Please help, my brain is pickled !

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testbloke

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Kevin
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Now that I am just starting to make sense of my camera and understand exposure and composition, I am ready to confuse myself some more and look into an off camera flash.
I have entry level DSLR, a Pentax K-m with only the two kit lenses, so cannot justify spending hundreds of pounds.
My obvious starting point was the Pentax manual recommended flashes, google pricing as such :-
AFS540FGZ £287 - A bit too pricey for me
AFS360FGZ £174
AF200FG £91

£91 would be ideal but I could stretch to the 360 if the difference was worth it, but have read that the 360 in auto mode underexposes one stop. Generally I am looking to add some fill flash / get better flash qaulity for "candid portrait" shots of my daughter. Depending on the results from this, I may look to try some more formal studio shots. I currently try to avoid flash totally as the on camera flash is very harsh.
I am also very keen on the smoke art and water droplets tutorials on the forum and probably, at least at first, this would be the primary use.

I am baffled as to the tech on the flashes, and what it actually means (TTL etc). I am also confused if the Pentax or an independant (sigma / jessops / vivitar) would be best and more cost effective, the range of flashes available seems even more bemusing than cameras and lenses !

One last thing, will the external flash allow a faster shutter than the current 1/180 sec ?

Sorry if this is going over old ground but I would appreciate anyone who takes the time to reply.
 
testbloke said:
I am baffled as to the tech on the flashes, and what it actually means (TTL etc).
Click to expand...

TTL means through the lens. The camera measures the actual light coming through the lens when the shutter is open and switches it off when enough light has been received.

testbloke said:
One last thing, will the external flash allow a faster shutter than the current 1/180 sec ?
Click to expand...

A focal plane shutter has two curtains. When you press the shutter release, the first curtain opens. After a suitable time (dependant on the shutter setting, the second curtain closes shutting off the light.

For slow shutter speeds this is an open - wait - close routine.

At higher speeds the second shutter starts to close before the first curtain has finished opening. This supplies the film or sensor with a travelling slit of light. The faster the speed, the narrower the slit.

If you use a shutter speed faster than your sync. speed (in this case 1/180). The flash will fire after the second curtain has started to close so some of the image will be masked by the shutter.


Steve
 
Steve, thanks for explenation, so even with off camera flash I will be limited to 1/180 as this is the cameras limitation.
I take it TTL is a desirable feature then for ease of use (ie for a novice like me).
 
A focal plane shutter has two curtains. When you press the shutter release, the first curtain opens. After a suitable time (dependant on the shutter setting, the second curtain closes shutting off the light.

For slow shutter speeds this is an open - wait - close routine.

At higher speeds the second shutter starts to close before the first curtain has finished opening. This supplies the film or sensor with a travelling slit of light. The faster the speed, the narrower the slit.

If you use a shutter speed faster than your sync. speed (in this case 1/180). The flash will fire after the second curtain has started to close so some of the image will be masked by the shutter.
Click to expand...
That has got to be the best explanation ever.
 
"If you use a shutter speed faster than your sync. speed (in this case 1/180)."

Sorry, having just re-read this, is this the sync speed of the camera or the flash, ie if my external flash can sync at 1/500, does this mean a faster shutter speed can be used
 
testbloke said:
"If you use a shutter speed faster than your sync. speed (in this case 1/180)."

Sorry, having just re-read this, is this the sync speed of the camera or the flash, ie if my external flash can sync at 1/500, does this mean a faster shutter speed can be used
Click to expand...
As Steve explained, the limiting factor is your camera (actually your shutter) because the shutter has to be fully open at the time the flash is fired.

So, your flashgun can theoretically work regardless of the shutter speed and would work at 1/500th if your camera shutter was fully open at that speed - but it isn't so it can't.
 
Okay, cheers, now got it ! (At last they say !).

One more stupid question if I may ...
Is there then a "best of both world" option, a flash that can be set off camera as a light to bring the ambient lux up so I could shoot my water droplets without flash then use faster shutter speed ?

I think I know the answer but just in case, I am just trying to get the best from my limited funds.
 
testbloke said:
"If you use a shutter speed faster than your sync. speed (in this case 1/180)."

Sorry, having just re-read this, is this the sync speed of the camera or the flash, ie if my external flash can sync at 1/500, does this mean a faster shutter speed can be used
Click to expand...

Yes, it does mean you can sync at 1/500sec, if you have a flash gun such as those listed in the OP, that has high speed sync capability and will sync at any shutter speed.

If you think about how focal plane shutters work, as explained by Steve above, then you can see why normal flash which has a very short duration of 1/1000sec and usually much less, can only sync up to a maximum speed - 1/180sec in the case of your Pentax K-m; hence Garry's reply.

But if your flash has high speed sync capability, what it does is pulse the flash tube rapidly over a much longer duration, effectively becoming continuous light for a long enough time to allow the focal plane shutter to complete its full routine and sync at any shutter speed.

