1/180th - please help me understand!

Hi,

Hoping for some advice. I've kind of come through the ranks with digital cameras, a simple point and shoot, then a Canon Powershot that really helped me learn the fundamentals then the K30 I have now.

I've never trusted flashes, mainly because I only ever had built in ones and the results were always very ... point and shoot-y.

But now I've, through this forum, decided to get an external flash that can help me, mostly inside, when the light's so marginal that it requires ISO that's just, in my opinion, too high.

It'll be mainly used to photograph my daughter, who is young, and moves around a lot. Quickly.

So what I want / need to know, is, what's this 1/180 thing all about? Why, in P-TTL mode, can't I set a quicker exposure? Surely the whole point of a flash is to do the things that wouldn't be possible with unaided light levels?

I'm not sure if, say at a party in a hall full of kids running around, 1/180 will be quick enough to avoid motion blur - so I guess I'm going to have to go to the high speed sync option.

I seem to have no choice in this - but is that what high speed sync is really for?

Sorry for the long post, but a few words of advice, just to get me going in the right direction, would be much appreciated.

Where possible I'd like to use as much ambient light as possible, the idea being I just point the flash at the ceiling or a wall, and just give what light there is a bit of a helping hand.

---

K30; DA35 2.4; DA50 1.8; A35-105 3.5; Sigma 70-300 F4-5.6 APO DL; M 80-200 F4; 18-55 WR Kit; Sigma 24-70 2.8

The 1/180 sync speed is a limitation of the way a focal plane shutter works, one curtain opens and the other follows it leaving a strip travelling over the sensor. The faster the shutter speed the narrower that strip, the sensor at shutter speeds shorter than 1/180 would only have a narrow strip exposed by the flash because the flash duration is incredibly brief. At shutter speeds of 1/180 or longer the sensor is fully exposed before the second curtain moves.

With flash the effective exposure for Time isn't actually the camera's shutter speed but in fact the duration of the flash which could be in the region of 1/20000 second. So you won't have any problems with freezing motion.

---

Ken
“We must avoid however, snapping away, shooting quickly and without thought, overloading ourselves with unnecessary images that clutter our memory and diminish the clarity of the whole.” - Henri Cartier-Bresson -

As Ken has said, for the main flashlit subject the extremely brief flash burst will freeze movement assuming the subject is in range - but backgrounds may still be blurred though depending on the shutter speed and if there's any camera movement during the exposure.

So the main purpose for 'high speed sync' is therefore not so much to freeze movement , but rather to allow the use of flash for creative and 'fill' purposes in bright conditions (ie when the ambiant light is high enough that 180th sec would cause overexposure).

The common scenario is an outdoor portrait where a bit of shadow needs to be lifted on the face, but there's bright light all around. You might want a wide aperture (say f3.5) for a nice portrait rendering, but even at ISO 100 this may give a speed of, say, 1000th sec in daylight. Without HSS you can't use the flash at that speed. With a flashgun set to HSS the gun fires a very rapid continuous burst of flashes that lasts for the whole time the shutter is open (1000th sec in our case here).

This is actually not 'fast' at all in flash terms - in fact very slow. But it allows the shutter speed to be correct for the ambiant light and means the flash stays on for the whole duration of the exposure (while the curtain strip is exposed). HSS actually uses more power than most single flash bursts as is it illuminating for so much longer, and the practical effect of this is that the maximum disance you can use it at is reduced (for any given ISO / Aperture), and the batteries will be used up a little more quickly if you use it a lot.

---

My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver

With the K-30 on Tv or M exposure mode, and an AF360FGZ or AF540FGZ flash set to High Speed Synch, you can use flash at any shutter speed you choose, even up to the fastest 1/6000th/sec.

The 1/180th limit is the fastest shutter speed you can use with a single flash of light because any faster, and the trailing curtain has already started to obscure the sensor before the leading curtain has reached the end of it's travel.

Put simply, at speeds faster than 1/180th, less than 100% of the sensor area is exposed at the same time, which is what you need for a single flash of light.

---

Peter E Smith

My flickr Photostream

Thanks for that - so - just point and click!

I suspect that in the environments I intend to use it - where there is usually already artificial light - the 'spoil' of the ambient light isn't as harsh as in natural light, because artificial light is much uglier than natural light anyway.

So thank you - I think the message is 'trust 1/180 because it's not, in these circumstances, as slow as you think'.

Flash photography is going to be an interesting journey for me - I've already been surprised by the quality of some 'flash assisted' images I've taken around the house today - and obviously the actual technical image quality is so much higher at lower ISO.

Thanks again.

