Flash Cs6 Serial Number For Mac
Lee Stlaurent
Is it correct? If it is could someone please explain why ISO is related to guide number in this way. The formula in wikipedia article about guide number does not have ISO in it so I wanted to know if the one I found is the right one and why.
The formula you've given is incorrect, at least for "straight" values of ISO numbers. ISO is related to sensitivity in that each stop in increased ISO is the same as a single stop of increased aperture. That means that to get ISO 200 guide numbers from ISO 100 numbers, you multiply by the square root of two, just as increasing aperture by that factor is one stop. Quadrupling the ISO doubles the guide number, and so on. Or, expressed the other way around in the equation, as in your formula: the guide number required for a given aperture and distance goes down by a factor of about 1.4 for every stop of increased ISO.
This formula tells you what GN you'll need from your flash at that distance and with those settings. You can also rearrange the terms; for example, if you have a basic flash with a fixed guide number, and your subject distance is also fixed, you might want to put those terms on the same side, so you can just calculate some number on that side:
Also be aware that halving flash power decreases guide number by, again, a factor sqrt(2). So, if your flash in my example above has the typical fractional power adjustment, and you set it to 1/4 power, the GN becomes 12m, so f/4 at ISO 100.
As a photographer, my first worry would be how far my flash light will be able to fire. If my flash has a rated GN of 40 mtrs, for ease of calculation we can know that at 10 metres i would need an aperture of f/4. GN/Distance = Aperture. If my subject is at 5 metres, i can shoot at an aperture of f/8 (40/5 =8).
The original post is asking for a quantitative relationship, not a series of examples. There is nothing wrong about the basic guide number relationships used in the above answers, but the quantitative relationship between Guide Number and ISO is
Again though, you are still not comparing like with like. The flashgun has a reflector built in as part of the assembly, and is quite likely to be the way it is used a lot of the time. The studio strobe is extremely unlikely to be used with just a "bare bulb". So, yes, you could do that comparison and get numbers from it, but as soon as you start using the equipment the first thing you will do is throw something on the front of the studio light. If it is a reflector, then the light reaching your subject will be increased, yet your flashgun would stay the same.
A far better comparison would be to fire them both into an umbrella and bounce the light back from that, or otherwise set them up as you would actually use them, to light the same subject the same way. Perhaps strap both into the same softbox for instance.
Of course a simple comparison of strength is not the only thing you need to consider. If you fire a flashgun into a large softbox, for example, you are unlikely to get as even a spread of light as you would with a studio strobe, because the reflector built in to the flashgun would concentrate the light more in the middle . So there is a quality of light difference to consider as well, and I don't mean high or low quality here, just difference. You may want the less even light for the shot you are taking, as you might if using a beauty dish with a honeycomb centre and diffuser outer ring.
The key thing here is that they are different, not just simply more or less bright, and you will be adding modifiers to them both probably anyway. There is no simple answer to how many watt/seconds = what GN. For one thing different studio strobes will give different outputs of light for the same watt/seconds rating, depending on other factors such as efficiency and flash duration. A GN measures the light itself, but w/s measures the power being used and not the actual light emitted.
All you can do is take a rough approximation for comparison purposes, and you have that already. Yes, it is simplistic, but to get into specifics involves so many variables and even then would only be relevant when using specific strobes with specific modifiers, as soon as you change to a different modifier the equation goes out of the window. LIKES 0 LOG IN TO REPLY
SkipDSkipDCream of the Crop20,476 posts
Likes: 165
Joined Dec 2002
Location: Southeastern WI, USAMore info Dec 07, 2013 08:19 #6
The simple answer is NO.
Studio flash units have a wattsecond (Ws) rating which is nothing more than a measurement of the electrical power that is stored in its capacitor(s) to power the flash tube. The actual light produced varies based on many factors including the flash tube itself, electronic circuitry in the unit, the reflector used to direct the light (if used), and, of course, any "modifiers" (such as an umbrella, softbox, etc.) which may be used. You can compare the light output from several different brand/model 320ws rated studio flash units - measuring the light output at the same distance with a flash meter - and you'll find variations between them that could be significant.Skip Douglas
A few cameras and over 50 years behind them .....
