Hacking a Pentax 4P grip for the AF540-FGZ


MattMatic

Link Posted 18/07/2007 - 12:57
You may have seen one of these:
http://www.bdimitrov.de/kmp/flashes/misc/grip.jpg

It's a 4P, old style grip for the Pentax systems. It's very compact, has a great detachable camera plate and space for 8 x AA batteries inside.

However, the hotshoe mount shorts out the extra pin on the AF540 and AF360 which makes the flash go a little AWOL. I had bodged a temporary solution by isolating the hotshoe with a piece of 35mm film ()

Last night I finished a little modification job on the grip and thought I'd share the information

As usual - absolutely no responsibility taken for you reading this and messing up your grip or flash. This information is just to stop frustration for those that attempt to do this.

Predrill
This step is to make the hole in the plastic for the locking pin.
I used a 1.5mm drill bit in a pillar drill to make a small hole that is in line with the left hand contact, and directly between the plastic and the metal of the hotshoe grip. (Make a measure with a piece of paper if it helps).
The drill will probably just mark the metal and make a hole in the plastic. You'll do the metal hole in the next steps...

Disassembly
1 ) Loosen the two silver screws on the mount joint (where the camera plate clicks in) and remove the silver band and clip from the grip. You'll need to also unscrew the AA battery cover (the big round cover at the bottom of the grip)

2 ) Remove the small black screw just in front of the hotshoe mount at the top.

3 ) Carefully peel back the texture from the rear half (the side with the red switch) and this will reveal three black screws. Remove these

4 ) Unclip and hinge out the front half of the grip.

5 ) Under the hotshoe you should see an earth tag - remove the small nut

6 ) Use a very well fitting jeweller screwdriver and carefully unscrew the four black screws in the hotshoe. DO NOT MANGLE the heads. Because the screws have been dabbed with a touch of glue/threadlock you have to be extremely careful - I had to scrape some of the green gunge off before unscrewing.

7 ) Having removed the hotshoe metal plate, you need to use a needle file to file out...

8 ) The corresponding hole in the metal for the locking pin

9 ) A large semicircle next to the front right screw hole. This ensures that the extra pin on the AF540 won't touch the hotshoe plate. I found it useful to slide the metal plate onto the bottom of the AF540 to see if I had the alignment right (taking into account the little bump of plastic that stops the flash from sliding right to the front of the metal).

10 ) While in there, I sliced off about one-quarter off the rubber pads that are in the AA battery bays. (The NiMH batteries I used wouldn't go in and let me screw the bottom plate on).

11 ) Reassembly was the reverse of the above - but fitting the metal plate back to the underside of the hotshoe was extremely fiddly


With that complete I can mount the AF540 onto the hotshoe, screw in the 5P cable into the side of the AF540 and connect to the camera.
Beautiful

(I have some images which I'll posted later...)

Hope that helps someone else fathom out what to do!
(And if you have a 4P grip and want the job done, and can pay by PayPal, I could probably find some time to modify it for you... if you ask nicely!)

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

Don

Link Posted 18/07/2007 - 13:03
cool idea.
I was thinking about drilling ahole in my off camera flash adapter...Gerri loves (for reasons I can't fathom) using flash brackets, and we've had one flash unit fall off when the flash wasn't properly locked....
Fired many shots. Didn't kill anything.

MattMatic

Link Posted 18/07/2007 - 13:24
Don,
I like this flash bracket. I've used the Metz 50MZ5 which is a real beast, but the grip is so huge it just feels uncomfortable. The Pentax one is just perfect. It is a heavy kit - K10D+grip, flash grip + AF540 with 8 extra AA batteries, but it just handles so well

And the fact that you can disconnect the camera bracket from the flash grip with a single push button (which can be locked, incidentally!) means that I can do a two-handed portrait mode - K10D+grip in right hand, and flash in the left hand. Really, really quick and useful

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

Don

Link Posted 18/07/2007 - 14:34
I know alot of people use'm but for me the ideal is simply a hip bag, and the short dedicated off camera flash cord kit. Holding the flash in one hand (with my index finger laying on the top of the flash (it's a natural ability for people to be able to point at something with thier index finger, without having to look at thier finger) aim the flash and shoot with the camera in the other hand...(often using the off camera flash with the on camera flash in contrast control mode.)
Fired many shots. Didn't kill anything.

amoringello

Link Posted 18/07/2007 - 14:51
Interesting device!
With the extra batteries, do you get faster recycle times? Or simply more flashes.

I was looking to get the TR-3? battery pack for the 540. But it appears the flash can be powered from the hotshoe?

As the 4-AAs inside the flash just bleed out too quickly, and the battery pack is pretty expensive, I would love to mod up a constant power supply or a hip pack connecting through the hotshoe.

What sort of voltage does that put out? i.e. Does that hotshoe grip convert the voltage first (like to the 300v for the power input on the side of the 540) or is it taking straight from the 8-AAs?

MattMatic

Link Posted 19/07/2007 - 09:21
Quote:
With the extra batteries, do you get faster recycle times? Or simply more flashes.

Just storage... and more weight.
They are not connected in any way.
Just did a 230 shot session yesterday with the bracket and a remote AF360 with brolley. Only the AF360 needed batteries replacing after about 190 shots - thought that was pretty excellent, IMHO.

