About the 1/250 x-sync flash rumor...

dlacouture · 10-18-2010, 06:49 AM

Falconeye, I've thought about how you made the high-speed video, and I'm curious about what orientation you used on the casio (IIRC, that's what you used, no?)...

I'd bet you used the casio in landscape orientation, but with the rolling shutter effect, would it not have been better to use it "sideways"?

The K7 shutter would take a sloping aspect, but maybe you could derive more precise measurements from the rolling shutter effect than just by the frames...
Granted, you'd have to know the speed of the rolling shutter to be able to conclude anything.

**Lowell Goudge** · 10-18-2010, 06:50 AM

Originally posted by falconeye

Every topic ends up mentioning FF, doesn't it?

the reason every 1/250 discussion ends with FF discussions is because the PZ-1 had 1/250 sync and was full frame.

My idea if pentax were to ever ever go FF would be to start with a PZ1 body, and put a sensor in it.

This would also give the old timers the aperture coupling as well.

But it'll never happen

falconeye · 10-18-2010, 06:59 AM

Originally posted by dlacouture

Falconeye, I've thought about how you made the high-speed video, and I'm curious about what orientation you used on the casio (IIRC, that's what you used, no?)...

I'd bet you used the casio in landscape orientation, but with the rolling shutter effect, would it not have been better to use it "sideways"?

Exilim is Casio, yes. Well, a frame is a frame and after 1ms it's over. And the motion blur should stay the same too as I guess each pixel is kept open for about 1ms.

You're right if I would have tried to measure the height of moving subjects in the video which I didn't

Christopher M.W.T · 10-18-2010, 07:35 AM

I don't get it, what would be so hard in implementing an electronic shutter?

junyo · 10-18-2010, 09:07 AM

Originally posted by Blue

No Pentax film body had shake reduction so what is your point?
I know the sizes of sensor and film so I don't need to see that 4 year or older diagram. The question I had asked Falk had to do with whether or not the shutter was big enough for a ff sensor.

For the record, the *istD was originally built for a ff sensor. The *istD, however predates SR. I don't if the current shutter is large enough for ff or not without SR or with SR, which is why I asked Falk.

The point is, the shutter aperture for a full 35mm frame is more than enough to handle a APSC sensor and it's range of movement for SR. It's a non-complicated problem. For the cost of a slight bigger shutter mechanism that you already know how to build you should be able to get a faster sync speed.

Bobe416 · 10-20-2010, 11:49 AM

I can understand why some people would want to use 1/250 of a second with their flash, but since the K-5 now allows ISO 80 (which is approximately 1/2 of a stop of less light from ISO 100) does this not mitigate the need to go from 1/180 to 1/250 shutter?

Blue · 10-20-2010, 01:39 PM

Originally posted by junyo

The point is, the shutter aperture for a full 35mm frame is more than enough to handle a APSC sensor and it's range of movement for SR. It's a non-complicated problem. For the cost of a slight bigger shutter mechanism that you already know how to build you should be able to get a faster sync speed.

You are assuming Pentax and other makers make their shutters. Pentax has historically relied on Seiko for there metal vertical run shutters. Pentax bodies that could sync at 1/250 had a top speed of 1/8000. Until the K-7 and K-5, no dSLR had a shutter that fast. Even the newer generation MZ-s and MZ-3 film cameras had only 1/6000 and 1/4000 top shutter speeds respectively. I can only guess like some have already done that in the last 10 years has concentrated on reliability and accuracy. The shutter in the PZ1p could probably average 150,000 actuation with +/1 a quarter stop. The Shutter in the K20d could likely go 300,000 actuations with closer tolerances. With the K-7 having a 1/8000 top speed, I suspected that firmware could up the 1/180 to 1/250 but that suspicion has never panned out. I guess we will have to see how it plays out on the K-5. I don't know who makes the shutters used in the K200d, K20d, K-7, K-5, K-x, and K-r.

dlacouture · 10-20-2010, 03:37 PM

Originally posted by Bobe416

I can understand why some people would want to use 1/250 of a second with their flash, but since the K-5 now allows ISO 80 (which is approximately 1/2 of a stop of less light from ISO 100) does this not mitigate the need to go from 1/180 to 1/250 shutter?

