Help

I just took a ton of photos and shot all in RAW. I shot them in daylight with my Rebel XT with Sigma 70-300 zoom lens. I shot photos of an eagle that was only 100 feet away. I had it zoomed all the way out to get close as i could. I set the shutter to 1/250 at f11, and used the 580EX flash. The photos look horrible. They are all under exposed. Dont know how they could be underexposed using that supposedly great flash and in daylight. I used CS2 to process the RAW into Tif and then use CS2 to lighten the photos so i can see them and the more i try to make CS2 expose the photo the more these little red speckles show up all over the picture. What is that? I thought the reason i was shooting RAW was so that if i shot photos that somehow were underexposed i could recover the data so that the photo would be exposed the way i shot it. The photos were shot in daylight so i dont know whats going on. Am i supposed to process the RAW prior to making it a tif file? Even so i tried that too and red speckles everywhere when i try to expose it properly. Whats the catch. I only have 1 photo thats ok out of about 70, and that one is still to soft.

Wow, f11 at 100 ft is pretty extreme for any flash. How did you arrive at that shutter speed/aperture combo? Using the "sunny 16" formula it would be about right for a bright sunny day, but if it was a bright sunny day, why use flash? What ISO? Maybe more info is needed... As for the red specks, sounds like you have under/over exposure warnings turned on and these are hot spots showing up when you increase the exposure.

Ok the exif info is as follows:
shutter speed 1/250
Aperature f11
Metering evaluative
Iso 400
Focal Length 300
Flash Off
White Balance Mode: Flash
AF Mode: AI Focus

I thought flash was on. I turned it on. It was sunny but partial overcast but i just got the flash and wanted to try it out and since i was less than 190 ft from the eagle i figured TTL would only improve things if my shutter speed was too fast to let sufficient light in. From looking at the info in the software flash never went off. But i still should be able to see the image. Basically prior to processing the RAW file its so dark i can barely see it. Then when i auto levels it lightens things up and introduces red speckles all over the picture and the only way to get rid of the specles is to darken the image to where its barely visible again. What are these hotspots you mentioned? Is that a problem with the camera? Or is it something i can turn off? If i can turn that off please tell me how.
Whats sunny 16 rule? What makes f11 at 100 ft extreme for a flash?
The way i came up with my settings were I went into manual mode. I chose f11 because ive read thru forums that f11 is a good aperature for sharpness thruout and i did not want a shallow depth of field with this photo. I chose 1/250 shutter speed because i was zoomed to 300mm and although it should have been faster, I felt that i could hold it steady enough with that speed to get a good shot without having to go all the way to 1/400 and risk underexposure which happened anyway. The flash was supposed to compensate if there wasnt enough light for my fast shutter speed. But seems it never flashed. I wondered why the pictures kept looking so dark on the lcd screen, but i just figured that RAW could bring out the true colors when i got home. Doesnt seem to be the case unless im doing something wrong. I dont know why flash didnt work. Its working now. Ive only had it for a week. It did work on a smaller bird in a tree, from only about 20 feet away but still didnt do much to brighten the bird up. Im a little disappointed in everything all around. Camera, flash, CS2. I spent so much money on this trip to take some photos and ended up with all junk not even worthy of showing anything i shot. I thought the flash was supposed to zoom when the camera zooms. I dont see the flash zoom at all unless i go to manual and zoom it myself. Maybe thats the way its supposed to be but the book doesnt say. I need help badly. And Ive read all the forums. Thats why i took the trip i figured i knew enough to at least make one good photo. Wish there was a way to show you my pics but they are all junk tif files that are 45 megs each. Dont want to delete them and find out later they could have been fixed.

First you have to under Guide Number. Do a search on this topic. There are plenty of good threads on this topic. In a nutshell asking the flash to properly illuminate a subject at that distance is a stretch. In order for that to work you would need a snoot to focus the beam to the subject. Off hand I don't know what the actual distance is. The rule of thumb for shutter speed is 1 over the focal length. The sunny 16 rule has been discuss over and over again. In brief, Sunny 16 means on a sunny day set aperature to f16 and shutter speed to 1 over the iso.

As for post processing in RAW, RAW can provide room for adjusting exposure after the fact. But this done before you convert it to TIFF, JPEG, etc. It also allows you to adust the white alance at that time as well. Although you can make level/curve adjustment in PSCS it is very limited before it color shift beyond recovery. You can also use brightness and contrst too but even less affective.

Just a thought - isn't the max shutter speed for flash 1/200sec on the XT? That would explain why it didn't fire...

