sleahy73 Posted April 16, 2008 Share Posted April 16, 2008 Hi all, I've been lurking about, still. I really enjoy reading all of your posts. Last week I had an opportunity to take some pictures of an informal concert type performance. It was a neat experience, but it has left me with a lot of questions. I was using my K10D in manual mode with a Tokina AT-X Pro 28-80mm f/2.8 and a AF-540 FGZ flash in P-TTL mode. 1. Why would there be (roughly) a 1/3 stop variance between more or less exactly the same picture (see photos 1 & 2)? 2. Why did changing the ISO have little, if any, effect on the exposure (see 4 & 5)? 3. Why would consistent, even, admittedly low light, even with use of the flash, yeild such uneven and inconsistent results?<div></div> Link to comment Share on other sites More sharing options...
sleahy73 Posted April 16, 2008 Author Share Posted April 16, 2008 2 f2.8 1/40th ISO 200<div></div> Link to comment Share on other sites More sharing options...
sleahy73 Posted April 16, 2008 Author Share Posted April 16, 2008 3 f2.8 1/40th ISO 200<div></div> Link to comment Share on other sites More sharing options...
sleahy73 Posted April 16, 2008 Author Share Posted April 16, 2008 4 f2.8 1/40th ISO 400<div></div> Link to comment Share on other sites More sharing options...
sleahy73 Posted April 16, 2008 Author Share Posted April 16, 2008 5 f2.8 1/40th ISO 800<div></div> Link to comment Share on other sites More sharing options...
sleahy73 Posted April 16, 2008 Author Share Posted April 16, 2008 There doesn't seem to be anything in any of the pictures to fool the flash into underexposing the scene. In #5 I think I had the flash +1 EV (though I can't find the EXIF data to prove it), and I had to do that every time I was over on that side in order to get anything close to a proper exposure. These are 5 of 7 shots taken within the space of a few minutes and are in sequential order. I took about 130 picture that night and these are anomg the earlier shots. I was using fresh batteries. What am I missing here? Link to comment Share on other sites More sharing options...
sleahy73 Posted April 16, 2008 Author Share Posted April 16, 2008 An error... #5 was at 1/8th sec. Sorry. Link to comment Share on other sites More sharing options...
mc2imaging Posted April 16, 2008 Share Posted April 16, 2008 You might be surprised what little things can reflect back a bit more light and make a big difference on the exposure. The trick is that the metering is done off the pre-flash, so if something that was moving happened to flare while the pre-flash was firing, but it moved enough not to flare during the actual exposure, you'd never know why they were metered different. Changing the exposure parameters won't change the final exposure until you hit one of two limits: 1. You cranked the shutter speed down slow enough that you have more ambient light exposure than flash exposure. 2. You cranked the ISO down or closed the aperture down far enough that the flash can no longer compensate for your adjustments (i.e. it is firing at full power and still can't produce enough light. In P-TTL mode, adjusting the aperture or ISO just means that the camera will adjust the power output to match your change to produce the same EV. If you cranked up your ISO one stop, the flash merely produced one stop less light, giving you the same exposure value. If you want to under or over expose what the camera is metering, you need to add or subtract an EV compensation on the flash. Link to comment Share on other sites More sharing options...
mc2imaging Posted April 16, 2008 Share Posted April 16, 2008 <i>...There doesn't seem to be anything in any of the pictures to fool the flash into underexposing...</i><p> I'd say the chrome on the trap set is exposed perfectly in all... Link to comment Share on other sites More sharing options...
mc2imaging Posted April 16, 2008 Share Posted April 16, 2008 OK, I KNOW I'm gonna catch it for that last one so I'll explain it, then let people beat me up... I bet if you look at the histogram for those last few, you would see a spike at the right end. As far as the camera was concerned, you were blowing it out. When you are in a situation like this, you need to find alternate plan like bouncing, defusing, or shooting with the flash in 'A' or 'M'... Link to comment Share on other sites More sharing options...
