration is that if you are in 'Manual' and have a 'speed' set greater than the flashes sync speed on opening the flash (referring to onboard one) the cameras 'speed' may be automatically set to the sync speed on the D7000 if it works as the D300.

[Manfred M]

Dean - if you are just a beginner, why don't you just leave the flash in TTL mode and let the camera figure out the right exposure. The D7000 is a sophisticated camera with a lot of processing power. One thing that I will admit, I've never shot my built in flash on manual.

[Mike Buckley]

Dean - if you are just a beginner, why don't you just leave the flash in TTL mode and let the camera figure out the right exposure.

I don't consider myself a beginner but in this situation that's exactly what I would do.

[DeanTaylor]

I don't consider myself a beginner but in this situation that's exactly what I would do.

My rationale is that, as a beginner, I would want to experience as much of the image-capture 'process' as possible--for the sake of the learning event as well as the fun of...'being there'...(i.e., 'to be involved'...)


thanks to one and all for informed--and, generous!--commentary.

Best,

Dean Taylor

[Mike Buckley]

Dean,

Each of us has our own learning process. One extreme as it applies to mastering a camera's capabilities is to begin doing everything manually. The other extreme is to master the capabilities by beginning with as much automation as possible. If using the manual method moves you reasonably well along the learning curve with minimal frustration while providing the enjoyment of "being there," that's fine. However, if that doesn't seem to work well for you, try beginning using the other extreme and make gradual, systematic changes until you feel comfortable working fully manually.

[Manfred M]

Dean - I personally would not spend too much time figuring out how your built-in flash works on manual. These units have very limited functionality and I have virtually never used it as a flash, just because of its limits; power, inability to swivel the head, close prxoimity to the optical axis of the lens. For a number of reasons, these things really don't work particularly well for as a standalone flash for photography.

Pretty well the only thing I use it for is as a master to trigger off-camera Speedlight slaves. Even here, I only do this when I have not brought my electronic triggers along.

[george013]

My rationale is that, as a beginner, I would want to experience as much of the image-capture 'process' as possible--for the sake of the learning event as well as the fun of...'being there'...(i.e., 'to be involved'...)


thanks to one and all for informed--and, generous!--commentary.

Best,

Dean Taylor

I know exactly what you mean.
As I said, your flash is adding light to the ambient light. This can be done in rougly 2 ways: manual or ttl. In manual you can set the power of the flash with a button. In ttl Nikon uses a preflash. The camera measures the preflash and calculates the power of the mainflash. If you have an external Nikon-flash on the camera with the head aimed to the front, it might be able that the distance is used to.
Some explanation http://nikonclspracticalguide.blogsp...-metering.html

The shutterspeed is limited at the fast site by the synchronisation speed, at the slow site by a variable called something as slow. I dont'know the exact name of it now. That's probably set on 1/30, you can make that 30s. That's what I advise you to do.

George

[pnodrog]

Just keep in mind if you have the camera in manual and adjust the exposure for the ambient light then raise the flash the correction to maintain the exposure will be dependent on the distance to the subject.

[jcuknz]

"If, in manual, I set shutter, aperture and ISO, receive a centered exposure meter reading, and then decide to open the flash for use in the capture, how does this one gesture affect the three main exposure variables?"

When I wrote, how does it affect the (three) variables, it was meant: how does adding the camera's flash affect the need for me to then go and change the three variables myself...

also...

the phrase, "and then decide to open the flash for use in the capture..." may have been a bit vague, when open implied raising the camera's built-in flash.

Pardon me...



Best,

Dean

When I started using flash [ single use flash bulbs ] I was introduced to the Guide Number applicable to the flash bulb and from the GN one found out the aperture to use. Shutter speed only affected the amount of ambient light and for mixed lighting [ ambient plus flash ... or syncro sunlight ] one worked out the required aperture from the GN and the shutter speed appropriate to use with that aperture .... in those days everything was 'manual' and when I got myself an electronic flash it remained the same .... GN56 meant f/5.6 at ten feet flash to subject distance f/8 at around 7' and f/11 at 5'. Later I got a flash with a GN of 80 which was twice the power of my original unit.

Fast forward to the digital age and I am completely lost and still fumbling with automatic flash units and dam clever cameras which balance the light they receive as they make the exposure and seem to give quite a good result if the flash is cut back a stop. The nearest I have got to manual is using Shutter priority to set the aperture to suit what I believed might be the GN of my 'on-board' and the distance to the principle subject ... subsequently seeing how well the camera does its job I remain in A mode and just open the flash to 'force flash' ... not a very clever solution but it seems to work AOK
Finally I would mention that there is a popular misconception that working in Manual is the way the experts work .... maybe I'm not an expert but I rarely use M unless it is obvious that A will not produce the result for some reason. So I suggest for a newbie is "Trust your camera" until it doesn't produce what you want and only then override its clever brain and hopefully you will get it right

Finally[2] if you have a means of reading EXIF take a shot with and then without flash and compare the EXIF readouts.

Edit ... these days when I am in manual I am using the camera to tell me what exposure to give but estimating how much over or under what the camera thinks is correct for the subject. I find that idea somewhat humbling

[DeanTaylor]

Finally I would mention that there is a popular misconception that working in Manual is the way the experts work

hello

Yes, a pro like Ken Rockwell (whose informed commentary I find to be quite useful) agrees with you--it is useful for me now as it provides full interaction (the usual reason cited by earnest students).

I also made the happy acquaintance of Darrell Young's insights on the flash issue--as you know, his writing makes seemingly obscure topics completely accessible...for example, here:

http://is.gd/SfSgdY

here:

http://is.gd/Ot2AMN

and here:

http://is.gd/84pbP4

Best,

Dean Taylor

[jcuknz]

Your first link to Darrell suggests to me that he is writing a whole lot of garbage to fill a space
"A guide number was found when I first used them in around 1954 as the aperture used when shooting with 100ISO/ASA film when the flash to subject distance was ten feet and the subject was of 'average' tonality. Found when one multiplies the aperture number by ten/distance [ or roughly 3 for a metric GN ]"
But of course in those days we didn't have variable powered and variable coverage flash units along with intelligent cameras ....and life was nice and simple.
The second and third links are of no great interest as I mainly shoot Panasonic these days.
What little I have read of Ken suggests he is prepared to challenge established concepts with common sense, to the enragement of the establishment

[dje]

Dean I tend to think of fill flash as a combination of two exposures, one from the ambient light and one from the flash. If you are in M mode and have Flash control set to iTTL, the flash output will still be automatically controlled by the camera to get the flash exposure of the main subject right (and it will take the aperture and ISO settings into account in doing this). The background brightness (which will be more affected by ambient light as flash strength falls off with distance) will be affected by the shutter speed, aperture and ISO setting and you can control these how you see fit. For example you might choose aperture for a desired DOF and ISO to adjust background brightness. The max SS will be limited to the sync speed (probably 1/250 sec).

Dave