Well, you'd be losing flash power by lowering the iso... Same as using a ND filter.
Whereas going from 1/180 to 1/250 only has an effect on the ambient...

**Digitalis** · 10-20-2010, 04:03 PM

Originally posted by Christopher M.W.T

I don't get it, what would be so hard in implementing an electronic shutter?

This has been discussed before, and due to degradation of image quality electronic shutters will remain unusable for cameras with larger sensors.

falconeye · 10-20-2010, 04:29 PM

Originally posted by Bobe416

ISO 80 [...] does this not mitigate the need to go from 1/180 to 1/250 shutter?

As said, no.

But a stronger flash does mitigate this need. So, that Pentax AF540 has a GN of 54/m and Nikon SB900 has a GN of 62/m (Nikon GN of 34/m recomputed from 35mm to 50mm) means that in order to support the same ambient/flash ratio than Nikon at 1/250X, Pentax would need 1/290X.

On the other side, this ís all rather abstract. In real life, one would work with professional strobes and use as much light as required to obtain the required effect. So, it wouldn't matter because the strobes would always be strong enough. And of course, HSS flashes provide a low cost alternative.

mattdm · 10-20-2010, 05:02 PM

Originally posted by falconeye

So, that Pentax AF540 has a GN of 54/m and Nikon SB900 has a GN of 62/m (Nikon GN of 34/m recomputed from 35mm to 50mm)

Wait, what? The Pentax AF540FGZ has a GN of 54m with an 85mm lens on a full frame camera, or 57mm on the Pentax 1.5× APS-C dSLRs. The Nikon SB900 has a GN of 47mm at that same focal length. (Standard illumination pattern.)

Something must be lost in translation here.

falconeye · 10-20-2010, 05:43 PM

Originally posted by mattdm

Wait, what? The Pentax AF540FGZ has a GN of 54m with an 85mm lens on a full frame camera, or 57mm on the Pentax 1.5× APS-C dSLRs. The Nikon SB900 has a GN of 47mm at that same focal length. (Standard illumination pattern.)

Something must be lost in translation here.

We may both have wrong and correct pieces here. Let me try to sort it out. I am clearly wrong in some aspects!

These are my "fact" starting points:

1. AF540FGZ: http://www.pentax.jp/english/support/man-pdf/acc_st_af540fgz.pdf
GN (ISO100) at 85mm is 54m, at 50mm is 45m and at 35mm is 39m. I don't have the 540 but I thought that GN, if not specified otherwise, applies to 50mm and ISO 100. The Pentax web site specifies no focal length. An illegal spec IMHO. My fault anyway

2. SB900: SB-900 AF Speedlight from Nikon
GN (ISO100) at 35mm is 34m.

(The GN of 48 is SQRT(2)*34 and applies to ISO200). I was wrong in assuming that the GN would increase from 35mm to 50mm by the sterian angle difference (it increases less as is visible in the Pentax spec).

So, we have (35mm ISO 100 GN -- both not 50mm but I cannot find those):

AF540FGZ: GN 39m vs. SB900: GN 34m.

So, the Pentax flash is stronger and to match Nikon's 1/250X, Pentax needs 1/218X. Much more friendly looking numbers

Nevertheless, the GN are difficult to compare because of the zoom flash feature. E.g., the SB900 supports a very narrow beam which the AF540 doesn't, ie., the SB900 is stronger beyond 85mm.

mattdm · 10-21-2010, 06:23 AM

Originally posted by falconeye

1. AF540FGZ: http://www.pentax.jp/english/support/man-pdf/acc_st_af540fgz.pdf
GN (ISO100) at 85mm is 54m, at 50mm is 45m and at 35mm is 39m. I don't have the 540 but I thought that GN, if not specified otherwise, applies to 50mm and ISO 100. The Pentax web site specifies no focal length. An illegal spec IMHO. My fault anyway

In general, if not specified, they mean the most impressive number they can find -- usually the most-focused beam. Honestly, I'm surprised no one has started giving numbers at ISO 3200 instead of ISO 100.

