Question on flash

[yeocolin]

Hi,
I've got a question on flash usage. I hope you can answer it.

When I use flash on my Dynax 7 or Dynax 404si at A-priority at a fixed aperture size, the shuttle speed is 1/60s, irregardless if I point it to a bright or dark subject. However, when I use exposure lock, the shuttle speed changes according to brightness of subject.

I find this quite strange. If I shoot a dark subject in this way, will it turn out underexposed, since the shuttle speed is 1/60 irregardless of subject's brightness if I don't use exposure lock? Or does the camera actually change the power of the flash according to subject's brightness, such that although shuttle speed is at 1/60s, it will still be adequately exposed?

If my 1st theory is true, then it would also mean by exposure locking, thus changing shuttle speed according to subject's brightness, power of flash is probably constant, since exposure can be modified via shuttle speed.

 

[sulhan]

Hi Colin....


Since you have the dynax 7......you should be able to conduct the test without film. Just use the camera without film and shoot and see the data recorded in the memory.....

From there....you will be able to have a feel on what the camera is doing....

It would be an interesting experiment!!!!

regards,
me

 

[alvin]

My dynax 5 seems to set my shutter speed according to the focal length of the lens used. So when e.g. i'm @ 70mm, it's at 1/90, between 100-210 it's @ 1/125 (Metz32, no HSS, 70-210/4), at 50mm or less it's at 1/60 (50mm prime, or sigma 28-70mm)... regardless of what i point it at. aperture wide open.

i'm not helping but i wanna learn more too...

 

[alvin]

Shouldn't we put film in when using the flash? If I don't put flash, my flash will usually go off full blast. With film inside, it fires it "properly". So says my instruction manual...

 

[sulhan]

Hi COlin....

When you use a fixed aperture.....and the dedicated flash, the camera will allow you to take in aperture priority at 1/60. As for the 5600HS(D), if you zoom the lens say from 35 to 80mm...you can see the value change from 1/60 to 1/90.

THis means that there is actually a preset calculated values based on the flash zoom head in correspondence to the lens.

However, you question on over exposed or under exposed......flash power will be fixed BUT.....the timing at which the flash is triggerd by the electronics of the camera will correctly exposed the photo......

So ....from the camera 404si/Dynax7 yes the 1/60s is true for wide angle position...(In fact i also have these two bodies).......

Hope that answr your question........don't worry......the photos will be correctly exposed....


rgds,
me

 

[ming76]

hi colin
From what I know the syn speed( when flash is on without HSS) for minolta in P and A mode is 1/60 s. Thats why no matter what u focus at, the shutter is 1/60

The exposure lock button that u mentioned I think is also the spot metering button. And this funtion in A mode is suppose to create a balanced exposure between the background and the subject. Usually this function is use in low light condition.

If u are using a dedicated flash like 5600 or 5400 the flash output will vary according to the amount it recieved from the subject.

 

[yeocolin]

Thanks for all you guys' fast response. I'm sure the exposure is correct, because I had used my 404si to shoot wedding using slides and they were all correctly exposed. Since 404si has no HSS, I didn't suspect anything since I don't expect shuttle speed to be much faster. That's why I suspect the power of the flash is corrected according to exposure, like what ming76 mentioned, 3600HS and the built-in flash are dedicated flash (I'm using 3600HS for my accessory flash).

Nonetheless, I had a very bad experience when shooting with my extension tube and using flash to shoot insects. Shuttle speed was 1/60s and I happily shoot with slides. Later I realised all slides were underexposed. When I returned to shoot again with the same set-up, I realised when I use exposure lock, the shuttle speed actually changes, so I just keep using exposure lock and all my pictures were correctly exposed.

Anyway, when I tried to repeat the experiment again, there isn't such a problem anymore. ie shuttle speed changes according to subject brightness without having to press exposure lock. This is despite keeping all variables equal, except this time I'm doing this experiment in the day time, yesterday's experiment at night. Of course I'm not suggesting that this has anything to do with available light/daytime, but just thought its a strange observation.

