Regarding Shutter Speed
- Thread starter tappy
- Start date
You got it wrong. Worse still, you dispensed the error as advice.
Either clarify yourself properly, or admit you made a mistake and move on. No need to get upset about it.
we all do make mistake at some point of time,
the most important thing is we acknowledge our mistake and learn from there,
nobody is perfect..
let's move on.
the most important thing is we acknowledge our mistake and learn from there,
nobody is perfect..
let's move on.
as for why/how HSS can be used...
1: higher shutter speeds. (like duh)
2: wider apertures for shallow DOF.
many more uses really. but offhand i can think of this 2 practical applications
1: higher shutter speeds. (like duh)
2: wider apertures for shallow DOF.
many more uses really. but offhand i can think of this 2 practical applications
The shutter opening time is determined by:
1. The time needed for the flash light to travel to the subject and back to the sensor.
2. How well the mechanisms of the shutter button, shutter operation, the flash trigger circuitry, the flash response work in unison.
The second item can never be predicted with absolute accuracy. There's age to consider and it becomes impossible to know.
If you could, you would be able to design your camera to fire the flash, wait x millisecond for the flash to fire, wait y microsec for the light to return, open the shutter z milliseconds ahead of the light reaching the shutter so that is open when the light arrives and take the picture with a shutter speed appropriate for the brightness and aperture. If you misjudge x or y or z, you get nothing and is probably all the time.
Solution is a compromise, keep the shutter open long enough to cover x, y and z plus some extra to factor for the unpredictable delays of the real world and use the aperture to control the light falling on the sensor. Modifying the shutter speed risks missing the flash return window.
Flash power does not make light travel faster, further yes as there's more that can be lost and still be bright enough. Light brightness falls off as a function of the square of the distance (d to the power of 2), twice the distance, brightness becomes 1/4.
A brighter, more powerful flash gives you more latitude with smaller aperture settings and further subjects, the smaller aperture gives you more DOF that a weaker flash can't.
1. The time needed for the flash light to travel to the subject and back to the sensor.
2. How well the mechanisms of the shutter button, shutter operation, the flash trigger circuitry, the flash response work in unison.
The second item can never be predicted with absolute accuracy. There's age to consider and it becomes impossible to know.
If you could, you would be able to design your camera to fire the flash, wait x millisecond for the flash to fire, wait y microsec for the light to return, open the shutter z milliseconds ahead of the light reaching the shutter so that is open when the light arrives and take the picture with a shutter speed appropriate for the brightness and aperture. If you misjudge x or y or z, you get nothing and is probably all the time.
Solution is a compromise, keep the shutter open long enough to cover x, y and z plus some extra to factor for the unpredictable delays of the real world and use the aperture to control the light falling on the sensor. Modifying the shutter speed risks missing the flash return window.
Flash power does not make light travel faster, further yes as there's more that can be lost and still be bright enough. Light brightness falls off as a function of the square of the distance (d to the power of 2), twice the distance, brightness becomes 1/4.
A brighter, more powerful flash gives you more latitude with smaller aperture settings and further subjects, the smaller aperture gives you more DOF that a weaker flash can't.
I just learnt this today on how to apply this in a dark scenario rather than in bright sunlight which was how it was being taught in some training video.
Very useful.
Especially for point 2.
However, I still have a question in mind. If the shutter speed is too high for ambient, will I still be able to capture blur image circles of small lights such as candles flames and tiny light bulbs that are in the background of the subject?
Using fast shutter speed in dark environment? How did that turn out? Any photo to share?
I'm sorry, but these factors have very little relevance to the max sync speed limit of a camera.
1. At normal flash distances (say 15m or less) light travels to the subject and back in 100 nanoseconds or less - that's pretty much irrelevant as far as DSLR systems go.
2. Shutter lag is compensated for because the flash only fires when the 1st curtain is fully open.
For focal plane shutters, max sync speed is primarily limited by curtain speed.