deaner66 Posted April 16, 2008 Share Posted April 16, 2008 Not to sound flippant, because I don't mean it that way, but if you shot over 130 shots, why not just go manual? After a little practice, you get a good feel of where to start, and from there, just chimp until things start shaping up the way you want them. And by manual, I'm referring to your flash. Personally, I would try to figure out a way to get your flash off the top of the camera. But barring that, get a Omni-Bounce cover for your flash to deaden the light a bit. Link to comment Share on other sites More sharing options...
jgredline Posted April 17, 2008 Share Posted April 17, 2008 All good advice. I agree with Steve and learn to use your flash in manual mode....I have the Pentax 360 flash unit and find it extremely powerful...as powerful as it is, it is useless in auto mode at least for me....The first image in this series of three is basically letting the camera figure things out...As you can see it could not...Context.. Here I am appx 40 feet away from the band in conditions so dark that the K10D could not focus...I found a shiny spot, locked focus and fired...I was using the K10D with Tamron 28-75 F/2.8 The good images are set with the flash in full manual mode and pretty much maxed out, yet I still had room for more using the cameras EV and ISO settings... Link to comment Share on other sites More sharing options...
jgredline Posted April 17, 2008 Share Posted April 17, 2008 <a target='_blank' title='ImageShack - Image And Video Hosting' href='http://imageshack.us/'><img src='http://img254.imageshack.us/img254/6587/tron2rn0.jpg' border='0'/></a> <a target='_blank' title='ImageShack - Image And Video Hosting' href='http://imageshack.us/'><img src='http://img402.imageshack.us/img402/3756/tronuw4.jpg' border='0'/></a> <a target='_blank' title='ImageShack - Image And Video Hosting' href='http://imageshack.us/'><img src='http://img247.imageshack.us/img247/5522/tron1dw4.jpg' border='0'/></a> Link to comment Share on other sites More sharing options...
sleahy73 Posted April 17, 2008 Author Share Posted April 17, 2008 OK, thanks for the responces and suggestions. I had the camera in Manual mode because I knew the scene would fool the camera's sensor. I guess the flash is just as dumb. That was really only the second time I had put a flash to serious use. I thought the chrome was such a small percentage of the frame that it wouldn't factor so much - guess I was worng. Yeah, it would be cool to get the flash off the camera, but I don't have a bracket and I was shooting this more photojournalism/event style... meaning, I was just doing it in the fly and I really don't know what I'm doing. (No offense to anybody else, just refering to myself here.) I must admit, I'm pretty intimidated by all of those guide numbers and estimated distances, etc. Admittedly I haven't taken a great deal of time with it yet - when I do, I'm sure I'll figure it out, but the couple of times I've read about how to use manual flash I've just gotten confused. Anyway, thanks for your help. Sean Link to comment Share on other sites More sharing options...
mcmanamey Posted April 17, 2008 Share Posted April 17, 2008 Sean - you would NOT believe what ONE little mirror chip on a disco ball will do at a wedding! And being on a bracket, and bouncing off the ceiling actually make that particular situation worse!! Link to comment Share on other sites More sharing options...
michael_kuhne Posted April 17, 2008 Share Posted April 17, 2008 Sean, Maria is right about any strong refection of light affecting the meter. Also true of glass or mirror in the backgroud, or large, white background surfaces. I have shot only a few flash shots with digital. But many with my Pentax film models. I have often shot using full program, as well as manual mode and TV and AV modes. Always with TTL or P-TTL. Any problems I have had with inconsistent results have been due to the above reflective conditions, or from the flash unit being temporarily underpowered. In very dark suroundings where the flash must supply most of the exposure, full charge recycle time is longer. Also, though the auto flash zoom is sometimes convenient, it eats up juice. Manually set the flash FL to the widest you will be shooting at, and see that it stays there. No flash zoom. Use fresh charged batteries, and under dark conditions, wait a bit longer after the ready lamp comes back on. Make sure your flash comp control on body and on flash is set at 00. Link to comment Share on other sites More sharing options...
michael_kuhne Posted April 17, 2008 Share Posted April 17, 2008 Btw I wish Pentax would bring back the excellent on board dual-flash system of the Pz-1p, and aslo the option of TTL or P-TTL. I think I may start another thread on this matter and throw in a couple of examples. Link to comment Share on other sites More sharing options...
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