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Archive 2005 · FLASH 101

discreet
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p.1 #1 · FLASH 101

Hi, i noticed that a lot of people out there have a lot of hesitation about using flash in low light conditions. They dont like the" deer in the headlamps" look. I hope this small tutorial will clear up some question newbies have.

***I will use an example of a teddy bear in a low lit room. A very typical kind of shoot which a lot of people shoot***

Flash photography is very different from normal photography but a lot of people shoot it the same way. When mastered, it basically gives much more flexibility as photographer as you can now control the light in addition to aperature/shutter/ISO

Okay the basics. In normal available light photography, usually the light entering the camera is constant over the shutter speed (for example if you shoot at 1/25 sec, the intensity of light entering the camera is pretty constant during that interval) For flash photography, the light is not constant if you chose a slow shutter speed. Flash last only a fraction of a second (maybe 1/4000 secs?) and if you using it in a low light situation, it will overpower all the other light sources in the room. So if you are shooting 1/25 sec, the flash only last for 1/4000s and then fades away and then the rest of the ambient light enter the camera for the remaining 1/2 sec.

So, another characteristics of the small light flashes we have is that they are not that powerful and do not have infinite range. If you are standing in the grand canyon at 7 pm, your flash which run on 4 AA battteries will not light the entire grand canyon. Flashes have limited range. What this means is that in a typical "people in dim room" shot, your flash is only going to cover the foreground (the people you are shooting) and not the background (the rest of the room).

So what does all mean

with flash photographer, you have the ability to selective choose how bright/dark the foreground and the background is. Unlike normal available light photography ( with the exception of graduated NDs), there is no way of selectively underexposing/overexposing your foreground/background.

Confused??

Okay, let see some pictures (all on tripod)

Picture 1:

http://marcusgho.com/photogallery/galleries/Untitled%20And%20Unsorted/Flash%20tutorial/No%20flash%20ISO%20400%2C1%3A5%20.JPG

Flash: None
ISO: 400
Aperature: 4.0
Shutter: 1/5 seconds
focal length: 40mm

Comments:
The shutter speed is too slow to hand-hold and if i was not using a tripod, there will be motion blur. Notice that even at ISO 400, the shutter speed is not very fast. At ISO 3200, it will be be only 1/60 seconds. Okay, you can use a lens with a wide aperature (f1.4L) but that is not the point here.

Conclusion: Unless you have a fast lens, this scene is pretty hard to shoot. Fast lens might improve performance but they are expensive and have low DOF which might lead to out of focus shots if you are not careful. Also they are usually primes and if you like zooms... the fastest you can go is f2.8 which is only 1 stop

Picture 2,3,4
Okay... I turned on my 420EX flash and fired 3 shots in Manual mode. Dont worry, in flash photographer, manual mode is actually the most easiest way to shoot.
Settings:
Flash: None
ISO: 100, 400, 3200
Aperature: 4.0
Shutter: 1/125 seconds
focal length: 40mm

ISO 100

http://marcusgho.com/photogallery/galleries/Untitled%20And%20Unsorted/Flash%20tutorial/420%20ISO%200100.JPG

ISO 400

http://marcusgho.com/photogallery/galleries/Untitled%20And%20Unsorted/Flash%20tutorial/420%20ISO%200400.JPG

ISO 3200

http://marcusgho.com/photogallery/galleries/Untitled%20And%20Unsorted/Flash%20tutorial/420%20ISO%203200.JPG

Okay, we have a much more manageable shutter speed and yes the lighting is pretty harsh and ugly. But notice that as I increase the ISO, the foreground exposure remains pretty constant but the background get brighter as i go from ISO 100-400-3200.

Why is this happening.... as i said, flash has a limited range and will only cover a short range, in this case, it is just the teddy bear. ETTL is smart enough to make sure that Teddy bear is exposure correctly and it adjust the correct amount of flash to it. However, that is only the flash affecting the bear.

As i said that the flash cannot reach the background, it is only exposure by the available light. At the same shutter speed 1/125, the amount of light lighting the background is the same for ISO 100, 400, 3200. however as ISO 400 is more sensitive than ISO 100, the background is brighter... make sense?

CONCLUSON:

There is a certain sweetpoint for this kind of shot. ISO 400 or 800 for me. Notice how background is affected by ISO. Using flash gives us much more useable shutter speed. Further more by using manual, we can effectively shoot freely without the camera given us unreasonable shutter speed in Av mode. We also know what kind of output we are getting (how bright the background is)

Picture 5,6,7

These are same setting as pic 2,3,4 but i moved my flash to a bounce position facing up. What happens is that the flash shoots to the ceiling where it is bounce back down to the scene. This is very good as it gives a very nice diffused light. Instead of a small 1inchX2inch flash head, you effectively used the entire ceiling as a diffuser. notice how more natural the lighting is. Also notice that is not much different between ISO 100, 400 and 3200 in terms of overal exposre. What happened is that by buoncing of the ceriling, i managed to flood both background and foreground with enought light. This can work if the room is small and the ceiling is not too high.