Oh, the distance for the canon 580EX is 150 feet and i was at about 100 ft away. I shot at a shutter speed that was less that whats recommended for a zoom of 300mm, but that should have only introduced blur not underexposure. I set it for a slower speed than what recommended to help prevent underexposure willing to sacrifice some sharpness. My problem here is why did i get underexposed and what are those red dots everywhere. Should a slightly overcast day cause underexposure when shooting something 100 feet away at the proper shutter speeds for zoom range and an aperature of f11. Question 2 is can these photos be fixed, and Question 3 what did i do wrong to get the underexposed photos? Oh and how do it turn off the red dots underexposure warning?

No with the 580EX flash will sync with the camera all the way up to 1/4000sec. I just tried it. I even set flash at like 1/64th power and shot at 1/4000sec and shot continuously at 3 frames per second and the flash went off 3 times a second just like the shutter.

According to the specs provided by Canon
Flash Range


(At ISO 100, with 50mm f/1.4 lens at f/1.4) -- Approx. 1.6 to 98 feet / 0.5 to 30m

The range of the less decease as the fstop increases (smaller aperature) as you can see from the above example at f1.4 and iso 100 the flash has a max range of 98ft

As a rough guide for the working distance for a flash use this formula

f/ no = guide no. / distance

Now the 580ex has a GN of 58m at ISO100

If you double the ISO you multiple the GN by a factor of 1.4, in your situation you were shooting at ISO400 so the GN would have been 113m or 375 feet so...

f/ no. = 375 / 100 = 3.75

Even if the flash had fired it would have made little difference as it would have been more than 2 stops under.

I'm not sure what you mean by red dots - what software are you using to process the raw file?

Q2: It would help if you posted a jpg.

Q3: It seems like you based your settings on the focal length and desired DoF rather than the light that was available.

So what does that formula mean to me. The final 3.75 means what? I am totally lost. I know youre not saying that the subject would need to be 3.75 feet away for the flash to reach it or are you? Or are you saying i would have needed an f3.75 to make the flash reach which would have been impossible with that lens. On to the red dots. The first response to my post a person said that the red speckles all over the photos might be some over/under exposure warning that i might have enabled. He called the speckles hotspots. The raw file is too dark you cant even see the wings so i use CS2 to process it. I up the exposure so that i can see the wings and red spots appear everywhere as you can see.

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Yes, the formula gives the f/ number needed for the distance and f/3.75 is what you would have needed at that distance and ISO for the flash to light the shot.

The red spots aren't a warning as the other poster suspected, just severe noise from trying to correct the exposure. Some raw conversion tools have an option to highlight under/over exposed pixels but that's not the case here I'm afraid.

The flash may have fired, but did NOT provide full power. For ordinary use, you must use the flash with shutter speeds no faster than 1/200 second. Otherwise, you are using the "high speed sync", and that can't be done with the flash providing its full power.

Reading through your posts in this thread, it is fairly obvious that you need to learn about exposure control and metering. You used two "rules of thumb" - one to choose an aperture that makes the lens look good, and another to stop action at a long focal length. You apparently didn't use any meter, built-in or handheld, to determine how much light was available and what settings would provide a decent exposure of the subject even without the flash. You really need to learn about the basics of ISO settings, shutter speeds, and apertures, and how they all relate to allow the camera to make a suitable image of a subject. Using a meter is a critically important step in determining the settings.

You should consider the flash that you have useful for out to maybe 25 or 30 feet maximum. Yes, you can stretch that, but it will require really knowing about a lot of things to get that to happen.

Unfortunately I am running out of time now, but there are many links to very helpful web sites with all the information in the "sticky" posts in these forums. I hope to check in later and if others haven't pointed you to some, I will.

Youre right about metering i dont even know what that is. The book that came with the XT only mentions the different metering modes but i have no idea what they do. I guess if i did my photos might not have suffered so much or at least i wouldnt have been so let down by my photos. I only chose the 580EX over the Sigma Super because i thought it would go out to like 150 feet. Didnt know all that other stuff, again the book doesnt explain in detail this stuff like that formula that was posted a few posts up. Thanks for that formula. One question about the zoom flash. When its in ETTL why doesnt it zoom when i zoom the lens? The flash lcd screen shows my new zoom length but i never see the flash actually zoom. I always thought it was supposed to but maybe not. I did however go to manual on the flash and i can manually zoom the flash and it does move. What gives? Looking forward to hearing more of you helpful information. I will be checking back here occasionally to see what i can learn. Thanks.

There are limitation to the zoom capability in the 580. You can't expect the flash to zoom to match the focal length of your particular lens. Most flashes w/ auto zoom max out some where around 100mm.

The other thing you have observe is that the flash will fire even at 1/4000. When they are talking about syncing they mean syncing the flash to the physical shutter curtain. The sequence of events is as follow, the shutter release is depressed and the flash prefires and light exits the flash illuminates the subject and turn returns to the camera where it tells the ttl sensor the proper duration the flash must be on and then the main flash fires making the same trip back to the camera where the shutter is wide open to expose the film/sensor. All this takes time even if it is just fraction of a second.