[violaferenc]

Hello helpers!

I've got a pair of studio reflectors that I connect via " PC + top shoe converter HSA-PSU" to my Pentax K70. When I want to shoot for example shutter speed 200 or higher with any aperture value, the reflectors don't flash.
Also, I made a photo with shutter 0'4/f 11. When I tried to change the shutter speed, the images were almost the same! Speed was 0'4, then 6, then 50, than 160 (this is the fastest that works with relfectors). I made 6 almost the same images with each having a totally different shutter speed and the same aperture?
Does anyone have a clue what is going on here? I sometomes use old Canon EOS1D. With it, I can use any shutter speed with no problem.
Thanks in advance...

[Arvid]

The camera can't shoot with a higher shutter speed than 1/160, that's the fastest shutter speed at which the whole frame area is fully exposed (this can vary by model and maker, Pentax seems to be on the low side here) and thus allows for the flash light to hit the whole sensor area at once. At higher speeds, the second shutter curtain closes before the first one traveled the whole distance. If you'd use a higher shutter speed, the duration of the flash is too short to hit all areas of the sensor and you'd see a black bar on the frame. To avoid this, the camera simply doesn't allow any higher shutter speed when using flash.

Lower speeds are generally no problem, because the shutter will stay fully open for some amount of time, when you use them. If ambient light is so low that the sensor doesn't register much or anything, it doesn't matter if the shutter stays open for 2 seconds or 1/160 of a second - the amount of light from the flash is responsible for the exposure then. That could explain why all exposures seem to look the same. If there's enough ambient light available, you should be able to notice some effects of overexposure (most likely motion blur, which a tripod would rule out). Unless your camera is set up to compensate for this automatically (highlight correction, for example? Don't know about the avaiable features on the K70 and how you set it up).

I am no expert on flash photography, but this maybe will give some hints about stuff to look into.

[jatrax]

I sometomes use old Canon EOS1D. With it, I can use any shutter speed with no problem.

This is not likely, the Canon 1D has a sync speed of 1/500, much higher than the K-70 but it is still limited to that speed. Try your 1D at 1/1000 and see if it works there.

As @Arvid explained the strobes will not fire if the shutter speed is higher than the sync speed. On the K-70 that is 1/160. His explanation of why you are not seeing a difference in exposure with different shutter speeds is also most likely correct. However, another possibility is that you some auto function, such as auto ISO, turned on and the camera is adjusting make the exposure correct regardless of the shutter speed.

[stevebrot]

I've got a pair of studio reflectors that I connect via " PC + top shoe converter HSA-PSU" to my Pentax K70. When I want to shoot for example shutter speed 200 or higher with any aperture value, the reflectors don't flash.

As noted above, your K-70 will not provide sync above 1/180s* unless the hot shoe device communicates to the camera that it supports High Speed Sync (HSS) through the Pentax P-TTL protocol. As a result, doing HSS with your camera requires appropriate P-TTL capable flash or speedlight setups capable of P-TTL emulation at the hot-shoe interface. Studio strobe HSS support is quite another thing, though I believe there are at least two vendors (Priolight and Cononmark) that provide P-TTL HSS products ($$$).


Steve

* This or similar restrictions on X-sync speed are part of using flash with a focal plane shutter. The historic design approach has been to simply let the user learn from experience by capturing the shadow of the trailing curtain resulting in a wasted shot for speeds over the sync speed. Pentax has opted to not allow the user the value of experience by not providing sync in any mode at shutter speeds higher than the sync speed. The only exception is when a HSS-capable flash is detected with a body supporting HSS.

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Last edited by stevebrot; 01-17-2018 at 11:39 AM.

[clackers]

Hello helpers!

I've got a pair of studio reflectors that I connect via " PC + top shoe converter HSA-PSU" to my Pentax K70. When I want to shoot for example shutter speed 200 or higher with any aperture value, the reflectors don't flash.

Hi VF,

Like on Canon, you need equipment to support High Speed Sync.

Also, I made a photo with shutter 0'4/f 11. When I tried to change the shutter speed, the images were almost the same! Speed was 0'4, then 6, then 50, than 160 (this is the fastest that works with relfectors). I made 6 almost the same images with each having a totally different shutter speed and the same aperture?