Pic 5 ISO 100

http://marcusgho.com/photogallery/galleries/Untitled%20And%20Unsorted/Flash%20tutorial/BOUNCE%20ISO%200100.JPG

Pic 6 ISO 400

http://marcusgho.com/photogallery/galleries/Untitled%20And%20Unsorted/Flash%20tutorial/BOUNCE%20ISO%200200.JPG

Pic 7 ISO 3200

http://marcusgho.com/photogallery/galleries/Untitled%20And%20Unsorted/Flash%20tutorial/BOUNCE%20ISO%203200.JPG

FINALLY Compare the ISO 100 bounce file to the orginal no flash ISO 400 photo. Both look pretty nice to me... which is better? It is subjective but I know i can pull off the ISO 100 bounch shot as te shutter speed is so much more useable. Also, i am using a f4 lens which is much cheaper than a f1.4 lens... My point is that with flash, you can get a decent (if different) shot which is useable and sometimes even nicer.

ISO 100 Bounce Flash 1/125 seconds

http://marcusgho.com/photogallery/galleries/Untitled%20And%20Unsorted/Flash%20tutorial/BOUNCE%20ISO%200100.JPG

ISO 400 No Flash 1/5 seconds

http://marcusgho.com/photogallery/galleries/Untitled%20And%20Unsorted/Flash%20tutorial/No%20flash%20ISO%20400%2C1%3A5%20.JPG

Okay... i hope you guys have a better undertanding of what is going on.... I am not done with this as i have not explained how FEC or flash exposure compensation works. But in a nutshell, it simples tell the flash to over/under exposure. This gives the same effect of ISO on the background... except the effect will only affect the foreground. In order words... if you shoot at the same setting and vary the FEC, you can selectively over/under expose the foreground and the background remains equally exposed.

Apr 01, 2005 at 05:48 AM

Charlie H
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p.1 #2 · FLASH 101

Thanks for this thread. I always seem to struggle getting a good balance between ambient and flash. I guess more practice is in order

Apr 01, 2005 at 08:46 AM

Gearfiend
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p.1 #3 · FLASH 101

Thanks, very helpful.

In theory, I know how all this stuff works and what it does, but its really nice to see it in practice. When I first got my camera, I was confused as to why using the flash sometimes made things darker.

I figured it out.....

Please, by all means, explain away......

Simon

Apr 01, 2005 at 09:06 AM

spirit
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p.1 #4 · FLASH 101

Thank you so much for that post, it helped me a lot. I just did a wedding with the 10D and the 550 EX totally indoors and was getting really lousy results. My shots were very inconsistant. I wouldn't change the settings and I would get up to a 1 stop difference on the same shot. I am not exactly what I need to do, but you gave me some ideas to work with. Have you shot with the 550 at all? Do you have any sugestions on what I might be able to do with that particular flash? I have heard that it is very inconsistant, and I was reading about the new 580 EX and am thinking about it, it talks about how it fixes most of the problems I am having. Any feedback would be appreciated.

Thanks
Mike

Apr 01, 2005 at 09:25 AM

infosecgeek
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p.1 #5 · FLASH 101

Either its me or my camera is stupid... I can never get properly exposed shots with the 550 in bounce or pointed directly at the subject in either P or AV, my rule of thumb for indoor flash is M Mode (550 set to Auto) 1/100-1/125 ISO 200 F/8-F/11 FEC +1/3-2/3

I have tried this with 4 bodies now, and unless I am doing something wrong (P Mode, is doing something wrong possible?)

This always gives me consistent indoor low light (family room type) exposures.

Apr 01, 2005 at 09:25 AM

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p.1 #6 · FLASH 101

Another thing you need to know for flash photography is how you meter.... That will determine how much flash the camera will output. As i said, the flash will only affect the foreground, so you have to make sure you know what you are metering and what to expect.

Fo example, if I wanted to expose my teddy bear correctly, i need to know how my camera is metering. For the Rebel 300D, I cannot chose it but in manual mode, it is always center weighted. So i will use my Flash Exposure Lock button to lock my expoure on something that is close to neutral 18% grey. Upon pressing this button, the camera will fire a fre flash and determine how much flash it needs to fire off. I will then recompose the picture and fire. Next check the LCD and historgram and play around with FEC until you get a setting you like.

