fill flash and sync flash

REPOSTED FROM BEGINNER FORUM

I'm trying to understand how my camera (Nikon D40) treats flash. The answers are not in the manual, to head off any suggestions to look on pages 34-35...

I normally shoot in Aperture mode and select the aperture based on the DoF that I want.

When I select fill flash, my shutter speed is fixed at 1/60. This is consistent with Nikon's online explanation.

I fired off a series of shots (somewhat backlit) from wide open to f/16, and predictably the backgrounds varied from overexposed to underexposed. The flashed subject stayed relatively correctly exposed, at least to my novice eyes. (I used the 50mm 1.4D)

When I switched to slow sync, the shutter speed varies to maintain a correct background exposure. The flashed subject, however, was overexposed (although easily corrected with flash compensation). I didn't repeat my previous experiment through several f-stops, so I don't know if I will have to continuously vary the flash compensation.

The fill flash behavior seems like a weakness; I would have thought that the shutter speed should still vary with aperture, perhaps moving down a third or two to compensate for the extra light from the flash. Instead, any picture I take at a large aperture will be overexposed due to the fixed shutter speed (and vice versa for small apertures).

How should I beat this? Am I having trouble understanding because I'm misapplying fill flash - i.e., it's only used at medium to small apertures when foreground and background should both be sharp? Why does fill flash fix the shutter speed? Does the flash in slow sync mode properly adjust output based on foreground concerns while the camera autoexposure handles the background? Should I give up and stick to daylight shots with no backlighting?

The slow sync appears to work fine for me (D90) but I'm not so keen on flash photos anyway.

You probably will get more replies if you post some pictures to illustrate your point.

Al

You are in the wrong mode. A mode ihas limited flash options compared to M mode. It is limited by that 1/60th second setting hard coded into A mode.

Put the camera in M mode and try your experiments again.

--
Catallaxy

Were you using a external flash or the onboard flash?

Why were you running tests with a back-lit subject? I have good luck with the SB-600 in TTL-BL mode with back-lit subjects.

Thanks for the responses. I'm a bit scared to try Manual, but that sounds like the most logical step.

Pics were taken with onboard flash, and I took them this way just to experiment with properly using fill flash. I wanted a difficult exposure to see the limits of the flash. I can't post the test pics without being skinned alive by my camera-shy fiancee, but I will take a new set if I have more questions after trying M mode.

In Manual mode, will the flash automatically meter even though I am manually setting aperture and shutter speed? Or will I need to adjust flash exposure value manually as well?

tamunick wrote:
[snip]

tamunick said:

In Manual mode, will the flash automatically meter even though I am manually setting aperture and shutter speed? Or will I need to adjust flash exposure value manually as well?

Click to expand...

The camera can automatically meter for the flash output while you've set the shutter and aperture manually. Just leave the flash in TTL mode.

larsbc

Catallaxy said:

You are in the wrong mode. A mode ihas limited flash options compared to M mode. It is limited by that 1/60th second setting hard coded into A mode.

Put the camera in M mode and try your experiments again.

Click to expand...

But if the OP is shooting in slow sync mode, the shutter speed will no longer be locked at 1/60 sec, even if he's in Aperture priority mode.

It'd help to see example photos of the problem, because it may have something to do with the metering being fooled by something in the scene.

larsbc

tamunick said:

Pics were taken with onboard flash, and I took them this way just to experiment with properly using fill flash. I wanted a difficult exposure to see the limits of the flash.

Click to expand...

You would be surprised how many people show up with questions the day of a big event (or the day after) with questions and no experience. You went about it the right way by practicing in a situation where the results were not super critical. I don't know that I would recommend starting with a difficult situation, but at least you understood that it would be difficult.

In a back-lit situation, use aperture and shutter speed to freeze motion, control depth of field, and control background exposure. Use flash compensation to adjust exposure of your subject. The on-board flash has a limited range and you can raise the ISO to extend the flash range...with corresponding adjustments to background exposure.

