pentax 67 fill flash outside, my conclusion

[game]

hi there,
I have a conclusion/question on a common issue for the pentax 67:

This camera's sync speed is 1/30 top.
If, in an outside scene, you want to underexpose the background a little and fill-in the front subject with a flash, the exposure time is most likely to be faster than 1/30, which is impossible with the pentax 67 since the sync speed is only 1/30.

I was wondering: is it possible to use a ND filter? in that way the background will need longer to be correclty (under)exposed, so a little underexposure would be possible ... I have some second thoughts on this, and i'd like you're opinion on those thoughts:

If one uses a ND filter to achieve the fillin possiblity the amount of light that will go trough the lens will be smaller. So (with the exeption of DOF) basicly the effect is the same as making the apparture smaller. Since flash intensity is affected by the aparture, a ND filter will effect the flashlight in a same way.


My conclusion: camera's with 1/30 flash sync can be used outdoors with underexposed backgrounds and filled in foreground subjects. If one remembers the following points

1. The flashlight must be powerfull enough to compensate for the loss of light.
2. You make apparture smaller, and use the fill in but than DOF becomes bigger.
3. One can maintain a small DOF, by keeping aparture big and using a ND filter ...
4. in that way, a 2stops ND filter turns a 1/30 flashsync camera into a 1/125 flashsync camera, and a 4 stops ND filter makes it a 1/500 flashsync camera.
5. off course the image in the viewfinder will become dimmer, but that's no big deal...


Is the above perfectly true?
If yes, great, if no, what's not correct?

I really hope for some responses here, cause I consider this quite essential for everyone that uses a pentax 67 or other low sync camera's that want to use flash light....

THANKS A LOT, kind regards Sam

 

[Jon Shiu]

Hi, aren't there LS (lens shutter) lenses for this purpose?

Jon

 

[David A. Goldfarb]

I sometimes use fill outdoors with my Bronica S2a, which also has a slow sync time. The key is to use a powerful flash unit (I use a Norman 200C setup). If you want to maintain a wide aperture with a bright light source, yes, use ND filters or slower film.

Point 4 is just confusing. I wouldn't try to think that way. The camera syncs at 1/30th, period. An ND filter or slower film let you use a wider aperture. Further mental gymnastics not required.

Indeed, a leaf shutter lens gives you further options (there was one for the Bronica).

 

[Soeren]

Well 1/30sec is 1/30sec no matter how many ND filters you use. The point of using fill flash is exactly "FILL" so why do you want to underexpose the background? No I do know you mean just a little, ½-1stop tops. My point is the slow shutterspeed will cause blur with moving objects which offcource isn't necessary allways a problem. The point you state about NDs open you aperture is offcource valid but I might depending on situation and subject go for a reflective screen.
Cheers
Søren

 

[game]

thanks guys for the reactions.
point 4 is indeed funky, but it kindoff works like that.
there are two LF lenses for the pentax, bt they cost a ton, and a ND filter does not. a reflective screen is possible, but 1, you will have to bring that along, and Sometimes bagage should be small as possible, and 2. Still a moving or, bright background causes trouble...

I just find it hard to believe that one would buy a LF lens only for the flashsync purpose, if a ND will do the trick... Only disadvantage I can think of is that your focussing image will be a tad darker.

If anyone feels the need to argue with the above and my initizal statement, PLEASE DO SO! if not does someone knows a good flasher, that will be powerfull enuogh to compensate for the +- 3 stops loss of light due aparture or ND? One that may fit the flash shoe on the wooden grip from the pentax??

Thanks the responses, I hope to get some more! kind regards Sam

 

[Nick Zentena]

Why would you want to underexpose the background by 3 stops? You'll end up with those cave like photos when you use flash and don't drag the shutter.

Instead why not expose the background correctly so you get a 1/30th shutter speed and use the flash to fill. Better some motion blur in the background then cave pictures.

 

[Bob F.]

The ND filter effectively reduces your film's speed by the number of stops of ND that you use so you can see if it does what you want by assuming your film is 2-stops (or whatever) slower and see if that fits in with you getting the DoF/f-stop that you want at 1/30th. It has to be said that if you do this sort of thing a lot, a lens with a leaf-shutter is the way to go: that way you do not lose effective film speed, but as you write, the expense is somewhat greater than the cost of an ND filter (or three)...

3-stops below nominal exposure is putting the background very dark in B&W and mostly in to total blackout with reversal film so you may want to consider one, or two stops at most, depending on the type of film.

Have fun, Bob.

 

[max_ebb]

The 90mm LS lens isn't all that expensive. At KEH you can get one (bargain condition) for $119 (or $126 with caps). They used to have bargain 165 LS for under $200, but now all they have is excellent for $275.

I like the 90mm LS because besides having high speed flash sync, you can also use it to do multiple exposures. You can connect a cable release directly to the lens, and re-cock/fire the shutter as many times as you want with the camera shutter open in 'time' mode (shutter speed dial set between shutter speeds).

 

[Toby Key]

I've had a pentax 67 for ten years and my solution has always been to use a large silver white reflector - this actually does a better job of 'fill' its a much nicer light. It can also be used as a main light on a sunny day by putting you subject in the shade and then 'lighting' them with the reflector - I've had great results doing this.

 

[David A. Goldfarb]

ND filters or slower film let you shoot in brighter light with a wider aperture, but this has nothing to do with flash fill. You still need a powerful flash to balance the sun, because the ND filter doesn't change the ratio between the sun and the flash.

A LS lens lets you use a less powerful flash unit for fill with full sun. The lens may be more expensive, bulkier, and heavier, but if it lets you get away with a small Vivitar 283 instead of an expensive Quantum, Norman, or Lumedyne strobe and a heavy battery pack, then the LS lens is worth it. Of course, if I'm shooting in full sun with flash fill, I'll probably use both a LS lens and the Norman, unless I'm traveling and just carrying a small flash unit.

 

[luvcameras]

ditto, the 67 lenses are not that expensive. The 90mm LS is no longer repaired by Pentax so its price has come way down. The 165LS is more modern and fetches more than the 90Ls by double. See my Pentax 67 Lens Page for more info.

http://members.aol.com/dcolucci/p67ss.htm

Thanks
Dan

 

[game]

one thing I was wondering:

are the backs prisms and lenses between the rb67 the rb67 pro s and the rb67 pro sd interchangable??

Thanks, kind regards Sam>

 

[Nick Zentena]

I think you want to put this in the other thread.

Anything older should work on anything newer. Going back might have problems.

 

[game]

you're right, thanks for the answer thuogh!
I made up my mind: I should switch systems. the Pentax has tomany disadvantages, although I love the camera....

I am going to start a new thread, because there really seem to be no arguments to either choose a bronica gs-1 or a mamiya rb67 pro-s.

Hope to get clear how those two compare.... Game