Underexposed frog flash Photography

I recently tested my hand at using a flash as my only illumination

source. I spent an evening shooting a frog chorus at night, and found

my images were underexposed by about a full stop. The set up I used

was as follows: Canon A2 body, 300 f/4 lens with 25 mm extension tube,

off camera 550 EX, Provia 100F. I shot on manual TTL at F 9.5 and

1/90th or 1/125th. Frogs were approximately 6 ft. from the camera.

The frogs and background were pretty close to middle tone. The frog

and the leaf it was sitting on took up about half the frame with the

remaining portion of the background some distance away. I realize

that TTL is not infallable but I was hoping someone could help explain

why I got such underexposed shots. I guess what really perplexed me

is that the 550 EX gave me a proper exposure indication. I know that

if the subject does not fill a large portion of the frame then

exposure problems can occur but I would have expected an over-exposure

with the black background. Of course I can go out and dial in a + 1

compensation but I was just wondering if there is something I missed?

You seem to be doing everything right. Was there a bright reflection from the flash?

Seems like you covered most of the things that could have gone wrong. There is no way you had the exposure compensation set on the camera, is there? Except for the bright reflection that the previous poster mentioned, I can't think of any other reason except a glitch in your equipment. I'd try and do a test shooting a non reflective subject under similar circumstances, and see if it does it again.

Thanks for the response, I think I may have found a possible explanation. It had finished raining about 20 minutes prior to the shoot so the leaves and everything were very wet. I guess its possible that the leaves were reflective enough to cause the underexposure. I didn't think of it before. Most of the time, the frogs only call after a heavy rain, so wet is usually the prevailing condition. I'll just have to shoot again with a + 1 exposure dialed in and then run a test on a dry night (possibly leaves only) and see how they compare. Thanks!

Ryan,

Sorry to hear about the disappointing results - hope you get another chance soon. I don't know if this is at all relevant since it deals with Nikon equipment, but my experience with macro shots (loosely defined - anywhere from 1:5 or so to 1:1)with TTL metering is that my rig (and this happens with 2 different Nikon N70 bodies) routinely underexposes these shots. I would think that the most likely exposure error when shooting frogs at night against a water background would be for TTL to overexpose the frog, especially if there's a significant amount of open water in the frame. My experience is that animals sitting at the surface of the water typically have a higher reflectance than the surrounding water surface, especially if you're shooting anywhere close to eye level of the animal, and the meter can be fooled by all the low-reflectance water surface around the subject and thus cause overflashing (unless there are irregular wet surfaces that cause bright reflections and shut off the flash prematurely). So it's especially confusing when underexposure results. None the less, when doing macro stuff with my Nikon bodies, a 200mm macro lens, and SB-28 flash, I routinely dial in +0.7 or +1.0 overexposure on the flash, depending on the color of the subject, and generally it gives me perfect exposure. Incidentally, I've read on one of these forums that at least some other Nikon users have found the same problem, though it's never been adequately explained for me. How about posting one of the underexposed shots on the critique forum and let some of the whizzes there have a go at the problem?

I use EOS gear (1V and 1n), and my first question is whether you checked the "flash coupling distance" scale on the flash prior to taking the photos.

 

If you were shooting in the dark of night, f9.5 (and 1/90-1/125 sec.) is likely way too "fast" for this flash to be able to keep up at a distance of six feet (in effect, the inverse square law of light). Suppose you repeated the same conditions, and that initially you metered ONLY THE AMBIENT LIGHT without regard to flash, but after selecting f9.5 and, say, 1/90 sec. in M mode, you then checked the A2's exposure level indicator (you know, the "<-//->" looking icon) in the viewfinder. No doubt, you would find that it indicated under-exposure (<--), but this indicator does not tell you how MANY stops under-exposed the f9.5 and 1/90 sec. values are. To figure this out, you would have to begin "opening up" the exposure until the exposure indicator showed "<-//-> rather than "<--". (Or, you could switch to P mode and simply look at the values the camera would then choose, and compare those to your manually selected values to get some idea of just how many stops under-exposed the latter would be). My guess is that if you did this, you would find that your chosen values in M mode would be many stops below what the camera would pick. This difference is important, and if you then turned on the properly connected flash, the displayed flash coupling distance should reflect just how inappropriately small f9.5 was, and the flash coupling distance should begin to expand as you progressively opened up the aperture. (As I recall, the aperture is the most critical value governing the coupling distance).

