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05-18-2010, 10:51 AM   #1
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flashes

So i am polanning on getting a flash, but i don t know anything about flashes. can anyone tell me where i can find infomartion about flashes? i tired researching it and i only got the same info, get the strongest flash. which i agree but i want to know what the numbers mean, how to make ur flashes stonger or weaker ect... plz help
thank you!

05-18-2010, 01:18 PM   #2
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This thread and Matt's website should give you a general idea about the capabilities of the different types of currently available flash guns, that support the Pentax P-TTL flash control system:
https://www.pentaxforums.com/forums/camera-studio-accessories/43215-pentax-p-...omparison.html

For most flashes you will find the following basic numbers given:

GN = Guide Number = light output ("power") of the flash at a given ISO (sensor sensitivity, usually ISO 100, but some manufacturers cheat and use ISO 200, to make the number appear bigger) and at a given distance (either meters or feet).

The GN is of great practical value, to first anticipate the max. reach of the flash gun in any automatic mode and secondly, to calculate the correct aperture for a perfect exposure, when using a fully manual flash.

EXAMPLE: GN = 60 (metric). If you want to shoot an subject 5 meters away, just compute GN/distance = aperture, here 60/5 = 12 - This would be an extremely powerful flash and you would need to close down the aperture far (to f/12) to achieve a correct exposure at 5 meters distance.

GN = 30 (metric). Same shot, will give you 30/5 =6, which means an aperture setting of f/6 (or use the standard f-number of f/5.6).

This would be a fairly standard flash gun with a medium power.

What you see immediately:
– dividing the Guide Number through the shooting distance (use same measures for GN and distance, aka either feet or meters), will give you the required f-number
– doubling the the GN will allow you closing down the aperture two more f-stops
- halving the GN will force you to open the aperture by two more f-stops

THe Guide number is dependent on:
– real light output of the flash
- the setting of the flash reflector.

The flash reflector in older flash guns is usually a fixed thing and will illuminate the field of view of a 35mm lens on a 35mm film camera (roughly equivalent to using a 24mm lens on the Pentax DSLRs). If you use a wider lens, the wider field of view will not be fully illuminated, you get dark borders/corners.

Thus older flashes will give you a GN, which refers to a reflector with roughly 67 deg. illumination angle.

In newer flash guns, the reflector is often moveable and thus the illumination agnle will change, for instance, between 72 degs to 20 degs. What you recognize immediately: if the reflector is in its wide setting, the light will be distributed over a larger area and thus be less bright on each point . If the reflector is in its narrow setting, the illumination angle will be small and the brightness will increase. The manufacturers usually will not state the illumination angle, but refer to these angles as equivalent for lenses with a certain focal length. So you will find flash guns with reflector settings reaching from 28mm to 80mm or 24mm to 105mm, which are simply the focal lengthes they will optimally illuminate, when these lenses are used on a 35mm film camera.

That can be translated into Guide Numbers. Thus a flash gun with GN 30 at its widest setting may reach 45 at its longest setting. The GN varies with the illmuniation angle.

Cunning manufacturers nowadays state the GN for the longest setting and even well reputed manufacturers see the need to to so, too, because otherwise their flash guns will look less powerful.

So, when comparing Guide Numbers be careful and look, whether the numbers stated
– are given for the same ISO
– are given for a comparable illumination angle/reflector setting


Another parameter to look for in flash guns is the choice of operation modes:
– P-TTL = full flash control by the Pentax camera (equivalent to Canon E-TTL or Nikon iTTL)
– TTL = the older fully automatic flash control system for Pentax film cameras and only a handful of old Pentax DSRs - no current modell supports this old mode!
– "Auto" or Auto-thyristor mode. An automatic flash control mode, which the flash itself handles. Therfor it has a photo diode, which measures the flash output during the flash duration and stops the output, when there is enough light for the scene.
A very reliable mode with many flash guns and also available on many old flash guns of the pre-P-TTL era.
– "Manual" - the flash will fire off a "certain amount of light" without any control. YOu have to calculate the correct aperture setting from GN and distance (see above). SOme flash guns offer the possibilty to choose fractions of the full output, like 1/2, 1/4, 1/8 well down to 1/64 or even less. This can be important, if you shoot at very near distances or need to use a very wide aperture, when a higher output would lead to overexposure.

Shutter speed does not play any role for the exposure of the image, when using flash guns. It will only control the level of the ambient light. This is, because the flash duration is so short (between 1/600s and 1/30000s, the higher the output the longer and vice versa), that the flash must fire during the fully open shutter time. The shortest fully open shutter speed is usually the so-called (and as such on the program dial marked) x-synch time (1/180s for many Pentax cameras). Any shorter shutter speed will give you a black shadow in the image, as the shutter, while travelling over the image area will block the flash light somewhere. Longer expsoure times are fine, because at any time from the x-synch and longer, the shutter will completely free the image area for a long enough time to record the full flash with the sensor.

