Getting to grips with flash

[Mingmoos]

Hi all, hope someone can point me in the right direction. I am using an external flash unit on my Sony A7. In a reasonably well-lit room with the camera set to manual, shutter set to 1/60,aperture f1.8 and ISO set to auto, I get a well-exposed picture, however the ISO is in the region of 1600 to 3200. As I would prefer the ISO to be lower, I have kept the above settings except that I have the ISO fixed at 100. I now find that before I press the shutter the settings in the viewfinder tell me the shot is going to be very underexposed. Do I go ahead and take the shot and will the flash power increase to take account of the lower ISO of 100, resulting in a well-exposed picture I have a lot of experience of outdoor photography, but flash seems to be a whole new ball-game altogether. Any thoughts on the matter would be appreciated.

[pschlute]

Ignore the viewfinder meter reading, it does not know you are using flash.

If your flash is compatible with the camera in some form of TTL mode then yes the flash will provide the correct power for your shot. The limitation may be if the distance from flash to subject is too great but you need to try it first.

I do not use a mirrorless camera so this may be wrong but perhaps there may be a setting you have to enable to ensure your camera uses the mechanical shutter rather than electronic shutter also.

[DanK]

I have don't use that camera, but if you are reasonably close to the subject, a moderately powerful flash set to TTL mode should be fine. TTL (through the lens) means that the camera and flash monitor the light through the lens and shut the flash when the exposure is reasonable.

I do many of my candids of kids (generally quite close range) in manual mode, 1/60, f/4.5, ISO 400, TTL flash, using a Canon 430 EX II, which is not one of their most powerful flashes.

Note that if you are using TTL mode, the ISO setting will determine the impact of ambient light as well as the duration of the flash. That is why I use 400 rather than 100 as a starting point, even though I use 100 for most other things. ISO 400 gets me enough exposure of the setting from ambient light that the person doesn't stand out against an overly dark background.

[Manfred M]

James - flash photography is a whole different "game" when compared to regular photography.

In regular photography we deal with three main variables when it comes to exposure; the ISO, aperture and shutter speed. When we shoot flash, two more variables come into play; distance from the flash to the subject and the flash power. Proper exposure of a subject with flash is governed by the inverse-square law that essentially says when you increase the flash to subject distance, the power level required is squared. Simply stated if you double the flash to subject distance, your power setting has to increase by a factor of four (2^2 = 4).

This suggests that anything in front of your properly exposed subject will tend to be overexposed and anything behind the subject will be under exposed due to flash drop-off.

[Stagecoach]

Hi all, hope someone can point me in the right direction. I am using an external flash unit on my Sony A7. In a reasonably well-lit room with the camera set to manual, shutter set to 1/60,aperture f1.8 and ISO set to auto, I get a well-exposed picture, however the ISO is in the region of 1600 to 3200. As I would prefer the ISO to be lower, I have kept the above settings except that I have the ISO fixed at 100. I now find that before I press the shutter the settings in the viewfinder tell me the shot is going to be very underexposed. Do I go ahead and take the shot and will the flash power increase to take account of the lower ISO of 100, resulting in a well-exposed picture I have a lot of experience of outdoor photography, but flash seems to be a whole new ball-game altogether. Any thoughts on the matter would be appreciated.

With using flash a good thing to always remember is that the captured image will be a combination of two light sources, the ambient light in the room, if any, that may be daylight or artificial and then there will be the light added by your flash.

The meter is showing you the result of the cameras measurement of the 'ambient' light present of which may be of interest to you. As a simple example lets suggest you have a person back-lit in front of a bright window and were going to use the flash for fill light of their face, your meter reading would be important to ensure that the 'ambient' window light was not overexposed.

[Geoff F]

Set your Iso manually as well, James.

Do you really want settings of 1/60 and wide open aperture for what you are photographing? Those settings were typical for the old film days with a fixed output flash; but everything is different now. Shutter speeds can be as high as 1/200 or higher when using high speed flash. Wide open aperture may suit some situations but I often work at F11, particularly with macro work.

TTL flash metering will automatically take care of the variation required to balance out your manual settings but after a few test shots you may want to add or subtract a little bit of flash output compensation. This works in a similar manner to exposure compensation although there are a few limitations so you may need to adjust your camera settings to fit within the limits of available flash compensation etc.

[dje]

I now find that before I press the shutter the settings in the viewfinder tell me the shot is going to be very underexposed.

James I checked on my A7 with a Godox flash attached (set to TTL). When looking through the viewfinder, the exposure meter indication does look low corresponding to the exposure for ambient light only. However when you half-press the shutter, the exposure indication reads OK. I think this is just an indication that the camera recognises that there is a flash connected. When you fully press the shutter, TTL steps in with a short pre-main flash metering flash. This ensures that the exposure for flash is about right.

Dave

[rpcrowe]

Try this and then branch out...

