Optical Aberrations VS Shutter Vib.

[steve_rasmussen]

For many years Pentax has been accused of having optical problems when compared with other MF companies. There have been reports of the 300mm Takumar/Pentax of being hopelessly soft and that the 105 was no better than junk wide open and at f/4. Some have claimed that they have yet to get a sharp image from the 400 Takumar. Others have sold their entire P67 system because they felt the optics just didn't match other producers. My conclusion is this: Most claims of optical problems were actually caused by shutter vib. None of my eight lenses are junk wide open although the 600 will fringe quite easily given the wrong circumstances. Most of the perception of poor optics are actually the operator not knowing the limitations of the camera system. SR

[alex_b.]

Yes, shutter vibration. But when you have a job to finish and do not

have the ability to dampen the vibration (in fashion you mostly just

don't have time) all that matters to art directors are end results. No

excuses like "My lenses ARE pin sharp, it's just the camera..."

I however still love the 67, although it has let me down several times

now in terms of sharpness reduction via shutter shake. No problems

otherwise, thank god, but I was forced to buy the 645n in addition to

the 67 system and love it just as much. Been using the 67 lenses on

it, yummy, and can confirm they really ARE pin sharp.

 

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But my point is - what good is a sharp lens if you have difficulties

using it, i.e. achieving it's optimum performance because the body

literally jumps when the shutter trips?

[bill baker]

The disappointing thing is that the Pentax engineering staff doubtless

think they've already answered this problem with the shutter/mirror

improvements in the 67II body. I bet they even had some lengthy

discussions about whether to try increase flash sync versus

concentrating on quieting the shutter during the design process. For

all the improvements, though, the results of the shutter redesign are

pretty disappointing when compared to the current state of the art.

Top of the line 35mm SLR blade shutters achieve, what, an order of

magnatude less shake? Even with 4X image area to shutter, I can't

believe that Pentax engineers couldn't devise a better shutter system

for the 67II given the modest spec. of the system (1/1000th top speed,

1/30th flash sync). Cost was doutbless an issue, but again, compared

to 35mm SLR's, the price/performance ratio of the 67II shutter is

nowhere near what smaller bodies achieve.

 

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I recently inherited my Dad's venerable Nikon S2 rangefinder. At equal

shutter speeds, with the 67II's mirror locked up, the S2's shutter

"shake" is astonishing slight compared to the 67's. Yes, the 67's

curtain shutter is four times the size of the S2, but the S2 is a forty

year-old design! To me that indicates that, if Pentax wanted to stick

with a curtain shutter for reasons of economy, they still could have

designed a better-damped one.

 

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I'm happy with the sharpness of my shots using my 67II handheld, but I

don't have anything longer than the 165mm in my bag and compromise on

film speed rather than shoot slower than 1/90th. I have noticed my

tripod-shot negs have gotten appreciably sharper since I shelled out

for the herkin' Gitzo 1410 and Arca-Swiss B1. But the price margin I

paid for the monster legset and ballhead, over a more modest setup,

would pay for half a new 67 lens. That's money out of Pentax's pocket.

And though I'm drooling over the new 300mm (not because of the ED glass

but for the much shorter min. focus), there's no way I'd lay down two

kilobucks (and change) for one without being able to shoot with it on

one tripod.

 

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Steve, you've written a number of times that Pentax doesn't seem to

respond to customer input. Seems to me what the 67 line needs more

than anything is a savvy product marketing guru focused on the USA/Euro

sales market, someone with the clout to get the Japanese home office to

focus resources on the true priorities of the customer base.

[joachim_inkmann]

Bill, I can not completely agree with you points. Anyone starting in

medium format photography should anticipate the costs of a high end

tripod. Amateur photographers do not change into MF because they

expect fast and cheap cameras but because they want to improve their

image quality. For this goal a sturdy tripod is simply unavoidable and

I have no problems when it costs as much as my 90mm lens.

 

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To your S2 comparison: Accidentally, the old Nikon S2 is my only 35mm

camera, so I know this little gem. If you compare the shutters of

these two cameras it is immediately obvious that it must be MUCH more

difficult to dampen the Pentax shutter. In addition, if you compare

the slides of the 45 years old Nikon and the Pentax 67II you will

confirm that the Pentax engineers have learned something during the

last decades. The current optics are much better.

 

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Having said this, I also wish that it would be possible to get pin

sharp results without all the tripod/MLU hassle. But every camera

system has its compromises and you have to find the system with the

least disavantages for your own kind of photography.

[manderioli_roberto]

If I remember well, a square shaped object inertia is heavily

dependent upon its fisical dimension elevated at the second power.

This is referred to an object rotating about an axis but actually I

don't know what the shutter of the 67 case is. I can suppose it has a

mixed movement linear-rotational. In any case the rotational inertia

component could become 16 times greater if fisical dimension

increase 4 times. That is maybe why it is not fair to compare 35mm

shutters with huge 67 ones.

 

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Just my 2 cents

Roberto

[steve_rasmussen]

The shutter vibration causes a harmonic in the long lenses and tripod

that is similar to a tuning fork. This just aggrevates the situation

already caused by the linear motion of the shutter. SR