As I mentioned before, TTL-BL with an SB-600 works great and is quite easy. For my money, an external flash should be one of your first purchases after getting your camera.

Along with practice with the suggestions made here, here is a site that I found extremely helpful

http://www.planetneil.com/tangents/flash-photography-techniques/

The beauty and the wonder of flash photography is that you put your flash in TTL mode, put your camera in manual mode, and magically the flash puts out the exact amount of light to expose your picture perfectly every time.

So for beginners here's the important points:
Put you camera in manual mode DON'T be afraid - it's the right thing to do.
Choose shutter speed like 1/80 and fstop 6.3 or whatever you like

Don't look at the meter. It will tell you often you are way underexposing. Don't pay attention to it.
Did I say ingore the meter?

Shoot - and exposure will be perfect every time. So you don't have to worry about exposure.
--
Larry

tamunick said:

REPOSTED FROM BEGINNER FORUM

I'm trying to understand how my camera (Nikon D40) treats flash. The answers are not in the manual, to head off any suggestions to look on pages 34-35...

I normally shoot in Aperture mode and select the aperture based on the DoF that I want.

When I select fill flash, my shutter speed is fixed at 1/60. This is consistent with Nikon's online explanation.

Click to expand...

The 1/60 second (a limit - minimum shutter speed with flash) is only true of flash indoors (in camera A or P mode), when the ambient light is more dim than 1/60 second. The 1/60 is not "correct", it is merely a limit. This dim room is the reason you are using flash. In that more dim situation, the camera assumes you do not need a 1/8 second shutter speed, if you are using flash. It sets this 1/60 second minumum limit as being reasonable. Take the flash outdoors, as fill flash in bright sun, and you will see much faster shutter speeds, equal to ambient, when there is some ambient.

tamunick said:

I fired off a series of shots (somewhat backlit) from wide open to f/16, and predictably the backgrounds varied from overexposed to underexposed. The flashed subject stayed relatively correctly exposed, at least to my novice eyes. (I used the 50mm 1.4D)

Click to expand...

Aperture simply varies the demand for TTL flash power. TTL flash adjusts that flash power level as it determines is needed (if it can). The flash needs and uses 16 times more power at f/16 than at f/4 (if it has that much power available). The recycle time becomes long at high power, and quick and immediate at low power level, so you know about where you are. Were you watching the Ready light warning of insufficient power? Read and understand SB-600 page 29, SB-800 page 33, or SB-900 page D-4, about the insufficient power warning. This is a MAJOR tool.

tamunick said:

When I switched to slow sync, the shutter speed varies to maintain a correct background exposure. The flashed subject, however, was overexposed (although easily corrected with flash compensation). I didn't repeat my previous experiment through several f-stops, so I don't know if I will have to continuously vary the flash compensation.

Click to expand...

Slow sync simply ignores the 1/60 second minimum shutter speed limit with flash. Then you get actual ambient metering, slow as it may be. The difference in TTL and TTL BL flash mode is that TTL assumes flash is sole light source. If both TTL and ambient are metered correctly, the flash is 1 stop overexposed from both (unless you apply suitable flash compensation). TTL BL will try to reduce the flash level to prevent that, to match ambient.

tamunick said:

The fill flash behavior seems like a weakness; I would have thought that the shutter speed should still vary with aperture, perhaps moving down a third or two to compensate for the extra light from the flash. Instead, any picture I take at a large aperture will be overexposed due to the fixed shutter speed (and vice versa for small apertures).

Click to expand...

Flash is totally unaffected by shutter speed. The flash exposure is not dependent on which shutter speed you use. The flash is much faster than any shutter speed... the shutter simply has to be open to let the flash come through.

Flash is very different than continuous ambient. Be aware of some basics:

See http://www.scantips.com/lights/flashbasics4.html

Flash is very different, but still easy, if you know.

tamunick said:

I normally shoot in Aperture mode and select the aperture based on the DoF that I want.