You can find the full table for the Nikon flash in the SB900 user manual if you're really curious. The Nikon manual is far better in technical detail than the Pentax one. (It's as good or better than Metz.)

Originally posted by falconeye

So, we have (35mm ISO 100 GN -- both not 50mm but I cannot find those):

AF540FGZ: GN 39m vs. SB900: GN 34m.

At 50mm (full frame), it's

AF540FGZ: GN 45m vs. SB900: GN 40m.

Originally posted by falconeye

So, the Pentax flash is stronger and to match Nikon's 1/250X, Pentax needs 1/218X. Much more friendly looking numbers

Or 1/222X at 50mm.

Manufacturers in Japan, by the way, must give guide numbers within +/- 1 EV. I'm not sure how strictly this is enforced, but I think we can expect that degree of error for any given number. (Probably exaggerated on the high side, but one never knows without actual measuring.)

Originally posted by falconeye

Nevertheless, the GN are difficult to compare because of the zoom flash feature. E.g., the SB900 supports a very narrow beam which the AF540 doesn't, ie., the SB900 is stronger beyond 85mm.

Which is, of course, only 57mm on APS-C. This is one of the reasons Pentax needs to update their flash lineup.

falconeye · 10-21-2010, 07:59 AM

Originally posted by mattdm

You can find the full table for the Nikon flash in the SB900 user manual if you're really curious.

Matt, thanks for the update. Great to have your expertise on board

Looked into the SB900 manual.

Interesting how the Nikon GN at 50mm is only 40m. When it should be 62 (as I wrongly assumed) based on the sterian angle illuminated.

It is even worse for more narrow beams. The Nikon GN increases to 47m at 85m and only reaches the Pentax GN (54m) as late as at 180mm. At 200mm, it is 56m.

Imagine a proper zoom optics in front of the flash. E.g., what if we glue a matte screen into the filmholder plate of a film body, mount a 300mm f/4 and flash from behind the matte screen? Shouldn't that boost the 30mm GN by a factor 100, i.e., to about 3000? One could flash very distant subjects. Gives great new opportunities

(and like a ring flash, avoids the shadow) Maybe, a market niche for a tele flash?

Anyway, I find the current flash'es GN at tele zoom positions rather disappointing, I must say.

Blue · 10-21-2010, 08:23 AM

Originally posted by falconeye

. . .
Imagine a proper zoom optics in front of the flash. E.g., what if we glue a matte screen into the filmholder plate of a film body, mount a 300mm f/4 and flash from behind the matte screen? Shouldn't that boost the 30mm GN by a factor 100, i.e., to about 3000? One could flash very distant subjects. Gives great new opportunities

(and like a ring flash, avoids the shadow) Maybe, a market niche for a tele flash?

Anyway, I find the current flash'es GN at tele zoom positions rather disappointing, I must say.

'Super Beamer' . . .