..... but still learning all the time.
It is an 'industry standard' for studio flash expressions of 'power' (the measurement of electrical energy), not expressions of 'light output', as Skip has already expressed. Since so many factors affect the conversion of stored electricity to amount of light falling upon the subject, the rather universal statement of electrical power was adopted.
I had reported comparative light output a few years ago:
Dynalite M500 (500 w-s) using a single Dynalite 2040 head which spreads light across a 140 degree wide area:
I use a 580ex ii speedlight and I understand the GN with flash head zoomed to 105mm at ISO 100 is 190. My question is how do I determine the GN for the other zoomed distances (24, 35, 50, 80)? In other words how did you know your 600ex-rt zoomed to 35mm has a GN of 110. Thank you for sharing such awesome information on this site.
I'm looking for a way to mark the drives digitally (for example with a UUID) so I can perform various actions with the drive while having the serial numbers intact. Hopefully also have other people use and format the drives, still allowing me to read the serial number off of them later.
This generates a UUID, calculates a CRC sum of that UUID, leaves just 8 first characters of that sum (because the length can vary and we need a constant length to effectively search for the pattern later). Then it concatenates that with some markers that can be used to extract the number form a data stream and verify if it wasn't damaged.
Keep in mind that if _myValue is of type int or uint, then (_myValue is Number) will also equate to true. If you want to know if _myValue is a number that isn't an integer(int) or unsigned integer (uint), in other words a float, then you can simply modify the conditional as follows:
It uses Number(_myValue) to cast _myValue to the Number class. If Number is unable to convert it into a useful number it will return NaN, so we use !isNaN() to make sure the returned value is not "not a number".
Some drivers of the USB disks does not expose the manufacturer serial number on the Win32_DiskDrive.SerialNumber property, so on this cases you can extract the serial number from the PnPDeviceID property.
As I mentioned in the DIY Alphabet Flash Cards post, Bella has really excelled in her learning using a variety of tools such as her Ikea chalkboard that I use to draw the alphabet, numbers, colours, and shapes on as well as the Munchkin bath letters and numbers that turn bath time into learning time too and flash cards like these DIY Number Flash Cards I am sharing with you today!
The guide number system, which manufacturers adopted after consistent-performing mass-produced flashbulbs became available in the late 1930s, has become nearly superfluous due to the ubiquity of electronic photoflash devices featuring variable flash output and automatic exposure control, as well as digital cameras, which make it trivially easy, quick, and inexpensive to adjust exposures and try again.[3] Still, guide numbers in combination with flash devices set to manual exposure mode remain valuable in a variety of circumstances, such as when unusual or exacting results are required and when shooting non-average scenery.
Different models of flash devices available on the market have widely varying maximum-rated guide numbers.[note 3] Since guide numbers are so familiar to photographers, they are near-universally used by manufacturers of on-camera flash devices to advertise their products' relative capability. However, such a practice demands industry-wide standardization of both the ISO setting and illumination angle underlying the ratings; this has only been partially realized. For the most part, manufacturers state guide numbers relative to a sensitivity of ISO 100.[4] However, manufacturers sometimes rate guide numbers at ISO 200, which makes them 41% greater.[5] Furthermore, the illumination angles underlying manufacturers' ratings vary greatly, which can make it particularly difficult to compare models.
It is easy to use guide numbers to calculate either an aperture or a flash-to-subject distance. Consider a flash device with a rating of 28 meters (which might be marked "92 feet", "28 DIN", "28/92", "92", etc.).
Suppose a photographer has a flash device with a guide number of 44 (m) / 144 (ft),[note 5] sets the camera's aperture to f/4, and wants to know the required flash-to-subject distance; he merely divides the guide number by 4. Thus, a subject 11 meters or 36 feet away will be correctly illuminated (GN 44 (m) f/4 = 11 m, and GN 144 (ft) f/4 = 36 ft). For the same guide number and an aperture of f/8, the light source must be 5.5 meters or 18 feet from the subject.
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