Hope this isn't too much of a red herring to you.

Have fun!

 

[yeocolin]

Hmmm.. come to think of it, maybe the 'problem' surfaced cos I was metering at night. Even though the room's lamp was on, but it still can't be compared with sunlight illuminating the room, that's why I don't have this 'problem' now. Jerry and Danny from Minolta Yahoo groups also highlighted that exposure lock is also switching on slow sync, so maybe that's why there's a change in shuttle speed.

 

[deslim27]

Nonetheless, I had a very bad experience when shooting with my extension tube and using flash to shoot insects. Shuttle speed was 1/60s and I happily shoot with slides. Later I realised all slides were underexposed. When I returned to shoot again with the same set-up, I realised when I use exposure lock, the shuttle speed actually changes, so I just keep using exposure lock and all my pictures were correctly exposed.

Hi Colin, I just wonder what is the distance between your lens to the subject when you used a extension tube? Was your flash setup as remote unit?

 

[yeocolin]

For both instances when slides were underexposed and subsequent attempt when all slides were correctly exposed, distance from subject to lens from 1m to 40cm. On both instances, I used the flash on hotshoe directly, didn't use it as remote flash.

 

[TME]

Hmmm.. come to think of it, maybe the 'problem' surfaced cos I was metering at night. Even though the room's lamp was on, but it still can't be compared with sunlight illuminating the room, that's why I don't have this 'problem' now. Jerry and Danny from Minolta Yahoo groups also highlighted that exposure lock is also switching on slow sync, so maybe that's why there's a change in shuttle speed.

Colin, I think the main reason why the shutter speed stays at 1/60 when u do normal metering and 1/90 when u do spot-metering is that the u are actually using 2 different metering modes. The normal mode where u just point and meter would use the default centre-weighted metering or evaluative metering (14-segment honeycomb). Whereas when u press the AEL button, u are doing spot metering where the camera meters the spot in your frame that the centre focus sensor falls on.

So with evaluative and centre-weighted metering modes, the entire scene's light is taken into consideration mah..... so since the ambient light has not changed much, whether u aim at the sky or the object (both are lit by the same light source), the shutter speeds will not change. The flash can compensate for the slight change in illumination. (i..e the object will only be slightly darker and with the flash, the camera does not need to lower the shutter speed). However for spot metering, the ambient light is not factored in when u point at a specific object....... more so if the sensor is pointing at a shodowed part of the object... so basically in evaluative and centre-weighted metering, the camera's light meter tends to get fooled by the background light and underexpose the subject and correctly expose for the background.......

For your "experiment" in the day and night, the light source at night is inside your room and so it illuminates everything more or less equally. The difference in lighting is not significant and so the flash can compensate the difference. U can use the DATA function and check the honeycomb pattern which tells u the spots within the 14-segment that are exposed properly, under- and overexposed. In the case of the day metering, the light comes from outside the room, and probably casts significant shadows in the room even though the room may be bright to your eyes generally. The difference in lighting this time is probably significant enough for the camera to have to compensate by changing the shutter speed. The flash is of no use since if u are metering a bright spot (normal metering, not spot), then the shutter speed must drop to accomodate the increase in ambient light. If u meter a darker spot, then the shutter speed remains as 1/60s since the flash is now of use by lighting up the dark spot.

I hope this makes sense..... I used to have problems getting correctly exposed shots in the day when need to use flash...... cos the background lighting is always much brighter than my subject.. in the end I either spot meter or just +2-3EV so that my subjects' face is lighted properly.....

