DA* lenses may actually use quite alot of metal in them

*Lance B* · 05-13-2008, 12:05 AM

This thread was prompted by a post made over on the DPReview forum about why the DA* lenses seem to be made of plastic. I did a comparo of the lenses by their specs and this may not actuallty be the case.

Basically what i wrote on the DPReview forum here:

The FA*300 f4.5 has been described by some as having a plastic casing and metal components internally. I really don't know as I don't want to scratch back the champagne coloured paint to find out. ;-)

Now, as a comparison, the DA*300 f4 is about 150gms *heavier* than the FA*300 f4.5 and the extra 150gms may account for the extra weight due to the fact that the DA* is 77mm front element and the FA* is 67mm front element, *but* the FA* has 9 elements and the DA* only 8 elements, so glass may not be a contributor to the weight difference.

If that is the case, then why are they essential the same weight considering that the DA*'s barrel is definitely plastic and the FA*'s barrel *maybe* plastic. In my view, the DA*300 *must* have internals very much the same as the FA* lens which would then indicate the extensive use of metal and why they weigh a similar amount.

The same can be said for the FA*200 f2.8 as compared to the DA*200 f2.8 as the DA*200 f2.8 is actually 40gms *heavier* than the FA* counterpart and we definitely know that the DA*200 uses a plastic barrel!!

I am not entirely convinced that the internals of the DA* zooms do not use metal, in fact I bet the use quite alot considering their weight compared to the *ALL* metal zooms that Pentax made.

If we look at the DA*16-50 f2.8, it is only the third heaviest zoom behind the FA*28-70 f2.8 and the completely *ALL* metal 28-135 f4, and this is considering the DA*16-50 is for APS C!! The APS C only DA*50-135 f2.8 is also quite a heavy zoom when compared to all the *ALL* metal zooms that are available with 67mm front elements like the 35-210 f3.5-4.5 - 17 element lens.

joele · 05-13-2008, 03:47 AM

Disasemble and let us know ;-)

I can't believe its 200gm heavier than my F*300? Thats one solid heavy metal beast, now its one light little lens in comparison ;-)

creampuff · 05-13-2008, 04:13 AM

The SDM motor of the DA* lenses must weigh something.

**Peter Zack** · 05-13-2008, 04:27 AM

And I don't know what the fuss is about anyway. Plastic composites in some ways are better. If the lens undergoes temperature shifts (hot or cold days), A plastic composite will not expand or contract as much as a metal part. The internal slides for zooming and focus are metal in all these lenses I'm sure just so they last longer. I took apart an F SMC 70-210/4-5.6 and the outside barrel was plastic composite but all the guts were metal.

Last if you are building a lens that is designed to be water and weather resistant, metal either corrodes or oxidizes. Plastic has very few issues with the weather.

*borno* · 05-13-2008, 05:09 AM

The barrel of my DA* 300 sure feels like metal to me, especially when it gets cold. except for the lens hood- not that it matters, I sure do like it

*Lance B* · 05-13-2008, 05:58 AM

Originally Posted by creampuff

The SDM motor of the DA* lenses must weigh something.

They do weigh something, but as I am involved with the electronics game, I know those micro motors weigh next to nothing.

*Lance B* · 05-13-2008, 06:01 AM

Originally Posted by Peter Zack

And I don't know what the fuss is about anyway. Plastic composites in some ways are better. If the lens undergoes temperature shifts (hot or cold days), A plastic composite will not expand or contract as much as a metal part. The internal slides for zooming and focus are metal in all these lenses I'm sure just so they last longer. I took apart an F SMC 70-210/4-5.6 and the outside barrel was plastic composite but all the guts were metal.

Last if you are building a lens that is designed to be water and weather resistant, metal either corrodes or oxidizes. Plastic has very few issues with the weather.

You are quite correct, Peter.

I merely posted this observation to try to appease those that are panicking about the fact that the DA* lenses can't be as good as the FA* versions because they are made of plastic. It's the old "Can't be as good as they are plastic crap and not like the good old metal lenses of the past" line.

I actually like the new lenses as they will not get scratched as easily as my painted metal barelled FA* lenses.

*Lance B* · 05-13-2008, 06:05 AM

Originally Posted by borno

The barrel of my DA* 300 sure feels like metal to me, especially when it gets cold. except for the lens hood- not that it matters, I sure do like it

There was some argument about whether the FA* lens barrel was made of metal or plastic. One DPReview forum member swears black and blue that they are plastic and I thought like you that they are metal. I also believe that the hood is metal too. In fact, those FA* hoods are a real work of art. Beautifully finished off with that velvet inside and the little rollers for the lens locking.

*Lance B* · 05-13-2008, 06:07 AM

Originally Posted by joele

Disasemble and let us know ;-)

I can't believe its 200gm heavier than my F*300? Thats one solid heavy metal beast, now its one light little lens in comparison ;-)

LOL. No disassembly allowed!

I was very surprised at the size and weight of the DA*300. As you say, the F*/FA*300 now looks like a baby lens in comparison!!