Flash power output in E-TTL

[kuchars22]

Hi everyone,

First time here! I have a 430ex on a 450d, and I am learning about all the features of flash photography. I "think" I understand the concept of E-TTL and how various technologies within this helps make a more acceptable image. To further understand flash photography, I would very much like to start shooting with the flash in Manual mode. I have found, through experimentation, that I can dial in to a more precise flash output in manual mode. I have learnt how each stop in reduction or increase in flash power affects the final image, but I'm eager to understand it more.

Here are my questions:

The 430ex has a power range from full power (1/1) to minimal power (1/64) in manual mode.

1) In E-TTL mode, does it select this same power range, anywhere between 1/1 and 1/64, to obtain the "correct exposure"?

2) I shoot in Av mode a lot, and have the shutter speed set to Auto (rather than fixed to 1/200) to pick up ambient lighting, then normally adjust the FEC accordingly for fill-flash. When compensating on the flash in E-TTL, are you actually adjusting the flash power output from the setting that E-TTL has recommended? So say E-TTL recommends a power of 1/32, but setting FEC to -1 stop - does the flash output reduce to 1/64, is this how it works? In E-TTL, there is no way of telling what flash output it has used, before or after a shot?

3) I have also experimented by adjusting ISO settings. Does the ISO setting actually affect the flash output, or does it affect the camera's sensitivity, thereby affecting how the flash affects the final exposure?

4) I have a church event this Sunday (Baptism), the church has a lot of incadescent lighting, and the children in the shots will be very young so a lot of movement. If I want to get a nice shot showing the ambient background and freezing the foreground subjects, am I asking too much from the camera/flash? As far as I understand, to produce enough light for the background, the shutter speed will have to be low enough to capture this, but will affect any fast movement from the children? Is there no such a method other than balancing out the ambient exposure with enough speed for the subjects? Would it be better to set the flash to 1st curtain sync so it flashes at the beginning of the exposure? I will either be using a 50mm f1.8 or 28mm f2.8.

Thanks for reading!

[tim]

Welcome to POTN :)

1) In ETTL the flash can probably go lower, and in smaller graduations.
2) Yes, you're adjusting from the metered value. I don't think you can tell what power was used.
3) ISO affects the sensor sensitivity. Assuming no ambient light you'll get the same exposure with ISO400/F4 as ISO800 F5.6 (one stop difference for each setting). Shutter speed controls only the ambient exposure, within the sync speed.
4) Manual on the camera, metered one stop below ambient light. Flash on ETTL, FEC+1. Gel your flash to match the ambient color temperature if you want a really good image - a local camera store will sell gels. Something like ISO800 1/50th F2.8 (or whatever you can get) may be a good starting point. When the flash fires is irrelevant, always use 1st curtain unless you're certain you need 2nd. In five years of photography I never have.

[kuchars22]

Thanks for your response. Why would I go -1 stop from the metered sensor, and then +1 stop on the flash? Would this just cancel itself out and produce the same exposure?

[tim]

No, flash exposure controls the foreground/main subject, camera exposure controls background exposure. Say you shot ISO100 F9 1/200th in a dark church, FEC+1, the main subject would be bright but the background would be pretty much black. At ISO800 F2.8 1/30th the background would be way more visible.

If you set your camera exposure (for the background) one stop below the proper exposure the background will be visible, but not overwhelming. The flash will light the main subject and make them stand out. Maybe you don't want to be a stop under, maybe you want both to be good. Maybe you want it two stops under. Just play and make an image you like :)

[kuchars22]

I see now!

So let's recap:

If I have the flash on E-TTL, it will perform as fill-flash, and I can control the output by FEC to suit my taste for foreground, whilst controlling background lighting with the camera controls, either using M or Av.

But if I decide to go manual on the flash, I should treat the background lighting in the same way as just mentioned, adjusting the camera controls as necessary, using Av or Manual, and again, adjust the flash for foreground but this time manually setting the output between 1/64 to 1/1 to suit my taste?

If this is the case, I don't really need to use manual setting on the flash unless the situation is consistent, like in a studio, or I want to keep consistent results, or E-TTL isn't providing me with the results?