10-20-2010, 05:43 PM	#42
falconeye Veteran Member Join Date: Jan 2008 Location: Munich, Alps, Germany Photos: Gallery Posts: 6,871	Originally posted by mattdm Wait, what? The Pentax AF540FGZ has a GN of 54m with an 85mm lens on a full frame camera, or 57mm on the Pentax 1.5× APS-C dSLRs. The Nikon SB900 has a GN of 47mm at that same focal length. (Standard illumination pattern.) Something must be lost in translation here. We may both have wrong and correct pieces here. Let me try to sort it out. I am clearly wrong in some aspects! These are my "fact" starting points: 1. AF540FGZ: http://www.pentax.jp/english/support/man-pdf/acc_st_af540fgz.pdf GN (ISO100) at 85mm is 54m, at 50mm is 45m and at 35mm is 39m. I don't have the 540 but I thought that GN, if not specified otherwise, applies to 50mm and ISO 100. The Pentax web site specifies no focal length. An illegal spec IMHO. My fault anyway 2. SB900: SB-900 AF Speedlight from Nikon GN (ISO100) at 35mm is 34m. (The GN of 48 is SQRT(2)34 and applies to ISO200). I was wrong in assuming that the GN would increase from 35mm to 50mm by the sterian angle difference (it increases less as is visible in the Pentax spec). So, we have (35mm ISO 100 GN -- both not 50mm but I cannot find those): AF540FGZ: GN 39m vs. SB900: GN 34m.* So, the Pentax flash is stronger and to match Nikon's 1/250X, Pentax needs 1/218X. Much more friendly looking numbers Nevertheless, the GN are difficult to compare because of the zoom flash feature. E.g., the SB900 supports a very narrow beam which the AF540 doesn't, ie., the SB900 is stronger beyond 85mm. Last edited by falconeye; 10-20-2010 at 05:48 PM.

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10-18-2010, 06:49 AM	#31
dlacouture Veteran Member Join Date: Jul 2008 Location: Var, South of France Photos: Albums Posts: 1,074 Original Poster	Falconeye, I've thought about how you made the high-speed video, and I'm curious about what orientation you used on the casio (IIRC, that's what you used, no?)... I'd bet you used the casio in landscape orientation, but with the rolling shutter effect, would it not have been better to use it "sideways"? The K7 shutter would take a sloping aspect, but maybe you could derive more precise measurements from the rolling shutter effect than just by the frames... Granted, you'd have to know the speed of the rolling shutter to be able to conclude anything.

10-18-2010, 06:50 AM	#32
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,888	Originally posted by falconeye Every topic ends up mentioning FF, doesn't it? the reason every 1/250 discussion ends with FF discussions is because the PZ-1 had 1/250 sync and was full frame. My idea if pentax were to ever ever go FF would be to start with a PZ1 body, and put a sensor in it. This would also give the old timers the aperture coupling as well. But it'll never happen

10-18-2010, 06:59 AM	#33
falconeye Veteran Member Join Date: Jan 2008 Location: Munich, Alps, Germany Photos: Gallery Posts: 6,871	Originally posted by dlacouture Falconeye, I've thought about how you made the high-speed video, and I'm curious about what orientation you used on the casio (IIRC, that's what you used, no?)... I'd bet you used the casio in landscape orientation, but with the rolling shutter effect, would it not have been better to use it "sideways"? Exilim is Casio, yes. Well, a frame is a frame and after 1ms it's over. And the motion blur should stay the same too as I guess each pixel is kept open for about 1ms. You're right if I would have tried to measure the height of moving subjects in the video which I didn't

10-18-2010, 07:35 AM	#34
Christopher M.W.T Veteran Member Join Date: Jun 2009 Posts: 1,689	I don't get it, what would be so hard in implementing an electronic shutter?

10-18-2010, 09:07 AM	#35
junyo Veteran Member Join Date: Oct 2007 Photos: Gallery Posts: 418	Originally posted by Blue No Pentax film body had shake reduction so what is your point? I know the sizes of sensor and film so I don't need to see that 4 year or older diagram. The question I had asked Falk had to do with whether or not the shutter was big enough for a ff sensor. For the record, the istD was originally built for a ff sensor. The istD, however predates SR. I don't if the current shutter is large enough for ff or not without SR or with SR, which is why I asked Falk. The point is, the shutter aperture for a full 35mm frame is more than enough to handle a APSC sensor and it's range of movement for SR. It's a non-complicated problem. For the cost of a slight bigger shutter mechanism that you already know how to build you should be able to get a faster sync speed.