The trick is that if you consistantly meter off the same place (for example if you are shooting people, their cheek is a good place), and Flash Exposure Lock, there is no reaason why you will be getting inconsistant results. What I think a lot of people are doing are simply composing the shot and firing the camera. If they were in evaluative, the entire scene might be too dark and the flash output the camera choose will be too much and vice versa. If you are in spot/center weight and the point where the camera was pointing was either a tuxedo (pure black) or a wedding dress (pure white), your camera will be confuse and consistantly give you incorrect exposure....

Remember you need to know how your camera works. It is a very simple machine trying to think like us and it is easy to fool it

Apr 01, 2005 at 11:56 AM

discreet
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p.1 #7 · FLASH 101

I have the 550 too but i decided to use the 420 to show that it has enough juice for most cases. The 5XX flashes (550 and 580) are more powerful and recharge faster while the 580 is supposedly more accurate when you use it with an ETTL 2 body. I get consistnat results with both my 420 and 550 and even with both using an ST E2. The trick is the metering and locking the metering using Flash Exposure Lock.....

Use it it is your friend

spirit wrote:
Thank you so much for that post, it helped me a lot. I just did a wedding with the 10D and the 550 EX totally indoors and was getting really lousy results. My shots were very inconsistant. I wouldn't change the settings and I would get up to a 1 stop difference on the same shot. I am not exactly what I need to do, but you gave me some ideas to work with. Have you shot with the 550 at all? Do you have any sugestions on what I might be able to do with that particular flash? I...Show more →

Apr 01, 2005 at 11:58 AM

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p.1 #8 · FLASH 101

Anyway guys, I recommend you try to recreate the results i am getting. The settings for each photo is listed there and you can try it yourself. Remember to check what you are metering at and past experience tells me the more control you have over it the better. That is why spot metering/centre weighted is the most desired as you can really Flash Exposure Lock on a very small area and miminize the chance of the camera being fooled.

It is a very simple concept and I hope you guys get it

Other Flash tips I will include later:
1) Use of Diffuser, Why bigger is better..
2) Flash Exposure Lock.. a more comprehensive write up
3) Flash Exposure Compensation.... ditto
4) Getting the camera off the hot shoe.. why it is desired
5) Coloring your flash with gels...
6) Dragging the shutter
7) Fill Flash
8) Wireless ETTL system

Apr 01, 2005 at 12:04 PM

nutek
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p.1 #9 · FLASH 101

ETTL is usually tied to the currently selected focussing point. Check where your focus point is, and whether is it covering a predominantly light or predominantly dark area. Adjust your Flash Exposure Compensation (FEC) to compensate accordingly.

Apr 01, 2005 at 02:22 PM

Charlie H
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p.1 #10 · FLASH 101

Can you do the "dragging the shutter" and "fill flash" soon as I have my first wedding on May 27th and I am still a bit unsure on these two

Apr 05, 2005 at 04:42 AM

Tim Wild
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p.1 #11 · FLASH 101

That's a great basic tutorial discreet, i'm sure it'll help many people

On a completely different note, I read a fanatstic concert photography tutorial yesterday, it might interest some people too, though it has no relation to this thread.

http://www.photo.net/learn/concerts/mirarchi/concer_1.htm

Edited by Tim Wild on Apr 06, 2005 at 12:23 AM GMT

Apr 05, 2005 at 05:42 AM

meejahor
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p.1 #12 · FLASH 101

Sorry I haven't read the whole thread but it must be very complicated to be that long.

1. Set the flash to E-TTL with head at 60 degree angle, ideally with diffuser.
2. Set the aperture you want, meter the scene, set the shutter speed two stops under-exposed.
3. Take the picture.

That will get you the shot in most situations.

Apr 05, 2005 at 05:51 AM

GoldenBoy
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p.1 #13 · FLASH 101

Canon does have a tutorial on all of this... Don't recall the link but it's tons of pages.

Here's another link I find useful. http://photonotes.org/articles/eos-flash/

Apr 05, 2005 at 06:16 AM

discreet
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p.1 #14 · FLASH 101

Charlie H wrote:
Can you do the "dragging the shutter" and "fill flash" soon as I have my first wedding on May 27th and I am still a bit unsure on these two

Sorry guys, I have been very busy and do not have much time to get around this little tutorial...

**I will upload the photos in a while**

Anyway let me try to explain "dragging the shutter" and "fill flash"...

1) Dragging the shutter.

The concept behind dragging the shutter is simple... to me, it is simply taking a picture with flash but the shutter speed used is way longer than the recommended 1/focal length

"Why do people do this?" you may ask... the reason is by dragging the shutter, you can gain 2 things:

1) Your background becomes more bright
2) You want to have that little motion blur which gives it a nice glow to it

1) Background Brighter
okay set your camera to MANUAL f4 (or widest) shutter 1/125, ISO 400, flash on.
Take a picture... chance are your background will be pretty dark
Okay now switch it to Av mode f4, ISO 400, flash on
Depending on the scene, the camera might give you a shutter speed of 1/5 seconds or even 1 sec...
By taking the same picture, you will notice that the background is noticable brighter

Why is this happening??
This is similar to pumping up the ISO as i shown in my first post. After the initial burst of light from the flash, the sensor will start to pick up the light from the background. If you are using a fast shutter like 1/125, the sensor is not going to pick up much light and pumping up the ISO will give you a brighter background. SO, if you have a shutter of 1/15 second instead, physically, there is more light coming in and the background will become brighter...