---

K30; DA35 2.4; DA50 1.8; A35-105 3.5; Sigma 70-300 F4-5.6 APO DL; M 80-200 F4; 18-55 WR Kit; Sigma 24-70 2.8

ears, sometimes 'point & shoot' will work for flash, but often not, or not very well at least. Any camera systems maximum flash sync speed (eg 180th sec) is going to be limiting in certain situations, such as those brighly lit portraits I was talking about where you need 'fill' light on the subject, so moving to a dedicated flashgun that offers the High Seed Sync mode is the way to go.

Keep your eyes out on the forum as I'm just about to start a new thread on flash modes and flash exposure systems on Pentax, with a view to members contributing their knowledge & experience to build a guide and knowledge base on these matters .... fun fun to come !

---

My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver

Already done http://www.mattmatic.co.uk/pentax-dslr-flash-guide-available.

---

Peter E Smith

My flickr Photostream

Thanks McGreg - I will. Perhaps I should have been clearer, sorry, I've just obtained a Mecablitz 50 from the forum so have a little room for learning and manouvre.

I've played with the settings and worked out how to use P-TTL, and also the HSS mode, but just wanted to make sure I wasn't doing anything silly - I'm taking photos at a big occasion tomorrow and, as I've never really done it before, wanted to make sure I don't make any silly mistakes.

Will mainly be photographing kids, playing and moving around a lot, in a large hall that will probably be tungsten lit.

I've never used anything other than full manual mode on the camera and I'm pretty used to that now so don't mind messing around with settings.

---

K30; DA35 2.4; DA50 1.8; A35-105 3.5; Sigma 70-300 F4-5.6 APO DL; M 80-200 F4; 18-55 WR Kit; Sigma 24-70 2.8

Done and dusted as it turns out - link broken.

---

K30; DA35 2.4; DA50 1.8; A35-105 3.5; Sigma 70-300 F4-5.6 APO DL; M 80-200 F4; 18-55 WR Kit; Sigma 24-70 2.8

I added the fullstop, sorry.

http://www.mattmatic.co.uk/pentax-dslr-flash-guide-available
http://www.mattmatic.co.uk/otheritems.html

---

Peter E Smith

My flickr Photostream

It's a very complete and well written guide to modern Pentax flash systems, well worth the small cost.

Matt is a mod here but doesn't post as regularly as he once did in the good 'ole days .

---

Peter E Smith

My flickr Photostream

I have found that in party situations pentax cameras and pentax flasguns set to P give terrific results with a pleasing balance between ambient and fill in flash particularly if you are bouncing the flash off the ceiling and extending the catchlight panel

---

Ken
“We must avoid however, snapping away, shooting quickly and without thought, overloading ourselves with unnecessary images that clutter our memory and diminish the clarity of the whole.” - Henri Cartier-Bresson -

Thanks Ken. Sorry to hijack my own thread with what's probably a simple question - but what is program mode? I've looked in the manual but it's not clear - 'sets exposure according to the program line' is about the best I can wring out of it. Not prone to over-elaboration in those manuals are they?

I get sensitivity priority, aperture, exposure priorities, auto, bulb but that seems to cover all the bases - in program mode, what preference do I set, and what does the camera do for me?

Sorry!

---

K30; DA35 2.4; DA50 1.8; A35-105 3.5; Sigma 70-300 F4-5.6 APO DL; M 80-200 F4; 18-55 WR Kit; Sigma 24-70 2.8

T
Of course we've got that which is great, but that doesn't mean there's nothing else to say ... Its always good to keep refreshing ideas, and we've had a update to the range lately with the af II series ... They have lost the sensor on the flash unit itself, so no longer allowing auto-flash operation with non-da lenses, quite a significant change if you're looking fir a new flashgun.

And all the more important then to talk about the most efficient manual working techniques. Its never done and dusted, that sort if thinking just stifles learning and developing ... There's always scope for new ways of approaching things ... I can assure you that any material I create will take a new perspective and will complement, not duplicate that which we already have

---

My Guides to the Pentax Digital Camera Flash Lighting System : Download here from the PentaxForums Homepage Article .... link
Pentax K7 with BG-4 Grip / Samyang 14mm f2.8 ED AS IF UMC / DA18-55mm f3.5-5.6 AL WR / SMC A28mm f2.8 / D FA 28-105mm / SMC F35-70 f3.5-4.5 / SMC A50mm f1.7 / Tamron AF70-300mm f4-5.6 Di LD macro / SMC M75-150mm f4.0 / Tamron Adaptall (CT-135) 135mm f2.8 / Asahi Takumar-A 2X tele-converter / Pentax AF-540FGZ (I & II) Flashes / Cactus RF60/X Flashes & V6/V6II Transceiver

I for one are looking forward to your guide - thank you.