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

gartmore

Link Posted 19/07/2007 - 13:48
Well I've been using the 4p grip for some time with a 240ft gun, 5p curly cable and adaptor (Fg I think, the one that looks like a hot shoe that fits onto a hotshoe but can only be used with the ring flash) on top of the ds. No problems at all, I thought 5p was 5p... or maybe not?

You can keep extension cables in the grip instead of batteries if you like.

Ken
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 -

MattMatic

Link Posted 19/07/2007 - 14:00
If the extra pin is shorted to ground then the zoom and P-TTL functions go completely AWOL. As I mentioned, it's a problem with the newer flashes that require digital communication to work at all (and stopping that communication isn't very helpful!).
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

amoringello

Link Posted 19/07/2007 - 14:05
Quote:
Only the AF360 needed batteries replacing after about 190 shots - thought that was pretty excellent, IMHO.

WOW! I usually end up replacing batteries after maybe 40 shots or less. I usually start running into recycle times of 10 seconds or more by then.

Is that perhaps an indication that I am doing something wrong in forcing the flash to use more battery power than necessary? Perhaps I just need to use higher ISO more often?

Don

Link Posted 19/07/2007 - 14:09
combination of wider apertures and faster iso= smaller discharges, faster recycle times, longer battery life and better balance of ambient and flash exposures.
Fired many shots. Didn't kill anything.

MattMatic

Link Posted 19/07/2007 - 14:14
Quote:
Is that perhaps an indication that I am doing something wrong in forcing the flash to use more battery power than necessary? Perhaps I just need to use higher ISO more often?

That's probably what it was... I was balancing the ISO against available light. So I was shooting at f/2.8 to f/5.6 (with the 50mm f/1.4 mostly) and varying the ISO between around 320 and 640.
It was kind of "instinctive" with the ISO adjustments I was making - after 3 test shots I had a pretty good feel for the flash+brolley setup, and as the shoot progressed worked out roughly what to do based on flash-to-subject distance.

Just have to love the K10D for the ease of ISO adjustment

I'm talking ambient lighting that would require ISO800 to ISO1600 - so the flash was within a couple of stops of ambient. That's probably why it just kept firing away (I didn't want that Deer-In-Headlights look )

EDIT: I also get used to listening out for the "thwack-zzzzzeeeeeurgh" sound of the flash fully discharging and recycling. When it hits that I know I've gone waaaay too far!

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

LiamD

Link Posted 19/07/2007 - 20:07
amoringello wrote:
Quote:
Only the AF360 needed batteries replacing after about 190 shots - thought that was pretty excellent, IMHO.

WOW! I usually end up replacing batteries after maybe 40 shots or less. I usually start running into recycle times of 10 seconds or more by then.


Hi,

do you use rechargeables? I use Uniross 2500mAh in my 360, and although I've probably only taken 70 or 80 shots, plus modelling light, with it, they're still going strong.

At about £1 a cell, and a fast charger for £10 (IIRC), they'll work out far cheaper in the long run. You're meant to get around 1000 charge cycles per cell before they go bad. I've got four sets, (and bought 4 battery cases for £2 to keep them in) as I use them for my DL as well (7-800 shots probably per charge), and I've never been caught out !!!!! famous last words.

HTH

Cheers

Liam
Liam


"Make your hands respond to what your mind demands." Jesse James

Best wide-angle lens? Two steps backward. Look for the 'ah-ha'. Ernst Haas

amoringello

Link Posted 19/07/2007 - 21:16
I normally use Duracell or Energizer. Usually the E2 or whatever they're pushing as their high output cells intended for cameras and whatnot.
(Regular alkaline are quite poor.)

I think, though, that I always shoot at ISO 100 in fear of getting noise. I think if I go to 400, I can get a bit more life.

Although I do have to say that the 2500mAh rechargeables really do a number for the istD. With the istD shelved as a backup, maybe I'll give those a try.

LiamD

Link Posted 19/07/2007 - 23:44
amoringello wrote:
I normally use Duracell or Energizer. Usually the E2 or whatever they're pushing as their high output cells intended for cameras and whatnot.
(Regular alkaline are quite poor.)

I think, though, that I always shoot at ISO 100 in fear of getting noise. I think if I go to 400, I can get a bit more life.

Although I do have to say that the 2500mAh rechargeables really do a number for the istD. With the istD shelved as a backup, maybe I'll give those a try.

Definetely use rechargeables.. I always wonder why, fo standard sized cells, why standard disposable cells are evn available these days. They sell for the same price as decent (Duracell) batteries, but youan use them a thousand times or more..

Cheers

Liam
Liam


"Make your hands respond to what your mind demands." Jesse James

Best wide-angle lens? Two steps backward. Look for the 'ah-ha'. Ernst Haas

MattMatic

Link Posted 26/04/2010 - 11:00
Better late than never

At the request of Ken (Gartmore), here are the images of the hack to the Pentax grip:

Taking off the cover to reveal the screws:



...another screw...



The plate and bolts that hold the hotshoe grip on. Watch the black wire doesn't break!



Slice a little off the rubber padding so you can get NiMH batteries in the holder!




Close-up view of the 'work' end. One filed out isolation area on the top right (so the digital pin isn't grounded), and one drilled locking hole on the top left to accept the lock pin of the AF540. Pay particular attention to the fact that the locking pin is in line with the bottom left pin, but the digital pin is offset somewhat (you may want to carefully measure against the dSLR hotshoe):


(Measure twice, cut once )



http://www.mattmatic.co.uk
(For gallery, tips and links)
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