The pictures all look the same in a studio because shutter exposure is irrelevant to the flash.

I do see people try to brighten a picture by halving the shutter speed instead of increasing ISO or aperture, and think, 'WTF? We're not outdoors."

[violaferenc]

Wow guys!Thanks a lot!
I appreciate the thoroughness you showed in your answers. I understand the first part of the answers - 160 is the limit. However, the second part is still vague...
So do you think I can purchase certain equipment and achieve for example shooting with strobes at 250 speed? Or the K70 limit is final?
Also I don't get it: If I can shoot at daylight at 1000 speed, why can't I in manual mode do the same in "studio"? And to the camera it should be all the same if there's lens cap on or there's Supernova in front of it - is the light from the strobes so late or early that the K70 doesn't catch it?
Thanks guys, you're great help.

[Wheatfield]

This is not likely, the Canon 1D has a sync speed of 1/500, much higher than the K-70 but it is still limited to that speed. Try your 1D at 1/1000 and see if it works there.

As @Arvid explained the strobes will not fire if the shutter speed is higher than the sync speed. On the K-70 that is 1/160. His explanation of why you are not seeing a difference in exposure with different shutter speeds is also most likely correct. However, another possibility is that you some auto function, such as auto ISO, turned on and the camera is adjusting make the exposure correct regardless of the shutter speed.

The flash is controlling the amount of light hitting the sensor, not the shutter. It doesn't matter much what shutter speed he shoots with flash presuming the amount of light in the studio is dim and he is stopping down a bit.

[amoringello]

Wow guys!Thanks a lot!
I appreciate the thoroughness you showed in your answers. I understand the first part of the answers - 160 is the limit. However, the second part is still vague...
So do you think I can purchase certain equipment and achieve for example shooting with strobes at 250 speed? Or the K70 limit is final?
Also I don't get it: If I can shoot at daylight at 1000 speed, why can't I in manual mode do the same in "studio"? And to the camera it should be all the same if there's lens cap on or there's Supernova in front of it - is the light from the strobes so late or early that the K70 doesn't catch it?
Thanks guys, you're great help.

If you're in the studio, can you explain why you feel that you need a faster shutter speed??
You should be able to control the studio environment such that flash is the controlling factor in freezing any action.

Pentax disables flash above the x-sync speed. Unlike other brands which allow what's been called "hypersync" which allows flash with faster shutter speeds -- with limited success, depending how much you can accept those limitations. :-)
Best you can do is use P-TTl compatible flashes that allow HSS. You can use Pentax brand flashes, Cactus has an option, as do some more recent brand options that range $1000-$2000 per head.
If you're shooting outdoors and need faster shutter speed, you're looking at a lot of $$$ to out-power the sun. (HSS reduces flash power, so you'll need to use multiple flashes in many cases with the lower cost options.)

[jatrax]

The flash is controlling the amount of light hitting the sensor, not the shutter. It doesn't matter much what shutter speed he shoots with flash presuming the amount of light in the studio is dim and he is stopping down a bit.

I know.

[clackers]

Wow guys!Thanks a lot!
I appreciate the thoroughness you showed in your answers. I understand the first part of the answers - 160 is the limit. However, the second part is still vague...
So do you think I can purchase certain equipment and achieve for example shooting with strobes at 250 speed? Or the K70 limit is final?

Yes. HSS equipment like the Pentax 360 and 540 speedlights do this, no problem.

Also I don't get it: If I can shoot at daylight at 1000 speed, why can't I in manual mode do the same in "studio"? And to the camera it should be all the same if there's lens cap on or there's Supernova in front of it - is the light from the strobes so late or early that the K70 doesn't catch it?
.

Not just your K70 but your friends' Canons, Nikons and Sonys are the same.

HSS is used so that the flash can evenly light the frame as the shutter with its two curtains opens and closes in front of the sensor.

In a studio where you've stopped down so the ambient is zero you can freeze motion like liquid drops or breaking glass with a shutter time of ten seconds, because the only light is coming from the flash, and its duration might only be 1/10000s.

[Wheatfield]

I know.