I'm interested in your point about E-TTL, where it may use less power than manual settings. I will do a bit more research and let you know what I find.

[Dermit]

Another thing to keep in mind when mixing light sources (Flash with ambient) is that your white balance is going to be whacky. If you balance for flash and your background is lit by florescent then the background will be greenish. One way to solve this so they are both balanced is to add a greenish filter to your flash and balance for florescent.

[Titus213]

I'd be careful with Av in a flash environment. Av will attempt to produce a proper exposure for the available light and could result in a shutter speed too low to safely hold.

For my shooting a flash = manual mode on the camera. Flash can be in manual or ETTL.

[kuchars22]

Another thing to keep in mind when mixing light sources (Flash with ambient) is that your white balance is going to be whacky. If you balance for flash and your background is lit by florescent then the background will be greenish. One way to solve this so they are both balanced is to add a greenish filter to your flash and balance for florescent.

Good point, didn't think of that. Just been reading about gel filters. Most lighting indoors will be standard household bulbs, and when setting the camera to tungsten, it gives me a warm look, sometimes feels too artificial. But I can sometimes cool it down a bit by stopping down or increasing shutter speed a little. Flash may give a cooler result to the foreground subject, and I guess this is where I should be using filters to cool it down a bit? In this situation, what colour will I need to balance the flash white balance to the ambient, as a starting point?

[gonzogolf]

But I can sometimes cool it down a bit by stopping down or increasing shutter speed a little. Flash may give a cooler result to the foreground subject, and I guess this is where I should be using filters to cool it down a bit? In this situation, what colour will I need to balance the flash white balance to the ambient, as a starting point?

First don't alter your exposure to get a color match, there are other ways to change color than messing with your exposure. In the case of household bulbs, they are tungsten so you would set your white balance to tungsten, then add a cto gel to balance. Tungsten light is orange so the CTO (Color Temperature Orange) gel would match the light in the room, and the white balance adjustment lets the camera see it as white...

[tim]

I see now!

So let's recap:

If I have the flash on E-TTL, it will perform as fill-flash, and I can control the output by FEC to suit my taste for foreground, whilst controlling background lighting with the camera controls, either using M or Av.

But if I decide to go manual on the flash, I should treat the background lighting in the same way as just mentioned, adjusting the camera controls as necessary, using Av or Manual, and again, adjust the flash for foreground but this time manually setting the output between 1/64 to 1/1 to suit my taste?

If this is the case, I don't really need to use manual setting on the flash unless the situation is consistent, like in a studio, or I want to keep consistent results, or E-TTL isn't providing me with the results?

I'm interested in your point about E-TTL, where it may use less power than manual settings. I will do a bit more research and let you know what I find.

You've pretty much got it! Except the flash in ETTL can be the main light if the camera's in manual mode. In Av the flash is generally fill. ETTL has more control over the flash power than the buttons give you.

There's generally not a lot of need/use for manual flash, unless you're using them off camera. I only ever use manual flash with off camera lighting.

[kuchars22]

You've pretty much got it! Except the flash in ETTL can be the main light if the camera's in manual mode. In Av the flash is generally fill. ETTL has more control over the flash power than the buttons give you.

There's generally not a lot of need/use for manual flash, unless you're using them off camera. I only ever use manual flash with off camera lighting.

I've been experimenting with my son's hobby horse as a subject, stood up in the middle of the room, allowing plenty of space behind, and dimmed the lights down a bit, all to try and give it a church style atmosphere.

I have left the camera on Manual an left the lens on at f/1.8 at ISO 1600 and this has given me about 1/50sec without flash. The results are good, but could do with a few more stops of shutter speed to reduce any shake. With the flash in E-TTL, I found that I was able to push the shutter speed a little faster to reduce shake, but at the same time, not affect the ambient lighting too much as if flash wasn't on. I guess this is the result of the flash "spilling" over to the background? I don't know how high the ceilings are, but will prefer to bounce it if I could. I have a Sto-Fen diffuser on my flash too.

For more DOP, I've set to around f/5.6 but I definitely need flash at that point (about -1 to -2 FEC). I then tried my 17-85mm IS USM, but this is staying at home, as this was pretty useless in comparison to my "bargain bin" 50mm f/1.8!!