-- I know the shutter thing is very short and a bit confusing, but just have a look into the Wikipedia and you sure will find, how a shutter works and understand , why it can block the flash light at short shutter speeds).--

Anything else? Bevore buying and using an old flash gun, make sure, its trigger voltage is safe for the DSLR. Pentax gave for some cameras a limit of around 30volts, I prefer to stay below 12volts. You do not know, what the trigger voltage is: do a Search here and you'll find lots of threads with info.

If you have more specific questions now, keep on asking!

Ben
05-18-2010, 05:34 PM   #3
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:0... wow, thats alot of information. Thank you very very much!
i sort of get some of these things, but i think i will learn better if i actually have one in hand.
I have a k20d, i want to get a good flash ranging around 200, which one would be good? if their are better one at a higher price which on is it?
i saw on a pentax flash video that spoke about wireless capability, and i believe it was without hotshoes? is that the same with other off brands or in brands?
05-18-2010, 05:39 PM   #4
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ef-530 dg super < does that work with k20d? and isnt that a very powerfull yet good quality flash?

05-18-2010, 05:49 PM   #5
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QuoteOriginally posted by jolee1990 Quote
I have a k20d, i want to get a good flash ranging around 200, which one would be good?
This puts you at the mid range Pentax AF360FGZ, Metz 48 AF-1, or Sigma EF-530 DG Super.

QuoteOriginally posted by jolee1990 Quote
if their are better one at a higher price which on is it?
Pentax AF540FGZ or Metz 58 AF-1.

QuoteOriginally posted by jolee1990 Quote
i saw on a pentax flash video that spoke about wireless capability, and i believe it was without hotshoes? is that the same with other off brands or in brands?
With any of the five flashes listed above (and no others) you can do wireless P-TTL (automatic) flash controlled by the built-in flash on any current Pentax dSLR. The protocol is reverse-engineered by Metz and Sigma, so there are few little quirks (I had trouble with the K10D's low-light focus assist mechanism triggering the EF-530 DG Super accidentally that wouldn't be an issue with the K-7.)

QuoteOriginally posted by jolee1990 Quote
ef-530 dg super < does that work with k20d? and isnt that a very powerfull yet good quality flash?
Sure. Excellent value for the money. I find the controls quite awkward compared to the others, but many people really like it.
05-18-2010, 06:02 PM   #6
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Thank you very much Ben and Matt. If i have more questions ill ask
05-19-2010, 07:11 AM   #7
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QuoteOriginally posted by jolee1990 Quote
ef-530 dg super < does that work with k20d? and isnt that a very powerfull yet good quality flash?
I wanted a powerfull no frills flash so I went with the EF 530 DG and have not been disappointed.
05-19-2010, 07:13 AM   #8
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Metz 48AF1 is a great option for those on a budget ... a very capable piece of kit ...

05-19-2010, 09:01 AM   #9
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Basically, with flash, the FLASH exposure is solely determined by flash power (actually duration, how long the bulb is actually firing for), aperture and ISO. Ambient exposure is determined by ISO, shutter speed, and aperture (just like without any flash), so the trick is balancing the two. If I'm indoors in a smallish room (such as in someone's house), I usually just forget about ambient since the flash is powerful enough to light up the entire room (hence the 1/180s below, if the flash didn't fire, I'd have a more or less black picture) Now although you're shooting MANUAL Mode, that's only for the ambient exposure (the exposure needle in the viewfinder will blink warning you about underexposure, but ignore that). The camera's P-TTL metering will determine the needed flash output for a proper exposure.

Here's something I wrote on another forum -
"Easy" recipe for great P-TTL flash shots -
1)Point flash at ceiling/wall (to the side or behind you, experimentation is the key!)
2)Put camera in MANUAL mode on the mode dial
3)Set FEC to +1 on the flash head

4)Shoot RAW (this allows you to recover some highlights that might get blown as a result of #3 above)

5)Set ISO to 200 (to start)
6)Set shutter speed to 1/180s
7)Set f-stop to whatever DOF you want


Now if the flash runs out of "power" because of high ceilings, you can raise the ISO or open up the f-stop to compensate. Or you can slow down the shutter to bring more ambient light into the exposure (in addition to adjusting ISO/f-stop) If the ceiling is REALLY high (like in a church), you may need a reflector to throw some of the light forward (I use the Joe Demb Flip-it).

Quick and dirty outdoor fill flash tutorial -
Basically, if your subject is in shade and the background is bright (ie under a tree) or majorly backlit, fill flash is your friend. Think of those times when you got a properly exposed background, but the subject was almost pitch black.

Put camera into Av mode, metering will set the shutter speed to expose the overall shot (which in the situations that call for fill-flash will generally be the background) based on your selected aperture/ISO.
Make sure flash is set to HSS (in case your shutter speed go faster than 1/180s) and P-TTL. Fire away! The shutter speed/f-stop/ISO will expose the background, and the flash should output enough power to light up the foreground.