When I select fill flash, my shutter speed is fixed at 1/60. This is consistent with Nikon's online explanation.

I fired off a series of shots (somewhat backlit) from wide open to f/16, and predictably the backgrounds varied from overexposed to underexposed. The flashed subject stayed relatively correctly exposed, at least to my novice eyes. (I used the 50mm 1.4D)

When I switched to slow sync, the shutter speed varies to maintain a correct background exposure. The flashed subject, however, was overexposed (although easily corrected with flash compensation). I didn't repeat my previous experiment through several f-stops, so I don't know if I will have to continuously vary the flash compensation.

The fill flash behavior seems like a weakness; I would have thought that the shutter speed should still vary with aperture, perhaps moving down a third or two to compensate for the extra light from the flash. Instead, any picture I take at a large aperture will be overexposed due to the fixed shutter speed (and vice versa for small apertures).

Click to expand...

I don't have a D40. I use a D50, but I think the flash options are probably the same:

When you set A mode (aperture priority) the shutter speed is fixed at 1/60 sec. The camera will adjust the output of the flash to expose the subject correctly. The background will be exposed according to your set f-stop at 1/60 sec. You may have noticed that the light meter reading reflects the exposure of the background rather than how the subject is lit by the flash.

When in slow sync, the camera sets exposure for the overall scene and the flash fires at some level of intensity (based upon the focus distance, I think.) As you found, you can adjust the intensity of the flash to get the look you like.

Although I use A mode almost exclusively for general picture taking, I have started using manual mode more often when I use flash. It is not difficult to set the aperture and then dial in the shutter speed according to the meter reading in the finder. Fill flash often looks pretty good with flash compensation set to -0.7 or -1.0 ev although you might prefer even less flash for a more natural look.

As I became better at using flash, I opted for an external unit - an SB-600. It offers many benefits over the built-in flash and there is a button on the back that can be used to set flash compensation, which to me is more convenient than adjusting compensation on the camera.

As stated in another reply, I must congratulate you on taking the time and effort to figure this out. Many people simply state that they hate flash - I have found it to be a very useful tool, but one that has to be learned to be truly effective.

--
pschatz100
It's not how many pixels you have... but how you use them.

My experience is with a D70, which is an earlier camera, but from the replies, I think it's fairly similar. Using M mode allows the best use of the various flash modes, especially fill flash or BL (balanced lighting). Also, the Nikon metering system makes using the M mode fairly easy.

Ignore the exposure compensation button, or rather, set it to no compensation. Then put the camera in M mode. When you set the aperture and shutter speed, the exposure indicator in the bottom of the viewfinder shows whether the shot is metering over or under exposure.

There are some warnings here. There is a limit to how fast the shutter speed can be to work with the flash. You can check your manual for your camera to find this. Once you've set the aperture and shutter speed, try a shot. Then, very important, check the histogram. If the histogram shows that you're under or over exposed, adjust the aperture or the shutter speed and try again.

My D70 is usually pretty close when the metering indicator is centered. Once you have the proper exposure, the fill flash can do its job properly. I usually set the fill flash to -1.5 or -2. After all, I'm just adding a little fill light to the shadows.

Now, for flash lit shots, not fill flash, but where there isn't enough light to shoot without flash, things will be different, but this was about fill flash.

-Raf

tamunick said:

Thanks for the responses. I'm a bit scared to try Manual, but that sounds like the most logical step.

Pics were taken with onboard flash, and I took them this way just to experiment with properly using fill flash. I wanted a difficult exposure to see the limits of the flash. I can't post the test pics without being skinned alive by my camera-shy fiancee, but I will take a new set if I have more questions after trying M mode.

In Manual mode, will the flash automatically meter even though I am manually setting aperture and shutter speed? Or will I need to adjust flash exposure value manually as well?

Click to expand...

