Canon 300 f/4, Pop-up flash and Loons

[ross_geredien1]

This past weekend I was shooting Common Loons, and the light was a

terrible flat grey. So I decided to use some fill flash. Only

trouble is, I only have a pop-up. I'm using Canon A-2 body, 300 mm

f/4 IS lens with 1.4x and 2x TC. Has anyone ever used this combo?

Can I expect the flash to be totally blocked by the lens? Or will

some light make it to the subject? I've had success with the 80-

200mm 2.8 with the pop-up, and since they are about the same

diameter, I decided to give it a try.

 

 

Ross Geredien

[kurt_heintzelman]

Ross: Have the film developed so you can judge the results yourself. Slide film will give you the most unambiguous results, but its a safe bet that you need a good quality hot-shoe flash. An EOS 540EZ (or 550 EX if you anticipate upgrading to a more contemporary EOS camera) are good matches with an A2. Also consider buying a "Better Beamer" (or similar) flash extender for use with longer lenses. (IMO, avoid the Lepp Projecta-Flash flash extender).

[mark_lagrange]

Ross, day time fill flash on a ragular basis, not just when the light is poor, is a great idea. If I recall correctly, Art Morris uses it with much of his work. It sounds like you are pretty focused on obtaining great results....and it sounds like you have made something of an investment in your lenses. Don't get cheap with your flash. Invest in a flash powerful enough to make a difference. In addition, you may wish to spend the extra $35.00 on a "projecto-flash" or "better beamer". Using a fresnel lens, this flash extender will focus the beam of your flash tighter and therefore throw the light further. If most results oriented bird photographers (sounds like you are) need this extra flash focusing power in addition to a "real" flash, I doubt that the camera's own pop up will have a chance to contribute to your results (if it even clears the wide end of an f/2.8 lens hood).

 

There are several other technical advantages that the Canon flashes will offer...but I hope this is enough convincing. What other experience does anyone have in using fill flash for bird photography?

 

Hope this helps.

[phil]

Easy way to tell: put the camera on a tripod, pop up the flash, go walk to the distance the loon was away, line yourself up looking down the lens axis towards the camera. If you can see the flash, the flash could see the loon. Anyway, the pop-up on the A2 is so anemic that if you were using an effective 600/8 or 400/5.6 combo at normal

loon-shooting distances, then you are out of luck.

[sam_mahmoud]

Even if the lens doesn't block the flash, the raw distance

to the subject is really pretty far for that little flash

unit. Pop-up flashes are not very powerful. Let's try a

little math.

 

According to the B&H site, the guide number for the A2's

pop-up flash (ISO 100, in feet) is 43-56. If that's

true, then with your lens wide open at f/4 your flash

will "fully" illuminate a subject fully at 10.75-14 feet

with ISO 100 film. (guide number divided by f-stop equals

distance).

 

The good news is that you don't need full flash.

Fill-flash is usually in the range of -1 to -2 stops

less than full flash, depending on whether you like a

stronger or a more subtle fill-flash effect. That

extends your range to about 15-20 feet for -1 stop

and 21.5-28 feet for -2 stops.

 

Using Velvia? You just lost a stop because the guide

number is quoted at ISO100 and Velvia is ISO 50 (arguments

about ISO 40 deferred to another thread), so your

distance is now roughly 11-14 feet for fill flash at

1 stop below full power and 15-20 feet for fill flash

at 2 stops below full power.

 

This sounds to me like it could work, if only barely,

for some applications. You'll have to find the best

combination of: 1) fast film, 2) tame loons, and

3) acceptance of subtle, rather than strong, fill flash.

Shoot wide open, and leave off the teleconverters.

 

And of course none of this matters if the flash is

blocked by the lens.

[patrick_chase]

A correction to Sam Mahmoud's post: Film ISO speed is absolutely irrelevant when determining daytime fill flash range. All that matters is the flash GN and the camera's maximum sync speed.

