prism and lens attributes

[larry_johnson]

After more than 30 years in a monogamus Nikon relationship, I've

decided to have an extended affair with a Pentax 67, following a

recent fun two-day rental of a body and the 45 and 150 mm lenses. Can

someone please help me with a better understanding of two points:

what is a Beattie screen and does it really help (middle-aged eyes,

you know), and why don't I see Pentax talking about "low dispersion,"

"apochromatic" and "aspherical" glass/lens design? These seem to be

important to 35-system lensmakers -- why not to Pentax and this

(apparently) terrific 6x7? For general scenic use, which two or three

lenses are the sharpest? I'll welcome any editorial or scientific

comments.

[steve_rasmussen]

Larry, Pentax does have a couple of lenses that are designated ED,

which is their proprietary name for low dispersion glass. As far as

APO is concerned, Pentax has obviously opted not to use this ambiguous

term. Just because a lens is corrected for three colors at the film

plane is no guarantee of a small secondary spectrum. Aspheric surfaces

can indeed completly correct out spherical aberration but Pentax

realizes that for the past 150 years this aberration has been

corrected so well using spherical surface that it is not all that

necessary to use expensive aspheric surfaces(ellipsoidal,

hyperboloidal, Schmidt etc.). Pentax uses traditional methods to

correct this aberration(lens bending and high index glass). The

results speak for themselves. The 55mm and the 75mm are both ultra

sharp and neither use any special designations. Both are great for

scenics. It seems that many 35mm camera producers use the terms APO

and aspheric more as marketing hype than anything else. IF YOU ARE

INTERESTED, check out the P67 only site, greenspun.com/bboard and

page down to the Pentax67 SLR forum. SR

[gene_crumpler6]

I can't comment on Pentax's marketing strategy. I think that work of mouth, rather than advertising is the p67's strength. I own a new 55mm f4 and I can give you an unqualified recommendation. It as a super sharp lens that is fantastic for landscapes as well as general shooting. The older 55mm f3.5 is not the same design lens.

 

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My next lense will either be the new 100 macro or the 135 macro. The 105mm lens is sharp at optimum(f5.6), but really falls apart at f16 and f22(a coke bottle on your nikon is about as good). By comparison, the 55mm holds up very well down to f22. I would not recommend the 105mm or the 90mm "normal"lenses if you are looking for an all around field lens.

 

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The jury is still out on the 200mm. I'm beginning to think that my 80-200 f2.8 ED AF on tech pan can do a better job in the sharpness department than the p67 200mm on T-max 100.

 

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I've been a nikon user for 30 years and love the p67. But I've not sold any of my nikon gear either!

[patrick_drennon]

I own the 45 /f4 that you rented and use it more than any other

(105, 165LS, 600)I own. I do not do many landscapes (I live in West

Texas, good landscapes are few and far between, it is NOT an

attractive desert). If I did I would probably have the 55 instead of

the 45. The 45 is rectalinear but it is a 90 degree coverage lens and

therefore tends to destort perspective quite a bit (which is exactly

what I like about it).

 

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Steve R., who is one of your respondants is very articulate and

educated on P67 glass and has described some of the long lenses as

'super-apochromatic'. I personally do not know what this means but

interpret it to say they couldn't be better corrected for chromatic

aberrations. I know that I am totally hooked on the system and

encourage you to continue your education on it. I am particularly

impressed that you rented and test drove before buying. EVERYBODY in

this forum recommends that you approach it in that way.

 

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As concerns image brightness, I have little trouble with the Pentax

screen so have not been tempted to have it changed but others swear by

the increased brightness in the Beattie screens. The upcoming (B&H

says in 1-2 months) P67II is rumored to have a 2-3 stop brighter

screen that is user interchangeable so you may want to wait and check

it out. You are going to get many responses (these types of threads

always generate alot of opinion). Most opinion will guide you to the

55 and 75 for sharpness but I have trouble believing they could be

significantly sharper than the 45 and 105 I own. Fact is, if you pick

any of the P67 lenses with the possible exception of the 200 you will

likely be blown away by your images. Have fun figuring it out!

[allan_jamieson]

I own 6 different Pentax 67 lenses and am very happy with the quality

of them all with the possible exception of the 200 mm lense, which is

not quite as sharp as the others that I have used.

 

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For shooting Landscapes which is what I do mainly, I use the 45mm,

55mm, 75mm & 105mm mostly and occasionally the 135mm if I want a

tighter crop on something. The 55mm lense f4 version is definitely a

must have, if you are serious about Landscapes. I bought the 45mm

lense recently and like it a lot, it is a very sharp lense and it

gives a much wider view over the 55mm than you might expect.

 

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I have taken some very dramatic photographs in the Scottish Highlands

with the 45mm. If you wanted to start off with say two lenses, a 55mm

and one of the two standard lenses wouldn't be a bad idea. I have the

105mm lense which as you will probably read elsewhere on this forum,

performs best at wider apertures, down to about f11, after that

forget it. The 90mm lense might be a good compromise, if you didn't

want to buy the 75mm lense. You could get some pretty good shots with

just those two lenses, maybe adding on a 45mm sometime later.

 

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You might not think it, but the standard 105mm lense is a very useful

lense indeed. I use it and the 55mm most often, followed by the 45mm,

the 135mm, 200mm and then the 75mm. There isn't anything wrong at all

with the 75mm lense, it is maybe just a bit too in between for my

liking, it isn't all that wide angled and it's just a little wide for

a standard lense. It might suit your style of photography very well

indeed, try one if you ever get the opportunity.

 

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As regards the Beattie Intenscreen for the Pentax 67, I have one of

those in my camera, and it is much brighter and easier to see through

than the original Pentax one. Mine is also gridded, which makes it a

lot easier to line things up properly. I would also advise you to get

a handgrip for your camera, the handling is so much better with it

and you can also add a small spirit level to the flash shoe on the

top of the grip. If nothing else it looks very impressive !