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Old Aug 9, 2009, 2:51 PM   #1
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Default How to use a 1/40000 shutter speed? - Casio EX-F1

I just got a Casio EX-F1 this weekend and I've been playing around for a while. They sell it as able to take shots with a 1/40000 shutter speed however when you try to use that speed, even with ISO 1600 and daylight everything is so dark that it's totally unusable.

I mention 1/40000 because that's the maximum the camera offers, but the problem is still present with 1/20000 and much lower!!

Q1- Is there a way to be able to use that shutter speed and get proper pictures? If there isn't, not really sure at the moment why it's in the camera in the 1st place...

I thought that maybe the problem could be sorted by using the built-in/external flash but if you enable it, then the maximum shutter speed becomes 1/1000.
Q2- I'm a beginner, but is it easy to explain why the shutter speed is limited so much when you enable the flash?

Thanks guys!
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Old Aug 10, 2009, 6:04 AM   #2
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You'll need a higher ISO speed, more light, and a wider aperture. With your camera, the lens is brightest on it's widest end (don't zoom in as much). You'll also need to shoot in manual exposure mode (setting the aperture and shutter speed).

If you try to use a shutter speed that's too fast for the widest available aperture (smaller f/stop numbers), lighting and ISO speed set, you'll get an underexposed (too dark) image.

You have 4 main variables to take into consideration for exposure (and I use the term "main" since there are a lot of nuances to how you measure the light (for example, your metering mode), as well as different film characteristics if shooting film, and camera settings if shooting digital for the desired tone/contrast curve within an image and more). Once you have a better idea of how these 4 variables work together to give you a properly exposed image, the other fancy features will make more sense. These variables are light, aperture, ISO speed and shutter speed.

Light is typically measured as EV for Exposure Value in Photography.

Aperture (which works similar to the pupils in your eyes, where you can open up the aperture iris wider to let in more light, or close it down to let in less light). If you let in more light with a wider aperture, you can expose the film or sensor faster. If you let in less light with a smaller opening, it takes longer to expose the film or sensor. Note that aperture is normally expressed as f/stop, which is a ratio between the focal length of the lens and the diameter of the aperture iris. So, smaller values represent a larger iris diameter.

When you vary the aperture, you're controlling the iris in the lens (which like a pupil in your eye, can be opened up to let in more light or closed down to let less light in). So, this impacts the shutter speeds you'll need for proper exposure (since more or less light is getting through to the sensor). Aperture also impacts Depth of Field.

The aperture scale in one stop increments (with larger than f/1 apertures possible but very rare in lenses) goes f/1.0, f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8.0, f/11, f/16, f/22... With each one stop move to a smaller aperture (represented by higher f/stop numbers), you will need shutter speeds twice as long for proper exposure for the same lighting and ISO speed (only half the light gets through compared to a one stop larger aperture).

ISO speed. This is how sensitive the film or sensor is to light and is the same thing as the older ASA rating for film. The higher the ISO speed, the faster you can expose it (each time you double the ISO speed, you can use shutter speeds twice as fast for the same lighting and aperture.

Shutter Speed is how long the camera's shutter stays open to expose the film or sensor).

IOW, it all boils down to how sensitive the film or sensor is to light (which you control via the ISO or ASA speed of the film you use with film, or the ISO speed settings you use with digital), and how much light you need to let it see to "expose" the image (which you control via the aperture opening size and shutter speed).

These exposure calculators and simulators may help you understand it better. But, you'll need to be in brighter lighting, and using a higher ISO speed, and using a wider aperture to get shutter speeds anywhere near 1/40000 second. Is there a reason you need shutter speeds that fast?

http://www.robert-barrett.com/photo/...alculator.html

http://www.photonhead.com/simcam/shutteraperture.php

Note that aperture also influences depth of field. See this handy calculator for more information about it:

http://www.dofmaster.com/dofjs.html

As for using a flash, chances are, the flash duration is too long to use shutter speeds that are too much faster due to mechanical constraints (opening and closing aperture or shutter).
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Old Aug 10, 2009, 10:57 AM   #3
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Good post JimC, but I will take issue with part of it:
Quote:
Originally Posted by JimC View Post
...
As for using a flash, chances are, the flash duration is too long to use shutter speeds that are too much faster due to mechanical constraints (opening and closing aperture or shutter).
Everything I have read about strobe flash (as opposed to flash bulbs or flash powder) says that unless there is paint pealing power, the flash duration is 1/1000 or faster. The problem with chemical cameras with focal plane shutters was that though all parts of the sensor (film) was exposed for (e.g.) 1/500 second, not all parts were exposed at the same time. That is the same issue with the way many/most/all digital cameras move the data from the sensor to memory - or how they "freeze" the image.

