What determines filter sizes

[tapas_maiti3]

Hi

 

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One thing that annoys me about Pentax is that they make very little attempt to standardise their filter sizes. If you buy your standard 3 lens kit you can easily end up with 3 different sizes which leads to a bag full of filters or (in my case) not bothering with them. It has weven affected my lens purchases.

 

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What determines filter size ? I guess there must be some correlation to the speed of the lens but if we look at these cases.

 

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1. the 55mm - 3 designs and 3 filter sizes from 82mm up 100mm !

2. the 165mm 2.8 has a 67mm whilst the f4 L/S has a 77mm

3. why would a 75mm lens need an 82mm filter.

 

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Contrast this to some other manufacturers - Mamiya RB/RZ all 77mm. Blad - B60 except for 40mm FLE and really long lenses.

 

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Whilst obviously not a reason to change makes, isn't filter size one of those design issues where the convenience of the end user i.e. the customer ought to be considered ?

 

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Tapas

 

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P.S. Steve - I like the idea of a 35mm, I would then ditch the 45mm and go for a 35 / 55 combo. I still feel that redesigning the short teles is the priority.

[marcelo_p._lima]

Hi Tapas,

 

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I agree with you that it is annoying to have different filter sizes.

I have the 45/90/200 lenses which all have different threads.

 

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It is interesting that the Mamiya RZ has all lenses in a 77mm size. I

didn't know that. I got into MF recently (been shooting w/ my Pentax

for less than 3 months now) but I know that back in November when I

started looking into MF, if I had a ton of cash to spend, I would

probably have bought a Mamiya RZ 67 Pro II because it's such an

incredible system.

 

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But I'm happy with the Pentax. Some things (filter sizes, a 35mm w/a,

closer-focusing teles) could be fixed, definitely.

 

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To go back to your original question: of course Steve will answer

this better than I, but if Mamiya can do it, Pentax could have

definitely standardized their filter sizes. If nothing else, they

could've laid down the blueprints for all their lenses and simply

picked the largest filter size of them all and stepped up the fronts

of all other lenses to match that.

 

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It would be nice if Pentax were a more "responsive" company--it seems

to me that they're not very good listeners..

 

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regards,

Marcelo

[steve_rasmussen]

Tapas, Marcelo:

Some good points here. Lens designers do not design around a given

filter size in most cases. They design to meet the perceived needs of

the photographer. The filter size is a consequence of this. Mamiya is

just a bit more customer oriented than Pentax. Maybe someday Pentax

will use customer feedback to improve their products. Most of the 67

lenses could be 82mm with the remainder being 77mm. On their next

redesign, I would propose a 200mm f/2.8, Double Gauss leaf shutter

using ED glass and 82mm filter. Discontinue the 165mm. Redesign the

135 macro to close focus without the need for tubes. Discontinue the

overpriced 100 macro. Redesign the 300 to have a tripod mount on the

barrel, closer focusing and more accurate DOF scale. Reintroduce the

non-ED 400mm to give the customer some choice in this matter.$$$$$

Redesign the 500mm to be a seven element, non-ED, superachromatic lens

with f/6.7 speed and 82mm filter. Redesign the 105mm to accept an 82mm

filter without changing the optics. Discontinue the 90mm. Etc. etc.

You get the idea. The large front element used on the 75mm

retrofocus(Angenieux, France, 1950)is used to increase the

illumination at the edge of the field. The 45 and 55mm are not

Retrofocus but are German based designs and for some reason can get by

using smaller front elements. Seventy seven mm filters could be used

in the outer bay telephotos'rear filter area(600, 800 & 400). SR

[marcelo_p._lima]

Steve,

 

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About discontinuing the 100 macro: I didn't understand why Pentax

came up with this lens in the first place! I would think a macro

would be more useful if it were more "tele" and thus gave you more

working room. It doesn't seem as if they're using any kind of

"consumer feedback" because this was a recent introduction. I also

don't understand why Pentax designed this lens to provide 1:1

magnification with an ADAPTER when the equivalent focal length Nikon

lens does this without any extras.

I wouldn't discontinue the 90mm though. I really like this lens--I

find it approximates better a "normal" lens for 6x7, and is closer to

my old 50mm in 35mm than a 105 would be. Today I got back some

chromes which surprised me; this lens also performs extremely well

wide open.

It seems as if our discussions invariably revolve around lenses; we

should start lobbying (sending mail, whatever) to make them listen to

our suggestions.

 

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regards,

Marcelo

[tapas_maiti3]

Hi Steve, Marcello

 

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Thanks for the input, Steve your lens wish list almost exactly

mirrors mine (I don't really care if the 200mm has a leaf or not

though).

 

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The lens choices seem to mirror Pentax's 35mm line, for instance the

new 100mm macro. They bought out a 1:2 100mm macro for the 35mm line

up and I wonder whether it was just cheap to scale it up for 67 ?

 

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I too looked at the RZ67II kit very strongly (same sort of price in

the UK), I think it is a better designed system but much too big to

travel with and not as fast to use.

 

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I am not sure there is any effective method of lobbying Pentax !

 

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Tapas

[michael_k._gardner1]

I agree with all of you that Pentax does not seem to be particularly

interested in getting input from the average user. I also own a Canon

EOS system, and I think Canon is the same (though they may survey

their Canon Professional Services members). I've always perceived

Japanese companies as very adept at marketing and manufacturing. But

camera makers don't seem to do a lot of market research among average

users. Perhaps they do, and I'm not aware of it; or perhaps they do

in the Japanese market. At any rate, I agree that future products

would benefit from more input from users than seems to be the case

today.

[steve_rasmussen]

Hi everyone; thanks for contributing to this forum. Without you, Phil

would erase us.

My reason for suggesting the elimination of the 90mm was because of

the price differential of the 90 and 105. They are both great lenses

though.

Scaling up lenses from the 35mm to 67 is a mistake in most cases.

The 100mm macro example is good evidence of this. Scaling up a 50mm

Double Gauss from the 35mm world to use as a wide angle 50mm on the 67

is impossible and I'm glad to see Pentax has not tried that. Scaling

up can be used with certain focal lengths however (telephotos).

I should mention a small error in my post above. The 45 and second

version 55mm are German based designs. The present version 55 is

a unique Pentax design as far as I can tell.

I will be off line from this forum between May 28 - June 11. Doing a

photo trip to the tropics. SR