From these tests, I have learnt a lot about Manual camera mode and I'm hooked on it! There is a lot more involvement which is very satisfying when you get the results you want...took me a while to figure out why I couldn't apply exp. compensation in Manual!

BTW I couldn't find any difference betwen manual and Av when the flash is in E-TTL mode, as you suggested. Does E-TTL automatically adjust output for foreground due to evaluative metering in Av mode?

Just one more question: whilst I was experimenting, I set the camera to custom WB using a grey card. When using this without flash it was bit cool, and too orangy when set to Tungsten. However, when I use flash under custom WB, it was more blue than without flash, but perfect under Tungsten. Is the flash introducing more blue to the image, and is this an example of a situation when I should be using correction filters, as Gonzogolf said?

Thanks again

[tim]

In Av mode the flash isn't quite as bright, but in practice you might not notice. Search for NEVAC, I think it has something to do with it.

The flash is white, and AWB works fine most of the time. If you shoot RAW you'll be able to fix any white balance problems later. What you can't fix is a mix of white light from the flash and tungsten light from the room lights. For that gel your flash and use a tungsten white balance, still in RAW.

btw out of perhaps 50 church weddings i've used flash once. I just prefer not to. I'll use ISO3200 F2.8 1/50th before I use flash, and now with the 7D I think ISO6400 or even 12800 will be preferable to flash.

[kuchars22]

In Av mode the flash isn't quite as bright, but in practice you might not notice. Search for NEVAC, I think it has something to do with it.

The flash is white, and AWB works fine most of the time. If you shoot RAW you'll be able to fix any white balance problems later. What you can't fix is a mix of white light from the flash and tungsten light from the room lights. For that gel your flash and use a tungsten white balance, still in RAW.

btw out of perhaps 50 church weddings i've used flash once. I just prefer not to. I'll use ISO3200 F2.8 1/50th before I use flash, and now with the 7D I think ISO6400 or even 12800 will be preferable to flash.

Wow! I wish I could go up to ISO 3200! Do you know if the High ISO Noise Reduction works well or not?

[tim]

What high iso noise reduction? I don't really bother reducing noise, by the time you reduce the image size down to whatever you print it's usually not visible.

[egordon99]

Wow! I wish I could go up to ISO 3200!

Shoot raw at ISO1600, set EC to -1, in your raw processor, increase the exposure by one stop. Voila! ISO3200 ;)

[MT Stringer]

I have a church event this Sunday (Baptism), the church has a lot of incadescent lighting, and the children in the shots will be very young so a lot of movement.

Questions...
1) Is flash allowed?
2) Will there be enough ambient light to shoot without a flash?
3) Where will you be? Close or out in the audience?

Reason I ask, here is a heavily cropped image of my granddaughter taken from my seat in the tenth row in a junior high auditorium.
Hope this helps.
Mike
1D MK III, 135L at f/2.8, ISO 1250 - 1600, AV mode

[kuchars22]

Questions...
1) Is flash allowed?
2) Will there be enough ambient light to shoot without a flash?
3) Where will you be? Close or out in the audience?

Reason I ask, here is a heavily cropped image of my granddaughter taken from my seat in the tenth row in a junior high auditorium.
Hope this helps.
Mike
1D MK III, 135L at f/2.8, ISO 1250 - 1600, AV mode

I don't know if flash is allowed and the level of lighting, which is why I dimmed the lights down low enough that most church's won't have. That way, if I can handle this situation, I should handle any. I did attend a wedding there a few years back and I've been looking at some pictures from my point and shoot, just looks like a load of incandescent lights as I can see low level chandeliers.

It's a small ceremony and I will be very close, will only be about 2 rows from the front, but will be distancing myself at times to get groups shots with my 50mm f/1.8, or I might use my 28mm f/2.8 if light is in my favour, so I don't need to stand outside the church to get the group shots!

[kuchars22]

Shoot raw at ISO1600, set EC to -1, in your raw processor, increase the exposure by one stop. Voila! ISO3200 ;)


Interesting technique, but can you explain what is happening here? In the 450d, there is a custom function to set "High ISO noise reduction" on or off. Couldn't tell the difference when shooting RAW in both cases, and close up in DPP showed very similar results, and affects from NR was also the same. May be it is more suited to JPEGs?