More likely that the limit of (e.g.) 1/125 sec shutter speed syncing with flash is that is how long it takes to extract data from the whole sensor.

The old "in the lens" shutters (for large format and some medium format chemical cameras) synced happily up to 1/500th sec.
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Old Aug 10, 2009, 11:28 AM   #4
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For whatever reason, Casio limited the fastest shutter speed you can use with flash to 1/1000 second.

Typically, the flash duration is going to be somewhere between 1/10000 second and 1/1000 second (although with some flashes, it may drop a bit slower than 1/1000 with a full strength flash).

So, if you tried to use a flash at 1/40,000 second, your shutter speed is going to be faster than the flash duration with many flashes (causing an underexposure problem if a full duration flash is needed). The problem with this particular Casio model may or may not be a mechanical issue (which was my best guess). But, you'll often see shutter speed limitations imposed because of the aperture/shutter design (some P&S models use the aperture as a shutter), if the design was such that the manufacturer decided to use a mechnical versus electronic shutter in some condtions).
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Old Aug 10, 2009, 3:02 PM   #5
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Quote:
Originally Posted by JimC View Post
Is there a reason you need shutter speeds that fast?
Many thanks for the explanation Jim!.

I was asking just about 1/40000 because that's the maximum the camera was offering and I could not think about a human way to be able to use that shutter speed.

I've been trying today with some speeds I'd really like to use in order to freeze movement (kind of 1/2000, 1/3200, 1/4000 & 1/6400) and even with the wider aperture (f2.7), ISO 1600 and daylight the pictures were so dark that they were unusable.


I've been now reading this article

http://pixsylated.com/2008/12/smashi...-light-part-2/

where the photographer had to use 12 speedlights in order to get the right light at 1/6400. Could this be done (albeit with a worse quality) with the built-in settings?


Quote:
Originally Posted by JimC View Post
So, if you tried to use a flash at 1/40,000 second, your shutter speed is going to be faster than the flash duration with many flashes (causing an underexposure problem if a full duration flash is needed).
Yeah, we may have an underexposure if the full duration of the flash is needed but if the flash lasts much longer than the shutter speed, I was thinking that (at least) this would help a little with the light, right? Even if they fire the flash before the shutter is opened and closed, the whole picture would benefit from this, wouldn't it?

Last edited by spanish_biker79; Aug 10, 2009 at 3:10 PM.
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Old Aug 10, 2009, 3:18 PM   #6
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The duration of the flash is the way you vary flash power. So, if your shutter speed is faster than the flash duration, you're going to get underexposed images unless you have enough ambient light to make up for the lack of flash power.
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Old Aug 10, 2009, 3:39 PM   #7
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Thanks!! I'll keep reading to understand a little bit more. This is quite complex!!
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Old Aug 10, 2009, 5:18 PM   #8
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Oops - I read 1/40000 as 1/4,000: just a factor of ten off.

Though I still suspect that shooting at that speed (1/40,000) with flash duration less than that would likely give a narrow band of properly exposed image instead of an underexposed whole image.
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Old Aug 10, 2009, 5:53 PM   #9
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My understanding was that the flash duration (whatever that is but around 1/1000? ) is much higher than 1/40,000, hence the shutter closes before it receives all the light it needs to take a proper picture as it would just use 1/40,000 of the flash (whilst the shutter is opened) and all the rest would be wasted.

Not sure if this is right though, it's my understanding so far...
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Old Aug 11, 2009, 3:02 AM   #10
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In general you are going to need very strong light for that kind of shutter speed. Also normal flashes are not going to be fast enough.

You will need strong direct lights.

Shutter speeds that high are usually useful only in a very specific set of circumstances - like those shots of bullets going through apples and exploding balloons filled with water.
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