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標題: Edu-ma-cate me on flash [打印本頁]
作者: SmellyTofu    時間: 2008-4-15 17:26     標題: Edu-ma-cate me on flash

To put it bluntly.. so far, ETTL II on my 580EX suck like the proverbial... the biggest problem is using the 17-40 with the 5D and there's hot spots and what not (talking bouncing the light only)... I've got a "fake" Gary Fong lightsphere and it doesn't seem to help all that much except soften it. I tried it on manual mode (1:1) and it seems to really put on the charge and make a really big flash... comes out alright but haven't drive it in a high ceiling situation to really trust it... annnnyway....

What am I doing wrong? What can I do to make it look so nice like the Nikon SB800's that seem to be so deadly great every single time??
作者: shutterbug    時間: 2008-4-15 18:06

I don't understand what your problem is....so you're bouncing and you get hotspots?  That's pretty impossible unless your ceiling is very low and shiny....

Most of the time ETTL will underexpose not over...

And if you use manual flash, you should be able to do whatever SB800 can do.  Have you read a website that explained how ETTL works?  If not, I might be able to dig it up for you...
作者: SmellyTofu    時間: 2008-4-15 19:33

Yeah, I was working on the weekend... inside a chapel and it had relative high ceiling in flat white paint.. maybe 3.5-4 m high... but on 17mm (coz I had no room), the flash pointing up, all I see is a really bright spot on the ceiling where I've pointed the flash and the rest fairly dark.. I'll post a pic here tonight when I get home... I read a bit about ETTL but it just seems like it's the best setting to have but from my results, it doesn't appear that way.
作者: lerico    時間: 2008-4-15 20:21

Is there any high reflection object in the scene? mirror or chrome object usually throw off ETTL.

Since you are at 17mm full frame, is the ceiling in the photo too? and your flash is pointed up to the ceiling? Maybe that's why. ETTL sees the ceiling in the photo, and it thinks that that part is properly exposed, so it turns down the output.

ETTL always avoid ANY blown out highlights. That's why many people say it underexpose.

You should try using center average or spot metering, zoom-in to your subject, press the * button for flash exposure lock, then take your picture. In that case, under the same setup, you should see proper exposure for your subject (or whatever in your spot circle when you zoomed in and pressed FEL), and a blown out ceiling.

However, you should try to avoid blown out ceiling anyway. So in that case, I might avoid using lightsphere and use a home-made softbox/reflector that doesn't require a ceiling bounce.

Anyway... to conclude, from my experience, ANY highly reflective object will thrown off ETTL. Becuase ETTL always avoid highlight blown out. When that is the case, one must use either spot metering -> zoom in -> FEL method or set manual flash exposure.
作者: SmellyTofu    時間: 2008-4-15 22:22

Yeah, the ceiling was in part of the shot... maybe that's what I need to avoid.... but quite hard with 17mm...  my fd suggested I use spot and then FEL.. never really used that one b4.. but I'll see how I go with it.
作者: shutterbug    時間: 2008-4-15 23:55

if you're in a rush...shoot a frame then dial in flash compensation...

it's better to overexpose a bit than underexpose
作者: SmellyTofu    時間: 2008-4-16 01:41

OK.. here's the shots.. pls don't worry about the actual composition of it as these are off-shots.
作者: shutterbug    時間: 2008-4-16 07:20

The pics seem normal to the settings you have, the bright spot is normal because that's where your flash is aiming, and the dark area is normal too because the flash falls off and the place seems to be pretty dark.

There are many way to fix this situation though.
作者: lerico    時間: 2008-4-16 08:09

Definitely it is the white ceiling, light brown wall WITH dark dressed people and dark carpet that thrown off ETTL.
作者: echo    時間: 2008-4-16 14:50

你第二張相既主體曝光都係正確. 至於第一張就 UNDER 左,  ETTL 想準最好就用 FEL LOCK, 問題係FEL LOCK 又要PRE FLASH 又要構圖, 好多野都係一閃即逝. 對於移動物體作用不大.

兩張相就算用 FEL lock 都係冇得救. 加大閃燈 OUTPUT, 背景係會光左, 但主體 OVER, 你點揀?

而且 17MM + 5D, 根本580 唔可以 COVER 到 !! 直打都未得, 更何況 BOUNCE???

想要背景光D? 用機頂燈係呢D 場合打  bounce? 唔係唔得, 不過好難打得靚. 長方形場地, 後面夠光前面爆!

SB800 係好野架, 你用咩 MODE??

由550 時代已經投訴 CANON D FLASH 唔得, 580 話配合原廠鏡會自動配合距離去計算OUTPUT. 不過 " BOUNCE" 除外.
作者: Catpiano    時間: 2008-4-16 16:48

Those pics .. look normal to me too ..   