It doesn't sound like the OP did.

[sterretje]

Also I don't get it: If I can shoot at daylight at 1000 speed, why can't I in manual mode do the same in "studio"? And to the camera it should be all the same if there's lens cap on or there's Supernova in front of it - is the light from the strobes so late or early that the K70 doesn't catch it?
Thanks guys, you're great help.

See the part in reply #2 about the curtain(s).

[violaferenc]

If you're in the studio, can you explain why you feel that you need a faster shutter speed??
You should be able to control the studio environment such that flash is the controlling factor in freezing any action.

Pentax disables flash above the x-sync speed. Unlike other brands which allow what's been called "hypersync" which allows flash with faster shutter speeds -- with limited success, depending how much you can accept those limitations. :-)
Best you can do is use P-TTl compatible flashes that allow HSS. You can use Pentax brand flashes, Cactus has an option, as do some more recent brand options that range $1000-$2000 per head.
If you're shooting outdoors and need faster shutter speed, you're looking at a lot of $$$ to out-power the sun. (HSS reduces flash power, so you'll need to use multiple flashes in many cases with the lower cost options.)

I am beginner at using flashes and strobes. I was trying to take photo of parfume bottle with the black background. With 0,4/f11 the bottle was perfect, but the background was grey. I wanted to increase the shutter speed in order to get darker background, something like low key photo. And then it happened - several photos with different shutter speed , all pretty much the same.

[amoringello]

I am beginner at using flashes and strobes. I was trying to take photo of parfume bottle with the black background. With 0,4/f11 the bottle was perfect, but the background was grey. I wanted to increase the shutter speed in order to get darker background, something like low key photo. And then it happened - several photos with different shutter speed , all pretty much the same.

ah! That makes things so much clearer. :-)
Yes, shutter speed will affect *ambient* light. Shutter will not affect most *flash* light, because flash is often faster than your possible shutter speed.

For motionless objects in a studio, this is a more straight forward task (although not necessarily easy) since you should have near complete control of your environment.
You are likely using enough (too much?) flash that the background is also being flood-lit by your flash.
You need to find a way to prevent your flash from lighting the background.

Many potential solutions, you need to figure out what will work. Just couple of options....
1) Move the background further away (look up "Inverse Square Law" with regard to light getting dark faster as you move away from the source.)
2) "Flag" or block off the light from the flash so it does not shine on the background.
3) Use some light modifier (soft box, grid, etc...) to limit where the light falls
4) Change the angle of the flash to keep the light from shining on the background

also, think of putting up black walls around your studio area to prevent flash from bouncing off walls, cabinets, or anything else in the room.

This might result in needing the flash being placed very close to your object (barely out of frame) at a lower power, and your background being a few feet away.
This in turn may result in your needing more lights to properly light all angles of your object.... and you're collection of lighting equipment grows, and grows and grows..... :-)

[violaferenc]

ah! That makes things so much clearer. :-)
Yes, shutter speed will affect *ambient* light. Shutter will not affect most *flash* light, because flash is often faster than your possible shutter speed.

For motionless objects in a studio, this is a more straight forward task (although not necessarily easy) since you should have near complete control of your environment.
You are likely using enough (too much?) flash that the background is also being flood-lit by your flash.
You need to find a way to prevent your flash from lighting the background.

Many potential solutions, you need to figure out what will work. Just couple of options....
1) Move the background further away (look up "Inverse Square Law" with regard to light getting dark faster as you move away from the source.)
2) "Flag" or block off the light from the flash so it does not shine on the background.
3) Use some light modifier (soft box, grid, etc...) to limit where the light falls
4) Change the angle of the flash to keep the light from shining on the background

also, think of putting up black walls around your studio area to prevent flash from bouncing off walls, cabinets, or anything else in the room.

This might result in needing the flash being placed very close to your object (barely out of frame) at a lower power, and your background being a few feet away.
This in turn may result in your needing more lights to properly light all angles of your object.... and you're collection of lighting equipment grows, and grows and grows..... :-)

Wow! Thanks! I actualy know about all this you have listed, however I didn't remember to use it. I just started to experiment with those things. Thanks for the memo list, I'll try to keep it in mind at all times.