Select your ISO somewhere between 100 and 400 should give you pretty decent shutter speed and f/stop.

Set your camera to programmed exposure.

Set your flash to TTL is you have a TTL compatible combination.

If you do not get your exposure right on with this combination, then use the programmed exposure as a starting step and shift to manual camera exposure.

After gaining some experience with this method, you may if you desire, be able to eliminate the programmed exposure step altogether and shoot with manual camera exposure and TTL flash exposure...

[William W]

. . . I am using an external flash unit on my Sony A7. In a reasonably well-lit room with the camera set to manual, shutter set to 1/60,aperture f1.8 and ISO set to auto, I get a well-exposed picture, however the ISO is in the region of 1600 to 3200. As I would prefer the ISO to be lower, I have kept the above settings except that I have the ISO fixed at 100. I now find that before I press the shutter the settings in the viewfinder tell me the shot is going to be very underexposed. Do I go ahead and take the shot and will the flash power increase to take account of the lower ISO of 100 . . . ?

The "settings" in the viewfinder assumed is the Camera's TTL Light Meter Display - that's displaying the reading of the Ambient Light in the Scene.

If the Flash is communicating with the camera (meaning that the Flash is capable of and is also set to TTL Mode) then yes, the Flash will adjust its output to "correctly" light the Subject/Scene, provided that you are not beyond the Maximum Flash Working Distance (meaning - provided you are not too far away in distance and thus exceeding the Flash's maximum power to light the scene adequately).

As already advised, set the ISO manually.

Also as already mentioned, a good concept to use when using Flash, is thinking about the final exposure as a combination of the Ambient Exposure and the Flash Exposure.

As a practical example of using this concept, when you used the manual camera settings that you described (F/1.8 @ 1/60th @ ISO100), and looked through the viewfinder, you noticed that the TTL meter displayed that the image would be underexposed: if you were to increase the ISO incrementally 200, 400, 800 etc, you would notice that the TTL Meter would display LESS underexposure - that's giving you an idea of how much influence the Ambient Exposure will have on the Final Image.

This is termed the BALANCE of the Ambient and the Flash. In your example when you use ISO100 the Flash will be more dominate than when you let the camera select ISO1600~3200.

There are times when you might want the Flash very dominate and there are times when you might want the Flash to be acting more as a Fill, to a more dominate Ambient - this should be YOUR choice and that is why I suggest that you begin these choices by setting the ISO manually.

One simple way to get to grips on this is doing exactly that exercise and make the same image with different ISO settings and compare them: digital is very inexpensive and provides very quick feedback.

Additionally, I suggest that you have a re-read of the very similar question you asked several years ago - [HERE LINK] and have another read of the thread which Donald referenced to you - [HERE LINK]. There is a lot of both general and specific information in both threads that will benefit.

WW

[dje]

Additionally, I suggest that you have a re-read of the very similar question you asked several years ago

Bill that was about 6 years ago. You must have a "photographic" memory

Dave

[William W]

Dave - I haven't used an A7, the descriptive you gave regarding the viewfinder display change when 'half depress shutter button' was informative additionally, made me think more that the Sony A Series is a very good kit: certainly their lenses are swish, and they make white ones too.

WW

[dje]

Dave - I haven't used an A7, the descriptive you gave regarding the viewfinder display change when 'half depress shutter button' was informative additionally, made me think more that the Sony A Series is a very good kit: certainly their lenses are swish, and they make white ones too.

WW

Yes Bill, I don't know the sales figures but the Sony mirrorless range seems to have been quite a success. I've been happy with mine. There is a fairly extensive range of lenses designed specifically for their E mount (APS-C and FF). The white ones will please some

Dave

[Mingmoos]

Thank you again to everybody for your helpful and interesting answers to my question on flash settings. I now have a better understanding of how flash works and the relationship between ambient light and the action of the flash. My flash is a HVL-F43M by the way and does have TTL. Just one further question, where is the advantage in using high speed sync. Surely using a higher shutter speed will impact on the ambient light captured and also make the flash work harder to achieve correct exposure? I can understand use of high speed sync in a hand-held situation, but is it necessary when using a tripod? James.

[pschlute]

Just one further question, where is the advantage in using high speed sync. Surely using a higher shutter speed will impact on the ambient light captured and also make the flash work harder to achieve correct exposure? I can understand use of high speed sync in a hand-held situation, but is it necessary when using a tripod? James.

HSS will indeed impact on the ambient light, and that is why HSS is often used in bright situations, so the background gets correctly exposed, especially if you are needing to use a very wide aperture.