I'm pretty interested to test out what Zerstorer mention in the other thread that I started. He mentioned that with the TTL on the Dynax 7, with centre-weighted or evaluative metering modes, the camera will tell the flash to expose for the area that falls nearest to the focus sensor that is being used to focus in the frame. So if u have a bright background with a subject on the right of the frame, using the right-side focus sensor to focus the subject would mean that the camera meters for the background and exposes it correctly. This leaves the subject underexposed. But since the subject is at the right focus sensor, the flash will compensate by firing longer so that the subject is correctly exposed as well. In this case, both the subject and background are correctly exposed. So u have your cake and eat...... in any case, your subject must occupy at least 1/3 of the frame. Any comments or has anyone tried this? I'm not sure if the TTL of the program flash works this way or only for the higher end models?


Thanks!

 

[TME]

For both instances when slides were underexposed and subsequent attempt when all slides were correctly exposed, distance from subject to lens from 1m to 40cm. On both instances, I used the flash on hotshoe directly, didn't use it as remote flash.

Your tube might have obscured the flash beam..... U might need an extension for the flash so that it is not blocked by the lens? 1m to 40cm is quite near right?? Nto sure here lar... just guessing.........

 

[deslim27]

For both instances when slides were underexposed and subsequent attempt when all slides were correctly exposed, distance from subject to lens from 1m to 40cm. On both instances, I used the flash on hotshoe directly, didn't use it as remote flash.

Hi Colin,

I just checked 3600HS manual page E43, it wrote "If the subject is closer than 1m, use an off-camera flash with cable".

I believe your subject is too close for the flash coverage since it 1m to 40cm away from lens.

Even my 5600HS that can tilt 10 degree downward can cover to minimum 0.7m only.

If you like macro photography a lot, I think its worthwell getting a macro ring flash, the result should be better (but $$$$$ :sweat: $$$$$) haaaa..

 

[Zerstorer]

I'm pretty interested to test out what Zerstorer mention in the other thread that I started. He mentioned that with the TTL on the Dynax 7, with centre-weighted or evaluative metering modes, the camera will tell the flash to expose for the area that falls nearest to the focus sensor that is being used to focus in the frame.

Need to clarify that I'm not referring specifically to the Dynax 7. It's just a general comment on how matrix/multipattern TTL flash algorithms are supposed to work in such cases. I'm not certain of the exact implementation or effectiveness for the Dynax 7.

 

[yeocolin]

With reference to Deslim27 and TME comments, the extension tube shouldn't be the problem cos remember, I shot both times under the same circumstances (flash on hotshoe, extension tubes, same lens etc.). Only difference was I used AEL or not.

With reference to TME's earlier discussion on spot metering. In Dynax 7, AEL doesn't turn on spot meter as well, only Dynax 404si does that. In D7, AEL can work on honeycomb, centre weighted and spot meter.

Anyway, all these are not really of concern to me, other than for academic interests, cos in the end, I've managed to consistently correctly expose my subjects, be it night time or macro, even with slides, without exposure compensation.

I guess the key thing to learn from this discussion is that it pays to not shoot blindly, but look at the exposure data from time to time. However, the take home message is to know your camera body well. The same goes for digital camera because when taking important pictures, you may not have time to shoot the subject again.

 

[TME]

With reference to Deslim27 and TME comments, the extension tube shouldn't be the problem cos remember, I shot both times under the same circumstances (flash on hotshoe, extension tubes, same lens etc.). Only difference was I used AEL or not.

With reference to TME's earlier discussion on spot metering. In Dynax 7, AEL doesn't turn on spot meter as well, only Dynax 404si does that. In D7, AEL can work on honeycomb, centre weighted and spot meter.

Anyway, all these are not really of concern to me, other than for academic interests, cos in the end, I've managed to consistently correctly expose my subjects, be it night time or macro, even with slides, without exposure compensation.

I guess the key thing to learn from this discussion is that it pays to not shoot blindly, but look at the exposure data from time to time. However, the take home message is to know your camera body well. The same goes for digital camera because when taking important pictures, you may not have time to shoot the subject again.

Well-said! But hor when in the heat of shooting where got time to take a look at the data and think??? Just shoot lar..... then find out what went wrong later...... which is why going digital is such a pull for me........ kekeke....... can "semula" many times mah..... at almost no cost...... except for batteries lar.....