[letterperfectink]

Hi everyone,

First time here! I have a 430ex on a 450d, and I am learning about all the features of flash photography. I "think" I understand the concept of E-TTL and how various technologies within this helps make a more acceptable image. To further understand flash photography, I would very much like to start shooting with the flash in Manual mode. I have found, through experimentation, that I can dial in to a more precise flash output in manual mode. I have learnt how each stop in reduction or increase in flash power affects the final image, but I'm eager to understand it more.

Here are my questions:

The 430ex has a power range from full power (1/1) to minimal power (1/64) in manual mode.

1) In E-TTL mode, does it select this same power range, anywhere between 1/1 and 1/64, to obtain the "correct exposure"?

2) I shoot in Av mode a lot, and have the shutter speed set to Auto (rather than fixed to 1/200) to pick up ambient lighting, then normally adjust the FEC accordingly for fill-flash. When compensating on the flash in E-TTL, are you actually adjusting the flash power output from the setting that E-TTL has recommended? So say E-TTL recommends a power of 1/32, but setting FEC to -1 stop - does the flash output reduce to 1/64, is this how it works? In E-TTL, there is no way of telling what flash output it has used, before or after a shot?

3) I have also experimented by adjusting ISO settings. Does the ISO setting actually affect the flash output, or does it affect the camera's sensitivity, thereby affecting how the flash affects the final exposure?

4) I have a church event this Sunday (Baptism), the church has a lot of incadescent lighting, and the children in the shots will be very young so a lot of movement. If I want to get a nice shot showing the ambient background and freezing the foreground subjects, am I asking too much from the camera/flash? As far as I understand, to produce enough light for the background, the shutter speed will have to be low enough to capture this, but will affect any fast movement from the children? Is there no such a method other than balancing out the ambient exposure with enough speed for the subjects? Would it be better to set the flash to 1st curtain sync so it flashes at the beginning of the exposure? I will either be using a 50mm f1.8 or 28mm f2.8.

Thanks for reading!


I would love to know how you experimented and learned so much about your flash! I'm very impressed with your questions! I would love any tips you may have! When I use E-TTL It drives me crazy trying not to overexpose faces in my outdoor portraits. I'm constantly trying different metering modes, using FEL & adjusting Flash Compensation. I wish I new of a way to better provide fill flash with a constant result every time :)

Thanks!

Christie
(Canon 40D, 430EX II, Tamron 28-75mm f/2.8)

P.S. by the way I'm pretty new to the forum as well.

[egordon99]

I wish I new of a way to better provide fill flash with a constant result every time :)

Thanks!



Welcome to the forums! If you want consistent results, look into using Manual mode on the flash, where YOU set the flash power (1/1, 1/2, 1/4,1/8,etc....)

I'm a fan of ETTL, but I'm starting to get used to slowing down a bit and using manual flash.

My biggest peeve of ETTL is that there is no way to determine what power ETTL decided to use for a particular shot. It would be the same as if you were shooting in AUTO and had NO way to figure out the ISO/f-stop/shutter speed of a particular shot.

[apersson850]

Flash on faces outdoors hardly ever work in E-TTL II, according to my experience. The camera will almost always try to make the flash illuminate something more than the face, that that "something" typically requires more light than the face can take. Hence, overexposure.

I use FEL directed towards the face. That's usually good, sometimes combined with some negative FEC, since faces are usually better slightly too dark than overexposed.

This also has a lot to do with your personal preferences.

I agree with Tim on that 2nd curtain sync is in almost every case nothing you need. Some people think they need it always, but don't know that with shutter speeds of 1/30 s and shorter, the camera will use 1st curtain sync, regardless of what you set it to. So they are happy with their 2nd curtain sync images. When I made the bet that one of these guys wouldn't see the difference if he set it to 1st curtain, he was very surprised to see I was right. He shot at 1/125 s...

[kuchars22]

I would love to know how you experimented and learned so much about your flash! I'm very impressed with your questions! I would love any tips you may have! When I use E-TTL It drives me crazy trying not to overexpose faces in my outdoor portraits. I'm constantly trying different metering modes, using FEL & adjusting Flash Compensation. I wish I new of a way to better provide fill flash with a constant result every time :)

Thanks!