Of course .. you could do better ..  say if u could add a second flash ..  or change the bounce direction .. or not using bounce at all? but direct flash with diffusor ?

Or set higher iso ..  so less output from flash .. or just crop the bright area law ..

I am sure even with D300 + SB800 .. result will be more or less the same ..

[ 本帖最後由 Catpiano 於 2008-4-16 16:50 編輯 ]
作者: chobit    時間: 2008-4-17 11:27

I think the LSII should help in your situation.  Also I don't always point the flash up in those situation...!  For example on your 2nd photo.  You may try point up, but angle it a bit to the right-rear.
Also, mix it up with higher ISO and large aperture sometimes help balance it out.

PS:  Can u share more on your setting?  Camera/ISO/Aperture/Shutter, etc..

EL

[ 本帖最後由 chobit 於 2008-4-17 11:29 編輯 ]
作者: SmellyTofu    時間: 2008-8-10 15:04

OK... update... did another wedding on the weekend. During the indoors, I floated around the ISO1000-1600 using manual setting. Mainly around f5.6-6.3 and 1/30-1/50s with -1 to 0 FEC with the Tamron 28-75 (yeh yeh, need to get 24-70L soon)... They looked sharp enough but just worried it might be even too grainy on a 5D.

The unfortunate thing was during the banquet at night, the venue had varying ceiling heights in black so a lot of combinations just simply did not work consistently so my friend with the Nikon D3 + SB800 had to do the standard table shots (which I normally cover). (There was a guy with a SB900 and it seemed like the image was just slightly brighter but refresh rate is very fast.

Something that I might have discovered is that because I hang my 2nd (old) 10D body with the 420EX there that putting it on slave mode and making it fire whilst it's at my waist height spreads the light more.. but I'm not 100% sure if it's just useless hanging there or it really works well all because of the ceiling height variations.

Mind you, in something different.. it was pretty depressing that everyone at the banquet at night were using Nikons... GRRRRRRRR! HURRY UP CANON!!!

[ 本帖最後由 SmellyTofu 於 2008-8-10 16:15 編輯 ]
作者: chobit    時間: 2008-8-12 01:25

I am not sure if I've ever mention.  On Canon system, I personally like using using Average instead of Evaluative for the flash setting, as I found it more consistent.

When using indoor and having the flash being the main light source.  FEC at +2/3 works best

When doing fill flash outdoor w/o strong back-lite.  Then I use FEC at -1 stop.
作者: SmellyTofu    時間: 2008-8-12 01:40

原帖由 chobit 於 2008-8-12 02:25 發表
I am not sure if I've ever mention.  On Canon system, I personally like using using Average instead of Evaluative for the flash setting, as I found it more consistent.

When using indoor and having th ...


Yeah, I found out average is becoming my default setting where it was on evaluative beforehand. I think now my photo partner hopefully won't scold me for giving him such crappy photos to edit.. all I need to do now is WB control and making the lighting more natural..  Maybe it's a Lightroom thing but it seems like when you load it, they apply this default setting that makes indoor shots look really weird in colour.
作者: SmellyTofu    時間: 2008-9-28 18:00

OK.. did another job last night.. and I used a 580EX2 on the 5D and 580EX as a slave... and what I've found is that at close range it's not too bad, but at longer distance like in a Chinese restaurant, it's still not acceptable... short of scattering flashes all over the restaurant.

Techniques I've been using is to crank up ISO to around 1000-1600 (reluctant to use 3200).. Manual mode and for a lot of the time hovering around f4-5.6 and 1/40-1/60.. still... AHH! it's really giving me the shxts actually...

[ 本帖最後由 SmellyTofu 於 2008-9-28 19:05 編輯 ]
作者: chobit    時間: 2008-9-28 21:40

Show us some samples if you can.  However, please understand that there is a limit of what a single or even 2 flashes can do.  Then, I suppose it depends on what you have in mind for the end results.
作者: SmellyTofu    時間: 2008-9-29 03:15

Here's some samples.. again, these are off-shots so please ignore the composition of it but these are pretty much out of the camera and converted from Lightroom. All these were bounced off the ceiling which was yellowy in colour so I've only fiddled with the WB.

1st pic, f7.1 1/80 ISO1600
2nd pic, f7.1 1/50 ISO1600

[ 本帖最後由 SmellyTofu 於 2008-9-29 04:17 編輯 ]
作者: SmellyTofu    時間: 2008-9-29 03:17

Double post.. pls delete

[ 本帖最後由 SmellyTofu 於 2008-9-29 04:19 編輯 ]



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