This is a function of the flash gun, not the camera. It works great for fill flash in bright sun for example, but it really gives the flash a major workout and maximum range is substantially reduced. It also increases recycle times and eats batteries, but when you want it or need it, it's a real life saver. Great feature found on most good guns these days :)
 
testbloke said:
Okay, cheers, now got it ! (At last they say !).

One more stupid question if I may ...
Is there then a "best of both world" option, a flash that can be set off camera as a light to bring the ambient lux up so I could shoot my water droplets without flash then use faster shutter speed ?

I think I know the answer but just in case, I am just trying to get the best from my limited funds.
Click to expand...

Yes, you could do that with the high speed flash function of a dedicated flash like those you have listed on your OP, but I'm not sure why you would want to.

You can get much shorter exposure times with flash by switching to manual power and turning it down. Every time you half the power output, you halve the flash duration (roughly) so when you get down to 1/32 power output, your flash duration is going to be around 1/30,000 sec.
 
Garry Edwards said:
That has got to be the best explanation ever.
Click to expand...

Well.... possibly in the top ten!

There is another type of shutter which most of my film cameras have. This is an in-lens shutter and works in a similar way to the aperture iris (except that it closes all the way).

These shutters usually run up to 1/500 and will sync. with a flash at any speed.


Steve.
 
HoppyUK, you are a star and also answered another question (what is HSS).
Therefore if I get a flash with HSS capability, I can use it as fill flash for portraits, then if doing water drop shots (for example), I can use the HSS feature to increase the shutter speed beyond the 1/180 sec if required but use with leaniancy as it gives the flash a workout. By workout, do you mean the flash units have limited life, or just the batteries get eaten ?
 
I don't know much about this high speed sync. stuff but would I be correct to assume it spreads the flash out over a time at around 1/125?

In that case, the sum of all the pulses must be equal to the power of a single flash in one burst as there is just the on capacitor charging up.

Therefore, if you use a shutter speed of 1/500 then you are only getting a quarter of the power.

Or can you adjust the flash to suit the shutter speed you are using?


Steve.
 
testbloke said:
HoppyUK, you are a star and also answered another question (what is HSS).
Therefore if I get a flash with HSS capability, I can use it as fill flash for portraits, then if doing water drop shots (for example), I can use the HSS feature to increase the shutter speed beyond the 1/180 sec if required but use with leaniancy as it gives the flash a workout. By workout, do you mean the flash units have limited life, or just the batteries get eaten ?
Click to expand...

Yes, you've got it :)

Don't worry about over working the flash, it won't wear out. But if you cane it with a rapid sequence of full power shots it will struggle to keep up and will overheat and cut out for a few minutes if you really over cook, but unlikely in most situations. It's most useful when you want to use flash but need a higher shutter speed than 1/180sec to balance with the ambient light, ie fill flash in bright sun.

You could use this facility with a very high shutter speed to freeze water droplets, but I think it would be easier to switch to manual and just use the very short flash durations you get when you turn the power down. You can usually overcome any potential difficulties with ambient light, if there are any, by juggling f/number and ISO.
 
Steve Smith said:
I don't know much about this high speed sync. stuff but would I be correct to assume it spreads the flash out over a time at around 1/125?

In that case, the sum of all the pulses must be equal to the power of a single flash in one burst as there is just the on capacitor charging up.

Therefore, if you use a shutter speed of 1/500 then you are only getting a quarter of the power.

Or can you adjust the flash to suit the shutter speed you are using?


Steve.
Click to expand...

I think that's right Steve, and as a result range is cut substantially. Same effect as using one of your FP bulbs, or maybe a long line of flash powder ;)

The flash strobes incredibly quickly at around 40Khz, and I think the tube glows continuously, as well as effectively continuously. I don't know what the total burn time is but your guess of 1/125sec is sounds about right.

As far as I know this is fixed, which makes sense because the total function time of a focal plane shutter is pretty much the same at all of the highest speeds. Certainly there is no facility to change it on my Canon 580EX but it wouldn't surprise me if it does indeed vary if it can sense the camera model it's attached to and knows the total shutter function time. If it does actually do that, it could be made slightly more efficient at highest shutter speeds, and a lot more efficient when coupled to to high x-sync speed cameras that can run up to 1/250sec. Every ms counts when you're pushing it.
 
Okay, you are confusing me again. I think I am on the wrong track with the HSS, as mentioned (if I understand correctly) I can reduce the flash power to increase the shutter speed. At the end of the day, this is compensating for my poor timing, rather than getting the perfect timing for the water drop, I could fire more frames and have more chance of catching !
Mainly, I am looking for some fill flash on this kind of pic :-

and getting the flash off to the side (between object and background) when doing the smoke art and water drop type shots so I dont have to spend hours in photoshop removeing cast shadows and glare from the built in flash.
 
testbloke said:
Okay, you are confusing me again. I think I am on the wrong track with the HSS, as mentioned (if I understand correctly) I can reduce the flash power to increase the shutter speed. At the end of the day, this is compensating for my poor timing, rather than getting the perfect timing for the water drop, I could fire more frames and have more chance of catching !
Mainly, I am looking for some fill flash on this kind of pic :-
3830111028_cf47a4d462.jpg

and getting the flash off to the side (between object and background) when doing the smoke art and water drop type shots so I dont have to spend hours in photoshop removeing cast shadows and glare from the built in flash.
Click to expand...