10-20-2010, 11:49 AM	#36
Bobe416 Forum Member Join Date: Mar 2009 Location: Toronto Photos: Gallery \| Albums Posts: 57	I can understand why some people would want to use 1/250 of a second with their flash, but since the K-5 now allows ISO 80 (which is approximately 1/2 of a stop of less light from ISO 100) does this not mitigate the need to go from 1/180 to 1/250 shutter?

10-20-2010, 01:39 PM	#37
Blue Moderator Site Supporter Join Date: Jun 2008 Location: Florida Hill Country Photos: Gallery \| Albums Posts: 17,377	Originally posted by junyo The point is, the shutter aperture for a full 35mm frame is more than enough to handle a APSC sensor and it's range of movement for SR. It's a non-complicated problem. For the cost of a slight bigger shutter mechanism that you already know how to build you should be able to get a faster sync speed. You are assuming Pentax and other makers make their shutters. Pentax has historically relied on Seiko for there metal vertical run shutters. Pentax bodies that could sync at 1/250 had a top speed of 1/8000. Until the K-7 and K-5, no dSLR had a shutter that fast. Even the newer generation MZ-s and MZ-3 film cameras had only 1/6000 and 1/4000 top shutter speeds respectively. I can only guess like some have already done that in the last 10 years has concentrated on reliability and accuracy. The shutter in the PZ1p could probably average 150,000 actuation with +/1 a quarter stop. The Shutter in the K20d could likely go 300,000 actuations with closer tolerances. With the K-7 having a 1/8000 top speed, I suspected that firmware could up the 1/180 to 1/250 but that suspicion has never panned out. I guess we will have to see how it plays out on the K-5. I don't know who makes the shutters used in the K200d, K20d, K-7, K-5, K-x, and K-r.

10-20-2010, 03:37 PM	#38
dlacouture Veteran Member Join Date: Jul 2008 Location: Var, South of France Photos: Albums Posts: 1,074 Original Poster	Originally posted by Bobe416 I can understand why some people would want to use 1/250 of a second with their flash, but since the K-5 now allows ISO 80 (which is approximately 1/2 of a stop of less light from ISO 100) does this not mitigate the need to go from 1/180 to 1/250 shutter? Well, you'd be losing flash power by lowering the iso... Same as using a ND filter. Whereas going from 1/180 to 1/250 only has an effect on the ambient...

10-20-2010, 04:03 PM	#39
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by Christopher M.W.T I don't get it, what would be so hard in implementing an electronic shutter? This has been discussed before, and due to degradation of image quality electronic shutters will remain unusable for cameras with larger sensors.

10-20-2010, 04:29 PM	#40
falconeye Veteran Member Join Date: Jan 2008 Location: Munich, Alps, Germany Photos: Gallery Posts: 6,871	Originally posted by Bobe416 ISO 80 [...] does this not mitigate the need to go from 1/180 to 1/250 shutter? As said, no. But a stronger flash does mitigate this need. So, that Pentax AF540 has a GN of 54/m and Nikon SB900 has a GN of 62/m (Nikon GN of 34/m recomputed from 35mm to 50mm) means that in order to support the same ambient/flash ratio than Nikon at 1/250X, Pentax would need 1/290X. On the other side, this ís all rather abstract. In real life, one would work with professional strobes and use as much light as required to obtain the required effect. So, it wouldn't matter because the strobes would always be strong enough. And of course, HSS flashes provide a low cost alternative.

10-20-2010, 05:02 PM	#41
mattdm Veteran Member Join Date: Feb 2007 Location: Boston, MA Photos: Gallery Posts: 2,948	Originally posted by falconeye So, that Pentax AF540 has a GN of 54/m and Nikon SB900 has a GN of 62/m (Nikon GN of 34/m recomputed from 35mm to 50mm) Wait, what? The Pentax AF540FGZ has a GN of 54m with an 85mm lens on a full frame camera, or 57mm on the Pentax 1.5× APS-C dSLRs. The Nikon SB900 has a GN of 47mm at that same focal length. (Standard illumination pattern.) Something must be lost in translation here.

