High shutter speeds

[jean_groth_]

I recently have decided to buy the Pentax 67II. Reading the post

on LUSENET has been of great help in taking that decision. But

a supprising problem, undiscussed of on LUSENET, has

popped up.

The camera shop allowed me to test the camera before

purchase: I wanted to check out the shutter. So, using a Pentax

67II on a tripod with a 90 mm lens focus on infinity, I shot a roll

on a white wall � having previously check that all the surface

included in the picture was uniformely lighted � and shoot at

1/1000 at f2.8, 1/500 at f 4.0, 1/250 at f 5.6... and so on. All the

frames from 1/125 down where uniform in density but,

surprisingly, the frames shot at 1/1000, 1/500 and 1/250

showed bands of differents densities: the frames looked like

stripes!

The camera was send to Pentax Canada Repair Center and, on

return, I tested it again... with the same results! The camera was

send back again and, with the last test roll in hand, Pentax

Canada technician said that it is normal for Pentax's horizontal

shutter to give such results at those speeds. That, if it showed

on a photograph of a white wall it won't be visible in a

photograph of a real subject (as if a sky would not show the

bands)! The camera shop tested another camera with the same

results: at high speeds the frames showed very easily visible

bands of differents densities!

Now, my question is: has anyone tested the shutter? What

where the results at high speeds? Can it be trusted? Hopefully,

my results where accountable to defectuous shutters and are

not «normals», as the technician said. I just can't beleive that

such an acclaimed camera as the Pentax 67II could not be use

with confidence at speed higher than 1/125! And, for all other

considerations, I would like so much to use one.

 

<p>

 

Jean Grothé

[milton_barrocas]

One reason for the banding may be that the shutter travel speed varies

as its traveling across the frame. This will likely result in

consistent banding in consistent locations in every frame. If however

the banding that you see is well defined but the location is

inconsistent from frame to frame then the problem could be lighting.

This effect is similar to using flash with a shutter speed faster than

the max sync speed. The P67's shutter allows for flash sync up to

1/30. Faster shutter speeds means a slit exposure so any varying light

sources will create exposure "bands". When you tested did you use

fluorescent lighting? Remember fluorescent lighting flickers heavily

at 60 Hz (most incandescent lights will also result in varying light

levels to a lesser degree). All shutter speeds above 1/30 will show

banding to some degree. Since the P67 has low sync speed it becomes

prone to this effect quicker than the 35mm cameras with very high sync

speed or leaf shutter lenses. Try the same test using daylight, if the

problem is still present then its likely a shutter travel problem.

I've used the P67II for a long time and never confronted this problem

so do not see it as a limitation.

[jean_groth_]

Thank you for answering my post, M.Barroca.

 

<p>

 

As for your questions: a) the banding pattern is consistent from

frame to frame for each specific speed and shows slight

differences between the three differents speeds (1/1000, 1/500

and 1/250); b) the setup was: camera at three feet from white

wall, lens set at infinity, with two blue lights in reflectors on each

side, all other lights closed.

 

<p>

 

If I understand well your closing statement, your diagnoctic

would be of two defectifs shutters; you don't consider this

banding as a normal phenomena for the Pentax 67II.

 

<p>

 

If so, I would then start searching for a well functionning item.

 

<p>

 

Thank

 

<p>

 

Jean

[jean_groth_]

Further informations...

 

<p>

 

I went to another store and before buying the 67II requested that

the camera was tested as to the high shutter speeds. The

manager tested two new cameras and, to his amazement, they

both had the same flaw: at 1/1000, 1/500 and 1/250 they showed

the banding patterns!

 

<p>

 

Jean Grothé

[steve_boothe]

Inside lighting with alternating current light bulbs - especially

flourescent bulbs - can give pronounced banding at any shutter speed

over about 1/60. Repeat test with blue sky.