If that is the case why bother pumping up the ISO and increasing noice

The answer is in the second part

2) Motion Blur

Okay another side effect of dragging the shutter is that you will have "motion blur". This effect requires that either you subject starts to move or you move the camera. This is a very interesting effect and it is hard to describe and the best way is to just play around with it

If you are hand holding a 2 second f4 ISO 400 flash on shot, you can possible keep it steady. Since the shutter is so long, there is a chance that the background exposure might catch up with the foreground. The combination of high ISO and long shutter might give you an exposure that is the same intensity as the flash-lit foreground.

So you cannnot handhold that shot... and thus the resulting picture will show a nice glow around the foreground.

There are other creative ways to exploit this. One example is in a ballroom where you have people dancing... by dragging the shutter and panning( to keep up with the dancers).. you will have a surreal effect in that the dancers are caught stop in motion by the flash, but the background and the rest of the dancers are a horizontal blur...

Okay, i will talk about fill flash later...

Apr 05, 2005 at 07:26 AM

meejahor
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p.1 #15 · FLASH 101

discreet wrote:
The concept behind dragging the shutter is simple... to me, it is simply taking a picture with flash but the shutter speed used is way longer than the recommended 1/focal length

This needs clarification.

The 1/focal length rule relates to avoiding camera shake, ie: a 50mm lens needs at least 1/50s exposure and a 200mm lens needs at least 1/200s exposure. The rule has nothing to do with ambient light, ie: if you need 1/200s at 200mm then you'll still need 1/200s at 50mm.

When it comes to dragging the shutter, the shutter speed relates to the amount of ambient light. For example if you want to shoot at f8 and that requires 1/60s then you might under-expose by two stops and shoot at 1/250s. This will give you a nice fast shutter speed, it will allow ambient light to add some natural colour to the picture, and the flash will give a correct exposure for the subject.

Focal length is basically irrelevant in dragging the shutter.

Apr 05, 2005 at 08:24 AM

Gearfiend
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p.1 #16 · FLASH 101

Question...

I understand whats being said, but one thing doesnt make sense.

I get that if I use the flash, it will only light the foreground. I also understand that the benefit of having the shutter open longer will help properly expose the background. The question I have is that if I meter the flash to the foreground, thus properly exposing it, then leave the shutter open longer, will I not overexpose the foreground?

Thanks

Apr 05, 2005 at 09:13 AM

meejahor
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p.1 #17 · FLASH 101

You meter for the background.

At a party, for example, just meter the whole scene because it will either be uniformly lit or the lights will be changing so fast that it had might as well be.

Outside you would probably meter the sky.

Apr 05, 2005 at 09:23 AM

Gearfiend
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p.1 #18 · FLASH 101

Im sorry if Im being stupid.....

If I meter for the background, then use the flash which affects the foreground, will I not overexpose the foreground?

Apr 05, 2005 at 09:34 AM

meejahor
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p.1 #19 · FLASH 101

The short answer is: No.

The long answer is: No, because the background will almost always be brighter than the foreground.

Imagine these two scenarios:

1. A party. You meter the whole frame and under-expose. The subject and background will both be under-exposed. You take the shot, the flash fires the correct amount of light to properly expose the subject. Result: Subject is properly exposed, background is under-exposed.

2. Friend stood on a beach on a bright sunny day. You find a good exposure setting for the scene (sky not too bright, beach not too dark) then under-expose. Same again, you take the shot, the flash fires the correct amount of light to properly expose the subject. Result: Subject is properly exposed, background is under-exposed.

Remember: You MUST under-expose using shutter speed, not aperture.

Apr 05, 2005 at 09:43 AM

discreet
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p.1 #20 · FLASH 101

it depends....

in an ideal case.. the light from the flash will overpower the ambient light for the foreground. I would definetely meter for the foreground (ie the person's face) as this is how TTL Flash works.

If you meter for the background, you will get the correct shutter speed for exposing the background using ONLY ambient light.

So this is what i do... i shoot in manual and i watch the exposure in my camera... i do an inital meter on the background and adjust the shutter to match. Next i will Flash Exposure lock on my foreground and then i fire the camera.

In this way you meter for the background (adjust shutter) and also meter for the foreground using the FEL

Apr 05, 2005 at 09:47 AM

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