10-21-2010, 06:23 AM	#43
mattdm Veteran Member Join Date: Feb 2007 Location: Boston, MA Photos: Gallery Posts: 2,948	Originally posted by falconeye 1. AF540FGZ: http://www.pentax.jp/english/support/man-pdf/acc_st_af540fgz.pdf GN (ISO100) at 85mm is 54m, at 50mm is 45m and at 35mm is 39m. I don't have the 540 but I thought that GN, if not specified otherwise, applies to 50mm and ISO 100. The Pentax web site specifies no focal length. An illegal spec IMHO. My fault anyway In general, if not specified, they mean the most impressive number they can find -- usually the most-focused beam. Honestly, I'm surprised no one has started giving numbers at ISO 3200 instead of ISO 100. You can find the full table for the Nikon flash in the SB900 user manual if you're really curious. The Nikon manual is far better in technical detail than the Pentax one. (It's as good or better than Metz.) Originally posted by falconeye So, we have (35mm ISO 100 GN -- both not 50mm but I cannot find those): AF540FGZ: GN 39m vs. SB900: GN 34m. At 50mm (full frame), it's AF540FGZ: GN 45m vs. SB900: GN 40m. Originally posted by falconeye So, the Pentax flash is stronger and to match Nikon's 1/250X, Pentax needs 1/218X. Much more friendly looking numbers Or 1/222X at 50mm. Manufacturers in Japan, by the way, must give guide numbers within +/- 1 EV. I'm not sure how strictly this is enforced, but I think we can expect that degree of error for any given number. (Probably exaggerated on the high side, but one never knows without actual measuring.) Originally posted by falconeye Nevertheless, the GN are difficult to compare because of the zoom flash feature. E.g., the SB900 supports a very narrow beam which the AF540 doesn't, ie., the SB900 is stronger beyond 85mm. Which is, of course, only 57mm on APS-C. This is one of the reasons Pentax needs to update their flash lineup.

10-21-2010, 07:59 AM	#44
falconeye Veteran Member Join Date: Jan 2008 Location: Munich, Alps, Germany Photos: Gallery Posts: 6,871	Originally posted by mattdm You can find the full table for the Nikon flash in the SB900 user manual if you're really curious. Matt, thanks for the update. Great to have your expertise on board Looked into the SB900 manual. Interesting how the Nikon GN at 50mm is only 40m. When it should be 62 (as I wrongly assumed) based on the sterian angle illuminated. It is even worse for more narrow beams. The Nikon GN increases to 47m at 85m and only reaches the Pentax GN (54m) as late as at 180mm. At 200mm, it is 56m. Imagine a proper zoom optics in front of the flash. E.g., what if we glue a matte screen into the filmholder plate of a film body, mount a 300mm f/4 and flash from behind the matte screen? Shouldn't that boost the 30mm GN by a factor 100, i.e., to about 3000? One could flash very distant subjects. Gives great new opportunities (and like a ring flash, avoids the shadow) Maybe, a market niche for a tele flash? Anyway, I find the current flash'es GN at tele zoom positions rather disappointing, I must say.

10-21-2010, 08:23 AM	#45
Blue Moderator Site Supporter Join Date: Jun 2008 Location: Florida Hill Country Photos: Gallery \| Albums Posts: 17,377	Originally posted by falconeye . . . Imagine a proper zoom optics in front of the flash. E.g., what if we glue a matte screen into the filmholder plate of a film body, mount a 300mm f/4 and flash from behind the matte screen? Shouldn't that boost the 30mm GN by a factor 100, i.e., to about 3000? One could flash very distant subjects. Gives great new opportunities (and like a ring flash, avoids the shadow) Maybe, a market niche for a tele flash? Anyway, I find the current flash'es GN at tele zoom positions rather disappointing, I must say. 'Super Beamer' . . .