 

In the case the A2 + EF300, the built-in flash would yield a rated GN at ISO 100 of 56 feet (because it would be zoomed to its longest setting) and the camera's max sync speed would be 1/200 sec. Assuming for the moment that you use ISO 100 film and that you're shooting in broad daylight, the resulting exposure would be 1/200 at f/11. The resulting flash range for full exposure would be ~5 feet (i.e. less than the minimum focussing distance of the lens, if it's a 300/4L non-IS). If you can accept a 2-stop exposure reduction for fill, then the range doubles to ~10 feet, which probably still isn't all that useful except maybe in an aviary.

 

To see why film speed is irrelevant, consider Velvia at ISO 50. Velvia reduces the GN of the flash to 40 feet (56*sqrt(100/50)). It also changes the sunny f/16 exposure at 1/200 sec (the camera's maximum sync speed) from f/11 to f/8. Dividing GN by aperture we obtain a range of 40/8 = 5 feet for a full exposure, which is exactly the same as we obtained for ISO 100 film.

 

To illustrate the principal even more clearly, consider what happens when you drop a 2-stop ND in front of the aforementioned lens (let's also assume that the film is still Velvia). The effective GN of the flash with ISO 50 film and 2 stops of ND is 20 feet, but the sunny-16 exposure at 1/200 is now f/4. The range for full exposure is therefore still unchanged at 20/4 = 5 feet. The fact that a lot of ND _must_ be used to achieve wide-open aperture in daylight with fill-flash (unless you're willing to pay the range penalty associated with high-speed modes like Canon's "FP sync") is why fill flash connoiseurs tend to lug such filters around in the first place.

 

An incidental point of this message is that dinky little built-in flashes are pretty much useless for fill-in, even if/when their light isn't blocked by the lens. My advice would be to strongly consider a used 430EZ or 540EZ, and a Better Beamer or similar fresnel device as well. Adding a 540EZ to your A2 gives you about 90% of the usable fill-flash range of Canon's top-of-the-line body/flash combo (EOS-1v with its 1/250 flash sync, plus 550EX) at vastly lower cost.

 

Regards,

 

Patrick

[sam_mahmoud]

Thanks for the correction, Patrick.

 

I had forgotten that you can get limited by the max

flash sync speed. Obviously the pop-up flash won't

get far using really small apertures, yet the

combination of a relatively-slow shutter speed

and a bright day means the ambient exposure will

force you to use really small apertures.

 

My version of the calculations still makes sense

in lower light -- anywhere where you have the lens

wide open at slower than 1/200 seconds.

 

So Patrick, if you were using a big modern

Canon flash, what would be your strategy here?

Use the flash's full power at 1/200? Or open

up the lens, set a higher shutter speed, and

use the flash in hi-speed sync mode?

[patrick_chase]

Hi Sam;

 

If you're trying for maximum fill-flash range, you'll always fare best by staying at the camera's maximum sync speed.

 

Going to higher shutter speeds and using Nikon's HS mode or Canon's FP mode will reduce usable range by 20-30% (i.e. as you move to higher shutter speeds, the GN decreases faster than the aperture).

 

-- Patrick

[patrick_chase]

In a previous post I wrote:

 

> Using Nikon's HS mode or Canon's FP mode will reduce usable range by 20-30%

 

What I posted was my somewhat hazy recollection. Just for kicks, I decided to test this more thoroughly today. I used an EOS 3 and 550EX, and used the body's flash exposure confirmation display to find the smallest aperture which still yielded a full exposure with a fixed subject (my living room wall) at various shutter speeds, with and without FP sync. Here are two data which tell the story:

 

At 1/200 (w/o FP mode), the smallest usable aperture was f/22

 

At 1/250 (w/ FP mode), the smallest usable aperture was f/10

 

For fill-in, going from 1/200 to 1/250 would enable you to open the aperture by 1/3 stop while maintaining correct ambient exposure. Because f/10 is 2-1/3 stops wider than f/22, the data above imply a 50% range loss (i.e. 2 full stops) from using FP sync, rather than the 20-30% I previously stated.

 

Sorry 'bout that!

 

-- Patrick

[mikemilton]

OK, Was the point of the original question to actually achieve any meaningful fill or just to provide a catchlight in the eyes and what is the implication of this difference?

 

So, if al you want is a glint from a highly reflective target, how important are guide numbers?

 

Any experience?