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03-17-2009, 04:20 AM   #1
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Non-TTL / Auto Flash compatibility w/ istDS

Hi, I just recently got a used Pentax *ist DS, and I have a question about the flash (normal one non-ttl) compatibility with ist DS. I've read the manual and search google to no avail.

My previous camera was Panasonic FZ50. Being a low budget amateur, i found that the Panasonic's dedicated flashes too expensive. So, to make story short, i eventually got a used Nikon SB-20, it's the cheapest i could get with the features i wanted (auto with 5 aperture settings, manual with 5 power ratio, can be tilted, etc)

Of course, the TTL of Nikon and Panasonic arent matched, so I removed 3 of the pin/contacts and leaving just the middle pin (pictures can be seen here). This way, my SB-20 is just a normal flash, non-TTL AFAIK. Anyway, it works flawlessly on FZ50, on auto and manual mode.

I've also checked the voltage, it's 2-3v so it should be safe both on FZ50 and *istDS. But when i mount the flash on my DS, my DS doesnt recognize the flash at all. At first i thought the pins are dirty but i've cleaned them up and it's still the same. So I've a few questions about this:

1. Can istDS work with normal/non-TTL/auto flash like my 'special' SB-20?
2. On FZ50, when the flash is mounted and turned on, I can see the external flash icon on FZ50 lcd. Is there any similar icon in Pentax istDS top LCD, back LCD or viewfinder?
3. I notice that the pins on my DS have the exact same location with the pins on my SB-20, so, if the answer of no. 1 is a no, would it wise to try putting back the pins on SB-20 (I still keep them) and try mounting on DS again?

Thanks in advance.

03-17-2009, 06:23 AM   #2
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For the camera to recognize that it has a flash on it, the flash has to have compatible communication circuitry, and compatible communication pins. You are putting a flash that has neither onto your camera, and if you put the pins back onto your flash you still have a flash that most likely won't have compatible communication circuitry.
However, the flash should still work as an autoflash, providing it works at all.
03-17-2009, 06:37 AM   #3
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Thank you for answering. That's what i'm trying to achieve, to use the SB-20 as an auto flash. I can live with auto / non-ttl flash. But apparently it doesn't work. Although it works with FZ50. FZ50 uses panasonic's TTL, but it also recognize my SB-20 as an auto flash. I want to confirm whether Pentax istDS actually does not recognize auto flash at all, or my istDS has some defect the previous owner escaped to tell me.
03-19-2009, 12:49 PM   #4
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Auto flash on *istDS

An autoflash doesn't need to be "recognized" by the camera, since the camera can't control it.

I have a K10D, not an *istDS, but the operation should be the same. Set your camera in manual mode. Set the shutter speed to the highest x-sync speed. On my K10D, that is 1/180 second. Check your manual for the highest speed on your camera. You can use a slower speed if you like. In some situations, this is very useful.

The manual for the SB-20 should have a chart telling you what aperture to use for various ISO values. There may be a mini-chart or dial calculator on the flash itself. Set the aperture for that value.

Shoot.

With an autoflash, the aperture remains constant. The flash senses when enough light has bounced back from the subject and quenches the flash early, if necessary. For this reason, the flash duration varies, typically from 1/1000 second down to 1/30,000 or even 1/50,000. The closer the subject, the shorter the flash duration.

The max sync speed is the fastest shutter speed at which the entire sensor is exposed at one time. A focal plane shutter is actually two shutters, a leading (opening) and trailing (closing) shutter. When the shutter is tripped, the leading curtain opens. At some later point (the shutter speed setting), the closing curtain closes. At speeds above the sync speed, the closing curtain begins closing before the opening curtain is fully open, resulting in a slit moving across the sensor. The faster the shutter, the narrower the slit. At speeds at or below the sync speed, the opening shutter is fully open before the trailing shutter begins closing, thus exposing the entire sensor.

If your camera does not fire the flash at all, make sure that the shutter speed is at or below the max sync speed. I don't believe that my K10D will fire the flash when the shutter speed is above 1/180. However, my flash is a Pentax-dedicated autoflash (Promaster 5500, with autoflash module), so my camera knows when the flash is mounted and charged. It won't even LET me set the shutter speed faster than 1/180.

When using an auto or fully manual flash, it is pointless to try to use any camera mode other than manual. The flash duration takes the place of shutter speed (unless you want to "drag" the shutter) and the aperture is determined solely by the power of the flash.

03-19-2009, 02:46 PM   #5
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If there is an X setting on the mode dial, try it.

Paul
03-19-2009, 03:33 PM   #6
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DS shouldn't have problem wiht auto flash. As long as camera recognizes there is a flash in the hot shoe it should set Tv automaticaly and fire off the flash when shutter pressed. You need to care about matching ISO and Av setting of the camera and flash.
Is the hot shoe on your DS working?
03-19-2009, 03:48 PM   #7
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Not sure what sort of "recognition" you're hoping for. It is likely that a Pentax-branded/dedicated auto flash might serve some small purpose like indicate flash-ready in the viewfinder, and possibly force the shutter speed to X-sync (1/180 on your DS)...but this probably isn't necessary for basic operation.