The flash does have to work differently in HSS mode. The point is all about the maximum sync speed of the cameras shutter (typically 1/180-1/250 range). Above a cameras sync speed there is no one moment in time when the shutter completely exposes the sensor, it becomes a moving slit instead. A conventional flash fires in the order of a number of thousands of a second so you would have only a portion of the sensor exposed by flash. With HSS the flash changes its output to a number of pulses instead of a single one. This means that the sensor can be exposed correctly. But it changes the dynamics too. The pulsing means the total output is weaker, so flash to subject distances get less. It also means that the shutter speed can have an effect on the exposure, unlike when at or below sync. Because HSS is more like continuous light you can get subject blur too.

Best thing is do your research on how these different flash modes work and get out and practice them at home. You may never use them again but will give you a broad basis to build on.

[pschlute]

I can understand use of high speed sync in a hand-held situation, but is it necessary when using a tripod? James.

Here is a good example of why an understanding of the different modes (normal flash versus HSS) will be helpful going forward.

When it comes to lighting your subject with flash (ignore ambient for a moment), you can get more subject movement using HSS and say 1/500, than using 1/60 and normal flash.

The reason being that your flash will be firing in normal mode a lot faster (1/5000 sec ?) than your shutter speed of 1/500 in HSS mode.

[Manfred M]

Thank you again to everybody for your helpful and interesting answers to my question on flash settings. I now have a better understanding of how flash works and the relationship between ambient light and the action of the flash. My flash is a HVL-F43M by the way and does have TTL. Just one further question, where is the advantage in using high speed sync. Surely using a higher shutter speed will impact on the ambient light captured and also make the flash work harder to achieve correct exposure? I can understand use of high speed sync in a hand-held situation, but is it necessary when using a tripod? James.

James - the tripod or handheld has little to do with it as that eliminates one component of movement; the camera. If the subject is moving quickly, especially if you are shooting in a situation where the ambient light makes a significant contribution of the total light making the image. We often use flash in backlit outdoor lighting, so if you have a fast moving subject and you hit it with the 1/1000th (or less) second duration flash, but your shutter speed is 1/200th sec, you will still see motion blur in your image.

Set up HSS and shoot at 1/1000th sec, you can freeze all movement, which may be what you are trying to achieve.

Just to throw something else at you as you are learning flash photography; direct flash (where the flash is sitting on your camera's hot shoe and pointing directly at the subject) is used as little as possible in serious photography. Swiveling the flash so that it bounces off a light surface (bounce flash) or taking the flash off the camera and putting it on a light stand and using a light modifier, like and umbrella, give far better quality light than makes for stronger photographs.

[William W]

. . . where is the advantage in using high speed sync.

HSS is (arguably) mainly used when we want to use Flash as Fill in a bright Ambient situation.

. . . Surely using a higher shutter speed will impact on the ambient light captured and also make the flash work harder to achieve correct exposure?

Yes and yes.

. . . I can understand use of high speed sync in a hand-held situation, but is it necessary when using a tripod? James.

That comment implies that you assume HSS is used to arrest Camera Movement Blur and that as a general assumption is incorrect. A better general assumption is that the use of HSS does NOT, of itself, address Camera Movement Blur.

WW

[Mingmoos]

Thank you to everybody who gave me such valuable advice, I will continue my journey understanding the finer points of flash photography with renewed confidence. James.

[rpcrowe]

Originally Posted by Mingmoos View Post
. . . I can understand use of high speed sync in a hand-held situation, but is it necessary when using a tripod? James.
Bill wrote...
"That comment implies that you assume HSS is used to arrest Camera Movement Blur and that as a general assumption is incorrect. A better general assumption is that the use of HSS does NOT, of itself, address Camera Movement Blur."

I totally agree with Bill! HSS is used when the shutter speed of your camera is shorter than the maximum camera sync speed. If you are shooting in a situation in which the flash provides the vast majority of the exposure - a slower shutter speed will be no problem since the very fast burst of light will freeze any motion (be that camera shake or subject motion)...

However, when ambient light contributes a significant amount to the exposure you "might" need a faster shutter speed to freeze subject motion and or camera shake. Although IBIS or lens stabilization might very well compensate for camera shake - if your camera, lens is so equipped, it will not freeze any subject motion.

My main use for HSS is when I am shooting outdoor portraits using a lens with a very wide aperture to isolate my subject from the background. Shooting at f/1.4 or even f/1.8 in bright sunlight will require a very fast shutter speed even when using your lowest ISO. Unless you use an ND filter, shutter speeds required can exceed 1/4,000 second which makes the use of HSS for fill flash mandatory...

BTW: one thing that I always liked about shooting a Canon DSLR camera is that, when you have HSS selected, the camera will automatically revert to standard sync whenever your shutter speed is at or below the camera's max sync speed and then go back to HSS when that shutter speed is faster than the max camera sync speed. In that, you have the best of two worlds...

[Manfred M]

Of course Richard, the old fashioned solution to shooting at large aperture settings in bright lights is to use ND filters to cut down the ambient light and stick with normal flash. Not necessarily great for freezing motion, but something I used in the film days too.