- let's say your curtains can travel completely across the frame in 1/300s (3.33ms)
- at a shutter speed of 1/250s (4ms), the 1st curtain would be across the frame, leaving the frame fully open for 0.67ms (4 - 3.33) before the 2nd curtain moves
- the flash has to fire within this 0.67ms window, including flash trigger lag and entire flash duration. Manufacturers normally include a buffer when rating max sync speed (my old Canon 30D could sync at 1/300, faster than its 1/250 rating)
- if the shutter curtain is slower, and can traverse the frame in, say 1/230s, the manufacturer might rate the max sync speed at 1/200 or 1/160
- with some more powerful, longer duration studio strobes, it's better to set a lower sync speed, cause the flash duration can be quite long compared to shoe-mount flashes
- flash trigger can be delayed with some wireless triggers, which again can normally be compensated for with a slower shutter speed
This explanation is probably hard to understand if you don't understand how focal plane shutters work. It's easier with diagrams -- there are some animations around the web that show the sequence.
1. At normal flash distances (say 15m or less) light travels to the subject and back in 100 nanoseconds or less - that's pretty much irrelevant as far as DSLR systems go.
2. Shutter lag is compensated for because the flash only fires when the 1st curtain is fully open.
For focal plane shutters, max sync speed is primarily limited by curtain speed.
- let's say your curtains can travel completely across the frame in 1/300s (3.33ms)
- at a shutter speed of 1/250s (4ms), the 1st curtain would be across the frame, leaving the frame fully open for 0.67ms (4 - 3.33) before the 2nd curtain moves
- the flash has to fire within this 0.67ms window, including flash trigger lag and entire flash duration. Manufacturers normally include a buffer when rating max sync speed (my old Canon 30D could sync at 1/300, faster than its 1/250 rating)
- if the shutter curtain is slower, and can traverse the frame in, say 1/230s, the manufacturer might rate the max sync speed at 1/200 or 1/160
- with some more powerful, longer duration studio strobes, it's better to set a lower sync speed, cause the flash duration can be quite long compared to shoe-mount flashes
- flash trigger can be delayed with some wireless triggers, which again can normally be compensated for with a slower shutter speed
This explanation is probably hard to understand if you don't understand how focal plane shutters work. It's easier with diagrams -- there are some animations around the web that show the sequence.
Kevin, you want to see some night macro shots is it? :think:
orrrhhhh.... night macro har...?
ok ok I understand now.
Exactly what I wanted to say. The limitation of flash sync speed is caused by focal plane shutters.
Also note that when taking flash photography, as long as you're below the max flash sync speed, the shutter speed does not affect the exposure of the subject, it only affects the exposure of the ambience. This is because typically the flash duration is very short, e.g. 1/880s (full power) - 1/38,5000s (1/128 power) for the Nikon SB-900. So for example, if you're shooting at f/8 with full power flash output from the SB-900, the subject is exposed at f/8, 1/880s regardless of whether you're using 1/250s or 1/30s for the shutter speed.
These are the factors that affect the exposure of the subject:
- iso, aperture, flash to subject distance, flash power output
And these are the factors that affect the exposure of the background:
- iso, aperture, shutter speed. Of course if the background is close enough the spill from the flash will have an effect as well.
The proper way to use a flash is first to meter the ambience, select the desired exposure accordingly by setting the iso, aperture & shutter speed, then either use TTL or manual flash to fill the subject. For example, here is normally what I would do:
- meter the scene, then decide how many stops I want to dim the background.
- e.g. if at iso 800, the meter says f/8, 1/30s, and I decide to dim it by 2 stops, I would set the camera to manual mode, f/8, 1/125s
- switch flash to TTL mode, take note of the min & max shooting distance, then start taking pictures by ensuring that the subject is within that distance.
- note that each time you change the aperture/iso/focal length, the min & max shooting distance will change.
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The sync speed is what it is because the manufacturer has to pick a speed to accommodate all the components.
In this case (at this time), as you have stated, is the shutter; accommodate this and the rest falls into place.
I believe we're saying the same - "....keep the shutter open long enough to accommodate x, y and z......"
You articulated it very well. :thumbsup:
May be I can add on abit. At higher than the x-sync speed, the 2nd curtain closes before the 1st curtain is fully open. Normal flash will hence not illuminate the entire frame as at any time only a horizontal strip of the frame is exposure. This is where HSS comes in.
spgohjc said:
Ah I forgot to add I'm using auto FP. HSS for canon. I try to upload some pics later. Although these test shots were not abt achieving low DOF but more on how shutter speed will affect the picture as we increase it faster from the fastest sync speed with Auto FP & HSS.
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