 

My suggestion would be to repeat the shoot as best you can, only this time mount the flash on the hotshoe, choose *P mode*, and initially, set no flash exposure compensation whatsoever--let the camera and flash do their thing (and pay attention to any blinking icons in the viewfinder, etc.). Shoot slide film, and see what you get. If the results are more to your liking, then (after carefully re-reading the owner's manuals for the flash and camera), try shooting this situation in Av mode (using a tripod, of course), paying close attention to the flash coupling distance indicator, as you gingerly try to decrease the aperture a bit, using the P mode values as a starting point. Also, consider at some point repeating this shoot while pushing the Provia 100F to 200 ISO (for a 1 stop push) or even 320 ISO for a 2 stop push.

 

Finally, it is of course possible that you did not have the off-camera shoe cord conections seated properly (this is surprisingly easy to have happen), or that something is indeed malfunctioning, but I've been using EOS gear since '94 and have been fortunate to so far not experience any breakdowns. To date, all of my EOS gear "problems" were soon traced back to user error.

Kurt: Thanks for the input. I did check to make sure that the flash was seated properly on the off shoe cord as I have shot on several prior occasions when it was not seated properly. In addition, I did check the flash distance range on the 550 and it gave me a range of almost 4 meters which was well within the range of my subject.

 

 

I normally shoot in AV mode. However, because in this situation there was absolutely no ambient light (as far as the camera was concerned) I chose manual and selected f/9.5 and 1/90th as my best compromise to gain sufficent depth of field and minimize camera vibration. I think you're right about the aperture being more important though and I'll probably try shooting at f/8 and maybe f/6.7 next time.

 

Also, next time I'm going to just bracket my flash compensation. I'm really beginning to think that the wet leaves were reflective enough to cause the underexposure.

Oh yeah, Peter, posting one of the images is a good idea but I don't have a scanner at the moment :(.

Ryan: Do try shooting this situation in P mode, along with your f6.7 efforts. I think you'll be surprised.

I'll give it a try Kurt, thanks. Now I'm just waiting for it to rain again!

Ryan: It might also be interesting to try a few follow-up shots with the flash set to manual mode, gradually decreasing the power downward from "full". If the reflectiveness of the wet leaves is in fact the culprit, then reverting to manual flash mode should remove the TTL factor and the putative 'inappropriate' quenching of the flash as a consequence of this reflectivity. It would also be interesting if you could try an EOS 1V or EOS 3, in which the Flash Exposure Lock (FEL) feature could be employed together with spot metering.

 

The question of why the flash's exposure compensation indicator would erroniously indicate correct exposure continues to nag me, and I plan to review my Canon literature in the near future to try and understand this. I'll let you know if I find anything.

Sorry for my error: I should have said "flash exposure CONFIRMATION indicator".

Hi Kurt: indeed, another good idea. I'll try all of them as soon as we get another rain. Right now it is hot and dry. I like the idea of trying an EOS 1v, send me yours to test and I'll let you know how it turns out : ).

I'll get it in the mail right away...

I somehow remember that extension tubes cost light. Maybe that has something to do with it. But then you said you used TTL flash or was it manual flash?

 

I agree with Kurt. Try plain P mode. Maybe the modern are smarter than us after all...

Ryan; Sorry to fog the issue but I have had the same experience as the Nikon user (always having to add 2/3 to 1 f stop during close up flash photography) with my Canon gear. I use a Canon EOS-3, 100 mm macro lens and a 550EX flash. Most, if not all, of my macro work was too dark by at least 2/3 stop. I called Canon and they told me to send the flash in and see if the "proper messasge" was being either sent to or received from the camera. I read a Morris article stating that the older EOS-3 have a problem underexposing. Well, I haven't solved my problem so I am adding light to most of what I do. Frustating.