Shutter speed in low light. Camera: AV, flash: ETTL

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In camera AV mode with flash unit set to ETTL + HighSpeed help against 
overexposure, changing the time to shorter than 1/200, it works great.

But there is another problem, in low light camera want set time e.g. to 1/10 - 
1/30 and photos are bad blurry. Then must turn camera to M mode, or flash to M, 
and start adjustment.

In camera Av mode, flash ETTL mode i would like to 400plus set time 1/200, when 
time calculated longer than 1/200. Then camera flash correction should be 
enough adjustment. Somtimes default 1/200 is to short, in 400plus menu should 
be choice shutter speed for Av mode. This would solve the problem.

Thansk for 400plus! :-)
Best regards
Piotr

Original issue reported on code.google.com by webw...@gmail.com on 24 Jan 2013 at 1:54

• Merged into: #70

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Original comment by eduardo....@gmail.com on 24 Jan 2013 at 4:56

• Changed state: Merged

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Hello again, one option "Lock time: 1/200 in Av mode" will be fully 
satisfactory for me. I think more users will be glad :-)

Original comment by webw...@gmail.com on 25 Jan 2013 at 2:50

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A locked shutter speed in Av mode... isn't M mode? If the camera determines 
that 1/200 is not enough for the current aperture + ISO, forcing that speed 
does not produce underexposure?

Original comment by eduardo....@gmail.com on 26 Jan 2013 at 7:19

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Of course, you are right, only "Lock time 1/200" == M mode, and does not make 
sense create 400plus option. Auto increasing ISO is great function but in low 
light increase to 1600 gives noise.

But as i mentioned in the first post i would to have something analogously to 
Speedlite HighSpeed option, there if needed camera calculate time shorter than 
1/200 (up to 1/4000), and automatically accordingly reduce flash power.

New 400plus function "Auto adjust flash power", could be calculate time 
difference between the originally camera time and MAX fixed time, and 
automatically accordingly increase flash power. 

Run only when camera calculate longer than 1/200
Option: set fixed time (range 1/45-1/200)

What do you think about this function?

Original comment by webw...@gmail.com on 27 Jan 2013 at 7:15

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Sorry, but I do not get it... probably my own fault, however, as I do not own 
an external flash (and try to use the internal one as little as possible); but 
the fact is that I do not understand this request.

Original comment by eduardo....@gmail.com on 28 Jan 2013 at 7:36

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Camera canon 400d: Av mode
Flash 430EX II Speedlite: ETTL mode

***

A. bright room, lens: f/2,8 - as example High Speed use

Example 1 - High Speed Sync OFF
camera set time: 1/200
results: 
---> shaken: NO
---> exposure: OVER

Example 2 - High Speed Sync ON
camera set time: accordingly to bright in room e.g. 1/750 (up to 1/4000)
results:
---> shaken: NO
---> exposure: CORRECT

***

B. dark room, lens: f/5,6 - does not matter is High Speed ON or OFF

Example 1
camera set time: accordingly to bright in room e.g. 1/10 (or longer)
results:
---> shaken: YES
---> exposure: CORRECT

***

C. dark room, lens: f/5,6 - idea

Example - idea of "Auto Adjust Flash Power" ON

-> option: set fixed time AAFT default 1/60 (range: 1/45, 1/60, 1/90, 1/125, 
1/180, 1/200) 

-> when works: only when camera in Av mode set time longer than user set in 
AAFT option

-> how works: get camera time that was accordingly set to bright (e.g. 1/10), 
next calculate difference with AAFT time (1/60), then for take picture set AAFT 
time (1/60) and increases the power of flash (in percentage).

results:
---> shaken: NO
---> exposure: CORRECT

Did you understand the concept, now? :-) This would require tests and algorithm 
percentage strengthening the flash power, but results may be promising. 400plus 
auto increasing ISO is great function but in low light increase over ISO 800 
gives noise. I would auto increase flash power if possibility.

Original comment by webw...@gmail.com on 28 Jan 2013 at 10:31

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When the camera decides that a certain exposure time is needed, it is aiming 
for a correct exposure of the background; because it assumes that the flash 
will only illuminate the foreground. In Av, Tv, and M modes, Canon EOS cameras 
work always in fill-flash mode.

So, unless you have a "flat" scene (composed only of close objects), raising 
the flash power is not going to compensate for a shorter exposure time. In a 
"normal" scene (a portrait in a dark room, for example) raising the flash and 
lowering the exposure time will only overexpose the foreground, leaving the 
background underexposed.

Agreed?

The 400D has a custom function to fix the shutter speed at 1/200s in Av mode 
when using a flash; some higher-end cameras have an option to limit the range 
from 1/60s to 1/200s, too. That looks close to what you are requesting, but 
look at what is written in the 5D3 manual:

"1/200-1/60 auto: Prevents a slow shutter speed from being set in low-light 
conditions. It is effective for preventing subject blur and camera shake. 
However, while the subject will be properly exposed with the flash, the 
background may come out dark."

Original comment by eduardo....@gmail.com on 28 Jan 2013 at 11:07

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I think "1/200-1/60 auto" from 5D3 is exactly the function i would like to 
have. Maybe can do new 400plus function without the difficult percentage 
algorithm, but by way of replace time longer than 1/180 to 1/180 with increase 
flash as follows:

when Av set 1/4 - 400plus change time to 1/180, increase flash +2
when Av set 1/6 - 400plus change time to 1/180, increase flash +2
when Av set 1/10 - 400plus change time to 1/180, increase flash +2
when Av set 1/15 - 400plus change time to 1/180, increase flash +1 1/2
when Av set 1/20 - 400plus change time to 1/180, increase flash +1 1/2
when Av set 1/30 - 400plus change time to 1/180, increase flash +1 1/2
when Av set 1/45 - 400plus change time to 1/180, increase flash +1 1/2
when Av set 1/60 - 400plus change time to 1/180, increase flash +1
when Av set 1/90 - 400plus change time to 1/180, increase flash +1
when Av set 1/125 - 400plus change time to 1/180, increase flash +1/2

How do you think, is it possible? If in 5D3 is prevent Av mode time function, 
that seems it needed. 

The sample values, after fast tests. Maybe values should be as table in txt 
file for include. Then everyone will be able to put your own times and flash 
increasing values.

Original comment by webw...@gmail.com on 29 Jan 2013 at 8:20