I don't think you have quite got it ;)

You don't reduce the flash power to increase the shutter speed - the shutter speed remains the same with flash, as that's how focal plane shutters work. The flash duration effectively becomes your shutter speed, and reducing power reduces flash duration. (We must be careful with terminology here as it can get confusing - shorter and longer are less ambiguous.)

If you want to photograph droplets, freezing it is no problem. There are vaious way you could do it, but I would get the flash close so that not only do you get a very short duration (either on TTL auto or manual) but the flash will recycle very quickly (which it almost certainly won't in high speed mode). Then set the camera on continuous, x-sync 1/180sec, and rattle off a few frames. You will be surprised how hard it is to time it precisiely, and you might be better firing it manually, but keep trying and you'll get it right eventually.

Phew! :D

For your beach shot, high speed flash is perfect for fill in although in this pic you hardly need it. If you set the camera up correctly (probably on aperture priority) it will balance the ambient and flash exposures for you on auto TTL. Really useful when it's bright, or when you want to use a low f/number to throw the background out of focus which would normally give you an impossibly high shutter speed for flash to be possible. It's a great feature for that :thumbs:

All I would say there is that getting the flash ratio right is often down to personal taste and if the flash is too strong it looks artificial. Take a quick snap and chimp it on the LCD, then if the flash is too bright turn it down a bit, or if the background is too dark, make the shutter speed longer. Or vice versa - it's really easy. You'll get nice bright faces and a lovely sparkle in the eyes :)
 
Sooooo ...

Would I then be better just getting a wee (cheap) flash for some fill on the shot like the beach shot above (and to place off camera between the smoke and the background for the smoke art and similar shots) and get a couple of lamps etc for a mini studio in the house ?
 
testbloke said:
Sooooo ...

Would I then be better just getting a wee (cheap) flash for some fill on the shot like the beach shot above (and to place off camera between the smoke and the background for the smoke art and similar shots) and get a couple of lamps etc for a mini studio in the house ?
Click to expand...

Nooooo...

For fill flash on the beach, you need the high speed flash sync feature. You won't get that with a cheap gun.

For your other projects, you will almost certainly need to be able to adjust power manually, and this is not a feature of cheap guns.

If you get one of the dedicated Pentax guns, you will get all this, plus the brilliant TTL auto flash system. You sound like a Scotsman :D
 
HoppyUK said:
You sound like a Scotsman :D
Click to expand...

LOL, cheeky monkey. Cant spend money I dont have. Should have got into this 3 years ago when our income was double and had no kids !
Ah well, mortgage holiday and decent flash it is then !
Maybe i can get some work round at Gary's cleaning his baackdrop or something :)

PS - having just checked ebay and got an old 50mm prime for under a tenner, you could be right - true scotsman !
(ebay item 300339288719). Scarey manual lens !
 
Some food for thought,

I have this flash

AFS540FGZ

But I hardly use it, I've had it over 12 months, and it's been on the camera twice, three times at most. My most used flash are the 2 vivitar 285's that I use off camera, and they're dirt cheap.

Only advantage it gives me is rear curtain sync which I can't get off camera (and if Pentax don't sort that soon, along with a full frame body, I'll be switching to C or N)
 
JasonRS said:
Some food for thought,

I have this flash

AFS540FGZ

But I hardly use it, I've had it over 12 months, and it's been on the camera twice, three times at most. My most used flash are the 2 vivitar 285's that I use off camera, and they're dirt cheap.

Only advantage it gives me is rear curtain sync which I can't get off camera (and if Pentax don't sort that soon, along with a full frame body, I'll be switching to C or N)
Click to expand...

Thanks for advice, I have seen the vivitar mentioned before, I am struggling to compare specs to see what I would be losing and how this relates to the effect on the pictures.
I am now thinking that I might be best getting a vivitar / cheaper unit, when I use it I will then learn how to use it and what features woul dbe nice, then if necessary and funds allow, I can upgrade to a better unit later.
Alternatively, you could sell me your 540 :naughty:

I am finding this a hard call, purchasing the camera was much easier !
 
If you're planning on using the flash on the camera, get the 540 (not sellling mine, it has it's uses!) or the 360 (less power though) Everything's automatic if you want it to be.


If you're going the way of off camera flash, the cheaper ones are fine, but you'll need to do some manual work in adjusting power etc.

If you're unsure as to whether you will go the route of off camera flash, buy the 360/540, and buy the most power you can afford!
 
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