For what it's worth, there are lots of inexpensive used TTL flashes available for Pentax as well, and they'll work on *ist D/DS/DS2...they're inexpensive in part because they aren't really supported by the newer Pentax D-SLRs.
03-20-2009, 09:58 AM   #8
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The auto-Thyristor control of many flashes works nicely and (in my experience) even better, than Pentax (P)-TTL on the digital bodies.

If you use a flash with the simple center contact, the camera will NOT recognize, that you have added a flash. So you need to make the necessary adjustments manually: set the camera to sync-shutter speed or something longer in M (manual) mode). Dial in the aperture of the lens you use on the flash and the correct ISO setting. Do not use anything like Tv (shutter speed priority) ot auto-ISO on the camera - that is important.

With this settings the flash should work reliably.

Some flash guns make better use of the communication pins. For example more modern Metz flash guns (though most won't support P-TTL), will read the ISO and aperture setting of the camera and set the auto-Thyristor control accordingly. They can force the camera to set the sync-speed, but that is not necessary. That's convenient and basically the same as P-TTL, without the pre-flash.

Ben

03-20-2009, 04:49 PM   #9
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@noblepa: Thanks I'll try M mode and 1/180 (or slower) shutter speed, right now I dont have the flash with me but will in 1 or 2hours.

@Paul Hunt: Nope, there's no such on thing on DS's dial, but thanks anyway!

@axl: Yes, that was my expectation, but something's definitely wrong.. Could be the DS hotshoe, that's why I'm asking if there is any icon somewhere on DS which confirms whether DS recognizes mounted flash on its hotshoe or not, something that Panasonic FZ50 does..

@AndrewG NY: The recognition I'm hoping for is just a sort of icon or something on DS body that tells me it recognized the flash, or not. You said, with Pentax-dedicated flash there's a flash ready icon visible in viewfinder? How about non-dedicated flash, can anyone confirm this? Thank you.

Ben_Edict:I agree, I think for my limited need auto-flash is sufficient. Now I just have to make it work! I'll try cleaning the hotshoe contact again and set the sync shutter speed and M mode, thanks.
03-20-2009, 05:05 PM   #10
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I have a Pentax 540, but I use a Nikon SB-25 (with the data pins removed, just like yours. Here it is.) and a Vivitar 283 a lot. Mine is a K10D, but I don't think it's different from the *ist DS as far as non-dedicated flash is concerned.

I also use the SB-25 and the 283 with my Canon G5 the same way I use them with the K10D.

- Pentax cameras, any of them, have no way to recognize/acknowledge a non-dedicated flash. I'm surprised that the FZ50 has this feature.

- So you have to set the camera to M mode, shutter speed at max sync speed (it's 1/180 sec for the K10D) or slower. ISO and aperture settings should match the settings on the flash.

- Do not put the data pins of the SB-20 back.

Use the SB-20 on the *ist DS, just as you did with the FZ50. It works fine.
03-20-2009, 05:06 PM   #11
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The flash will work fine, but there is no way for the camera to recognize it. This is not a big deal at all. Set your shutter speed to the flash sync speed or slower. Set your ISO to your preferred setting. 4x ISO will double the range of the flash at a given f/stop. Set the flash to an aperture that will give you the range you need using the scales on the back of the flash. Set your camera to the f/stop indicated by the scales.

The scales actually do nothing to the flash output - they just tell you what will happen at a given ISO and give f/stop.

The one caution I will add to the information here is that a zoom lens with a variable aperture will require a different f/stop at different zoom levels. If your aperture is 4 at the widest angle and 5.6 at the longest, then you need to interpolate the f/stop you use to take this into account. It is often good enough to set the camera to the aperture mid way along the range.
03-20-2009, 05:06 PM   #12
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I don't think there is icon. On K100/10 there isn't icon. You know camera recognizes the flash when you have it in Av and the exposure time is locked to certain value no matter what f stop, ISO or light situation...
BR
03-20-2009, 05:16 PM   #13
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QuoteOriginally posted by axl Quote
I don't think there is icon. On K100/10 there isn't icon. You know camera recognizes the flash when you have it in Av and the exposure time is locked to certain value no matter what f stop, ISO or light situation...
BR
Oh, come on, axl. Don't feed the guy irrelevant information.

The flash in question is a NON-dedicated flash, plain and simple. The camera does not recognize it.

QuoteOriginally posted by Canada_Rockies Quote
The scales actually do nothing to the flash output - they just tell you what will happen at a given ISO and give f/stop.
In a sense, they do something in this case. There are 5 aperture settings on the SB-20. The scales change according to the aperture setting.
03-20-2009, 05:19 PM   #14
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QuoteOriginally posted by SOldBear Quote
In a sense, they do something in this case. There are 5 aperture settings on the SB-20. The scales change according to the aperture setting.
Yes, but that is the only thing that changes - the numbers on the scales. The scales on the flash do not affect the flash output.
03-20-2009, 05:20 PM   #15
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QuoteOriginally posted by SOldBear Quote
Oh, come on, axl. Don't feed the guy irrelevant information.

The flash in question is a NON-dedicated flash, plain and simple. The camera does not recognize it.
......
Sorry, I was under the impression that camera recognizes any flash in hot shoe.
but I might be wrong....
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