Now to control the background exposure, you use exposure compensation on the camera body (which would adjust the shutter speed), to adjust how much fill for the flash exposure, you use Flash exposure compensation. The trick is balancing the two (as it is with indoor work), and that comes with experience/experimentation.
05-19-2010, 09:03 AM   #10
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IF the flash is providing all the illumination (which it generally is in a small-ish room with you bouncing it off the ceiling), the shutter speed AND how dark it is do NOT matter AT ALL.

Try this - Pick a room in your house at night. Have a bunch of lights on. Set the shutter speed to 1/180s, aperture to f/5.6, ISO400. Point the flash straight up towards the ceiling (make sure the flash is in PTTL). Shoot.

Then turn off ALL THE LIGHTS, so it's pitch black. Do not change any settings. Take a picture. The picture should turn out the same, AND the flash wouldn't even have to work any harder. Basically, the flash is hitting the ceiling, and turning the ceiling into a large light source. THIS light source is providing all the illumination to the picture. How much flash power you need depends on the aperture, the ISO, and the distance from the light source to the subject. How dark the room is has NO affect on how much flash power is needed.

Now if you went with ISO400, 1/180s f/5.6, and did NOT turn the flash on, the shot should be pretty dark, even with the lights on.

Now turn the flash back on, but adjust the shutter speed to 1/100s. The shot will probably look VERY close to the first two shots (you can turn the room lights back on now ) Then try 1/50s, 1/25s....Eventually you'll see the room lights "creeping" into the picture. This leads into the next paragraph...

A "flash picture" is made up of TWO distinct exposures. The "ambient" exposure if comprised of shutter speed, ISO, and f/stop. The "flash" exposure is comprised of ISO, f/stop, and flash power (and of course the distance from the light source to the subject) In the above example, the ambient exposure is essentially nil, so the picture is completely made up by the flash "components".

Once you nail using the flash to provide ALL the illumination, you can move onto more advanced topics such as balancing flash and ambient exposures.
05-19-2010, 11:18 AM   #11
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wow egordon99 thank you!
i am going to try all these things that are being recommended once i get a flash.
one thing i wondered about flashes is, what does the numbers on the name of the flashes mean? such as, promaster 2500EDF or pentax af 540 fgz ? what do these 3500 and 540 mean? and what is the unit called when talking abouth the power of the flash? is it FEC as Egordon mentioned? is promaster af 7500df stronger than the Pentax AF540FGZ or Metz 58 AF-1. or the ef-530 dg super? i am trying to find the cheapest but strongest and advance flash (even though thats almost impossible) through even off brands.
05-19-2010, 11:23 AM   #12
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also, can those flashes that i mentioned above have swivel head ? and can i use it to bounce the flash off walls ectt? basicly do they have all the capabilities needed for an advance flash unit?
05-19-2010, 11:49 AM   #13
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QuoteOriginally posted by jolee1990 Quote
one thing i wondered about flashes is, what does the numbers on the name of the flashes mean? such as, promaster 2500EDF or pentax af 540 fgz ? what do these 3500 and 540 mean? and what is the unit called when talking abouth the power of the flash? is it FEC as Egordon mentioned? is promaster af 7500df stronger than the Pentax AF540FGZ or Metz 58 AF-1. or the ef-530 dg super? i am trying to find the cheapest but strongest and advance flash (even though thats almost impossible) through even off brands.
The numbers in the flash name are just names, marketing designations. Some are derived from the guide number, others not. They don't say anything.

Ben
05-19-2010, 12:02 PM   #14
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QuoteOriginally posted by jolee1990 Quote
wow egordon99 thank you!
i am going to try all these things that are being recommended once i get a flash.
one thing i wondered about flashes is, what does the numbers on the name of the flashes mean? such as, promaster 2500EDF or pentax af 540 fgz ? what do these 3500 and 540 mean? and what is the unit called when talking abouth the power of the flash? is it FEC as Egordon mentioned? is promaster af 7500df stronger than the Pentax AF540FGZ or Metz 58 AF-1. or the ef-530 dg super? i am trying to find the cheapest but strongest and advance flash (even though thats almost impossible) through even off brands.
The numbers are just a model number. Like An Audi A4...What's the "4" supposed to mean?
05-19-2010, 12:04 PM   #15
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QuoteOriginally posted by jolee1990 Quote
also, can those flashes that i mentioned above have swivel head ? and can i use it to bounce the flash off walls ectt? basicly do they have all the capabilities needed for an advance flash unit?
The 540 does swivel, and is probably your best bet. I had one when I shot Pentax and it was a nice unit. I've moved to the "dark side" and shoot with a Canon 580EXII and 430EXII, and the Pentax 540 was very comparable to the 580EXII (Canon's flagship flash)
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