Hi,

IMO it is best to use M-mode + i-TTL mode + AUTO-ISO with flash , I use a D40 with the SB400/900 with following settings :

• TTL flash mode
• matrix metering
• M-mode ( i choose Shutterspeed and Aperture myself , eg S = 1/100

sec to freese motion, A = high enough for needed DOF )

• base iso to eg 400 ( capture some ambient light )
• set auto iso ON -> set max ISO ( eg 800 or 1600 ).
• use a bounce panel if you cant bounce on ceiling or wall

M mode : This way i can control shutterspeed and aperture, the camera
selects the iso and flash output.

If you select matrix or average metering , the camera will try to
balance ambient light in the background and flash output (
TTL-Balanced ) . If the camera cannot balance the light it will
automatically choose TTL-standard and will use base iso and will
regulate flash output to have correct exposure of the subject you
focused on.

If you select spot metering, the camera wil always use TTL-standard
mode and will not try to balance ambient light in the background with
flash light on the main subject.

You can also dial in flash exp. compensation if needed.

An example shot with above mentioned settings

auto iso choose 800 f6.3 1/100sec



following websites give more advanced information, at leadt interesting to read :

http://www.planetneil.com/tangents/flash-photography-techniques/
http://strobist.blogspot.com/2006/03/lighting-101.html

--
Greetings,
Marc

ps : some interesting tutorial websites :

http://www.ronbigelow.com/articles/articles.htm
http://www.cambridgeincolour.com/tutorials.htm
http://www.luminous-landscape.com/tutorials/
http://www.normankoren.com/sitemap.html



my photos (under construction):
http://www.flickr.com/photos/mrbr03/

Keep in mind in TTL that there are two completely different metering systems: the flash and the camera. The camera's meter will expose the background and the flash's meter will expose the subject. Varying the shutter will not affect the subject's exposure, since the subject is lit almost totally by the flash, only aperture and the power of the flash matter.

Seems so many here are using auto iso with flash. I'm not convinced yet this is best. I like to tell the camera my iso for flash shots - not let the camera decide the iso. Can I hear your logic for using auto iso with flash.
--
Larry

lmpmd said:

Seems so many here are using auto iso with flash. I'm not convinced yet this is best. I like to tell the camera my iso for flash shots - not let the camera decide the iso. Can I hear your logic for using auto iso with flash.
--
Larry

Click to expand...

Hi,

IMO when using flash with M mode and auto-iso ( and selecting base iso 400 and max iso 800 or higer ), the system will use min. iso ( max IQ ) possible. This is what i would do manually to, so the camera makes me save time.

--
Greetings,
Marc

ps : some interesting tutorial websites :

http://www.ronbigelow.com/articles/articles.htm
http://www.cambridgeincolour.com/tutorials.htm
http://www.luminous-landscape.com/tutorials/
http://www.normankoren.com/sitemap.html



my photos (under construction):
http://www.flickr.com/photos/mrbr03/

I have written a series of blogs on the Nikon flash that cover your questions (and a lot more), and I invite you to read them in order starting here:

http://nikonclspracticalguide.blogspot.com/2008/01/nikon-flash-two-separate-metering.html

Be sure to read the Q&A after each post. I haven't captured all that info back in the main blogs yet.

Let me know if you have more questions.

--
Russ MacDonald
http://www.russmacdonaldphotos.com/
http://nikonclspracticalguide.blogspot.com/

lmpmd wrote:
Can I hear your logic for using auto iso with flash.

lmpmd said:

--

Click to expand...

I tried it. It works. End of story.

I've been reading through these blogs, and I wanted to say thanks. They did a great job of outlining the differences between modes. I thought I was getting a lot of contradictory information from posters, but it turns out that most were still correct; thanks to the blog, I understand a lot better why such contradictory answers are all correct.

Thanks!

Like you, I have a D50 and SB600. I avoid flash as much as possible because I'm just not comfortable with it. I think you're saying that you use M mode with TTL-BL for fill flash, TTL for regular flash. But can you tell me your other settings? ISO, Metering mode, etc.? What do you set flash to in the camera's menu? Thanks in advance for your help.
Ellen