Christie
(Canon 40D, 430EX II, Tamron 28-75mm f/2.8)

P.S. by the way I'm pretty new to the forum as well.

I use my son's hobby horse set in the middle of the room, and just blast several shots one after the other with different settings, until I can understand the relationships between different stops.

Well, the baptism came and went, and I took some great pictures (posting soon), but to my surprise, the church (recently refurbished since I last went there) had PLENTY of natural daylight passing through the new windows! I didn't use one ounce of flash! Here are my lessons learnt:

1) @Use the lowest ISO necessary. At the beginning, I ramped up the ISO to 1600 to ensure good hand-holding speeds of around 1/600 or greater, and also following some advice here on the forums. However, this was often too high, with my 50mm f1.8 and bright light entering the church, and got higher shutter speeds than necessary. This resulted in some pics having too much noise. Though this was superbly resolved using Ninja Noise, the image is "compressed" and would have been better reducing the ISO by at least 800 or 400 to retain sharpness, and shutter speeds would have still been acceptable.

2) Bracket your shots. A lot of my shots where over and underexposing like crazy throughout the ceremony! I met my brother an hour earlier to learn that he was wearing a black suit. When we got to the church, the priest was obviously wearing white and this confused the hell out of my camera's metering system! You have to work fast to view the image and compensate as required otherwise you will miss the shot, which I did on many occassions. I didn't bracket, in fact, I've never used ever used it before, but in hindsight, I would have done usesd this feature.

3) Beware of Depth-of-field. I am addicted to f2.8 or less, and opens up a new world of low-light photography, but I often get too distracted with the capabilities and ignore DOP. In some of my group pics, foreground or background people were out of focus. Higher apertures should be respected and should never forget all other variables that it affects (true for all other variables in a camera).

Anyway, after all this I didn't use flash, but I have learnt hell of a lot - I've got some free gel samples from Lee, made my own holder and experimented with this to great success. I'm now eagerly awaiting the next church ceremony so I can test my skills.

Here's one more question - not related to this topic in particular, but I will also put this in the correct forum:

I'm looking into off-camera flash work, and I have still yet to invest in any remote, radio or cord solution. Some systems carry E-TTL information to the remote flash, but I was wondering how E-TTL works in an off-camera situation? Is it only useful for when the flash is in directly parallel line to the lens, as in a flash bracket? The way I see it, if a flash gun is a few metres away pointing at a subject from a different angle than your camera, the flash cannot determine the distance and angle in relation to the camera sensor or determine the AF points to read the correct exposure. In other words, it is no longer measuring at the same point from the camera.

Thanks

[ollyb]

Just read this thread and am really impressed with decent questions and helpful answers. I feel I've learnt a lot (despite not owning an external flash unit at all....)

[Rafromak]

Interesting technique, but can you explain what is happening here? In the 450d, there is a custom function to set "High ISO noise reduction" on or off. Couldn't tell the difference when shooting RAW in both cases, and close up in DPP showed very similar results, and affects from NR was also the same. May be it is more suited to JPEGs?

In-camera noise reduction doubles the amount of time the camera takes between photos. What you can do is to reduce the digital noise with Noise Ninja, Neat Image, and other applications.

By the way, somewhere in this forum there are quite a lot of examples of "party in low light" shots taken by a forum member. Some of his outstanding photos were taken at 1,600 ISO (I don't remember the lens apertures), and the flash on E-TTL. The high ISO was to help the camera with ambient light, and the flash to illuminate the subject (s).

Here you go:
http://photography-on-the.net/forum/showthread.php?t=369787&highlight=party+shots+with+flash

[kuchars22]

Yeah, they are great shots. Ninja Noise is great but need to use sparingly as it can lose definition if used too much. I'm not afraid to use higher ISO's now, know that I could reduce it afterwards. However, I also learnt that noise it more prominent in darker areas or in shadows when bumped up. High ISO in brightly lit scenes don't show up as much, I guess this is what is meant by "exposing to the right" [of the histogram] so as to retain shadow areas to avoid noise when increasing post exposure.