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ITTL vs TTL
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I dont know whether tis is a stupid question to ask but eversince i bought my D50 i still havent figure out whats the difference btwn the ITTL and TTL metering thing. I couldnt find anything to explain it in the guide. Someone help me out....
Thankz
Posted at 10:51PM, 10 June 2006 PDT
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i-TTL is a flash mode that enables automatic balanced fill-flash. What it does is that the camera automatically controls the flash output to keep both the subject and background properly exposed. THe popup flash in your D50 has this function.
For TTL flash mode, only the main subject is correctly exposed regards of the background brightness.
However, TTL is also the acronym for Through The Lens. TTL metering means that the camera measures the light coming into the camera lens to caluclate the exposure.
Hope this answers your query.
Posted 73 months ago.
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one of the reasons ITTL works so well at fill in flash is it is designed to work with the Matrix metering in your camera.
Mike[radiorabbi]
Posted 73 months ago.
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i-TTL works by firing a pre-flash before the mirror is raised when you take a picture. The meter evaluates this preflash, as well as other information (Aperture, ISO, selected AF point, AF distance, Flash exposure compensation) and determines an exposure. All TTL flash with the D50 is i-TTL. the flash then fires at the selected power level after the mirror is raised and the shutter open
TTL flash however reads the exposure via reflected light off the film to a flash sensor in the mirror box (or the camera meter in the case of the F3). It is more accurate than a pure pre-flash based system, especially in it's late incarnations (which use a pre-flash for initial calculations as well as the flash sensor reading off the film, aperture, selected focus point and and focus distance). But due to the high-reflectivity of Digital sensors, it doesn't work well for digital, and only 3 DSLR's have used it at all successfully (Fuji S2 Pro and Pentax *ist D and *istDS)
Now you might be thinking of the difference between TTL and TTL-BL (or i-TTL Balanced Fill Flash). TTL in this aspect meters only for the flash exposure, ignoring the ambient exposure, this is the mode to use when shooting with the flash as the main light. TTL-BL balances the ambient and flash exposures so as to use the flash to fill in shadows and bring out the subject. It works fairly well but seems biased to use the flash as the main light. I prefer to use TTL-BL with the Flash Exposure Compensation dialed down a stop or so (-1). The on-board flash on the D50 does TTL-BL only, the mode is selectable with the SB-800 or SB-600.
Posted 73 months ago.
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@Mawz: Thanks for the informative post. I had no idea of how sophisticated the flash metering is. Cool.
Posted 73 months ago.
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Josh: It's very sophisticated, I'm actually just brushing the surface.
i-TTL is pretty amazing, especially once you start playing with the wireless capabilities. the only issue with it is Nikon's insistance that Balanced Fill Flash should bias towards flash exposure instead of ambient. At least i-TTL only needs 1 stop of correction, the older Matrix Balanced Fill Flash and 3D Matrix Balanced Fill Flash systems need about -1.7 stops to get a nice balance between flash and ambient.
Posted 73 months ago.
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Thanks for the insight guys......
Posted 73 months ago.
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@Mawz, Thanks! Finally a thorough (albeit a bit technical) explanation of something that has both delighted and mystified me about the D50. I knew there was some pretty sophisticated stuff going on inside the camera. How else could the D50 "automatically" calculate the proper exposure using the built-in flash for one shot with the subject about 2 ft. away, and then also properly expose a subject that 's about 15 ft. away in the next shot. What matters is that it works. Thanks.
Posted 73 months ago.
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Mawz. Read your comments above on Balanced Fill Flash and wanted to make sure I understood. I'm a new D50 owner and was recently shooting some outdoor snapshots in bright mid-day sun. Popped up the onboard flash to fill in the shadows like I used to do with my N70 and got horribly overexposed, washed out images (shooting aperture priority with fill flash selected). I called Nikon technical support to ask for advise and the guy said to set the flash mode to slow sync. Slower shutter speed for overexposure? Riiiight!
From the above, I think I understand that it's a common problem defined by the camera's programming. The cure would be a -1stop correction. I dunno though, it seems like it needed more than 1 stop to fix...
Posted 72 months ago.
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If shooting in Aperture priority I would get a flash exposure chart (found in flash manual). With flash smaller apertures are used to get correct exposure at closer distances while larger apertures are for longer distances.
If you don't want to use a chart shoot in P and your camera will do it for you. i've found S to be easy to use in controlling flash effects in slow sync.
Posted 72 months ago.
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I just posted one of the sample pics in the pool. Wanted to minimize depth of field but I guess you can't have everything! Thanks for the advise minority report, I'll give P mode a try.
Posted 72 months ago.
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The quick solution would be to shine a Westcott reflector on her and meter off that. But we're talking about flash and I noticed your aperture was 4.5 so I'm thinking the 18-55mm kit lens near the long end, maybe 70mm equivalent.
Now going to my flash chart and guessing ISO 200 (because PS ate some EXIF), for 70mm the flash at f4 covers 1 to 12m, f5.6/0.8 to 8.4m, f8/0.6 to 6m, f11/0.6 to 4.2m, f16/0.6 to 3m, f22/0.6 to 2m. Of these I think f11 or f16 would probably work best and you may want to trim the output further by decreasing your shutter speed because your subject is light and holding a large white object.
Heck in this instance manual is probably the best way to go unless you spotmeter her. ;)
Originally posted 72 months ago.
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minorityreport edited this topic 72 months ago.
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Raul,
All the fill flash images that day were overexposed, but I guess you're right that the one I posted would have been challenging in any case. When I go out next, I'll either narrow the aperture for fill flash or use P mode. I was a little concerned that my camera might have a problem. Funny, fill flash never seemed to be an issue with my old N70, but that's progress for you!
BTW, I saw you dissed the D50 kit lens in your profile. Here's some good news - I sprung for the 18-70mm (D70 kit) lens!
Thanks again!
Posted 72 months ago.
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We all need our hobbies Matt. I tend to peep up more about the 50mm/1.8 since that's often the next purchase.
Posted 72 months ago.
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