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Author Topic: Pentax SMCP-FA 645N 80-160mm f/4.5 lens on Pentax 645D Imatest results  (Read 4565 times)
JDOAK
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« on: January 21, 2011, 09:32:05 PM »
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I recently purchased the Pentax 645D camera, as well as a new Pentax SMCP-FA 645N 80-160mm f/4.5 lens (ordered it from Japan).  I also have a Canon and a Sony system, and have learned through experience to test any lenses that I buy with Imatest, as about 30-40% of the lens copies that I get are not sharp, are decentered,

I thought I would share some quantitative Pentax 645D sharpness testing results.  You can download a spreadsheet that shows the Imatest results, by viewfinder position, for the SMCP-FA 645N 80-160mm f/4.5 lens at 80mm, 120mm, and 150mm, and by f stop.  The spreadsheet is at

http://cid-67997732cc8711ff.skydrive.live.com/redir.aspx?page=play&resid=67997732CC8711FF!227&type=5&authkey=NeXLMH7Adm4%24&Bsrc=EMSHOO&Bpub=SN.Notifications.  I also tried to attach it to this post.

I did not test all the lenses at all f-stops, so if you see NA in the results, simply choose a different f-stop in the drop down menus.  In the spreadsheet, blue signifies a drop-down menu.

Imatest is very sensitive to a number of factors, including lighting, distance to target, RAW conversion, post-processing, To normalize, I try to keep all of these items the same from lens test to lens test.  For my tests, I use Lightroom for raw conversion, Auto-Tone, Auto-White, no sharpening or noise reduction, and a Linear Curve with Black set to zero.  I also run through a series of focuses and report the highest LW/PH.  Ill see some decentering this way, but can miss some as well (this is a relatively complex topic).  Fundamentally, this approach tells me what a lens can do, and it is the same as what it will do the vast majority of the time.

Key findings:
   I got a pretty good copy of the 80-160mm lens.  I run Imatest to determine whether to keep the lens or return it.  This one is a keeper, but its not quite as good as I hoped it would be
   The best f-stop at all focal lengths, in terms of sharpness, is 9.5, followed by f11, then f8, and then f6.7.  I dont regard the sharpness at f5.6 as usable for my landscape work. The effects of diffraction are pretty large by f16.    I did not measure f13.
   Sharpness at 80mm is better than at 120mm, which is better than 150mm.  Racking out the lens all the way to 160mm resulted in significant softness, so I think the usable range for my copy is 80mm-150mm, and it is very good from 80mm-120mm.
   One measure of relative sharpness across camera systems is the average LW/PH for the lens-camera system divided by the number of pixels in the picture height.  I compared the 80-160mm zoom to my Canon 50mm f1.4 (probably my sharpest lens, and Ive got quite a few sharp lenses) and to my Canon 100mm f2.8 (non-IS lens).  I chose these lenses as they fall within the vicinity of the 80-160mm lens, which is approximately the equivalent of a 65-130mm lens for 35mm systems.  The relative sharpness of the Pentax at 80mm and f8 to the Canon 50mm lens at f8 is 91% - the Canon 50mm lens is ~10% sharper.  You might say comparing a zoom to a fixed focal length lens is unfair.  True.  The comparable figure for my Sony Zeiss 24-70mm zoom lens at 50mm and f8, the best zoom that Ive measured, is 108%.  A number > 1 means that the Pentax 645D+80n-160mm lens system at 80mm is relatively sharper than the Sony Zeiss zoom at 50mm + a900!  Given this, I believe the Pentax 80-160mm zoom performs quite well at the lower end of its range.  This metric is shown in my spreadsheet comparator.    The Pentax does relatively better (the ratio increases) at smaller f-stops.   The anti-aliasing filter (or lack of it) will also be a factor here.  
   The average increase in LW/PH for the Pentax 80-160mm lens vs the Canon lenses was about 130% (it ranged from 110% to 145%).  From just the number of pixels, if the lenses were of comparable sharpness, we would expect a 145% increase maybe more given that the Pentax does not have an anti-aliasing filter and the Canon does.  This result makes the Pentax zoom seem even weaker relative to the Canon 50mm lens.  However, a 30% increase for (approximately) the same field of view is a 30% increase, and Ill take it.
   I did not see the edge softness  to quite the same degree on the Pentax 80-160mm at 150mm as Lloyd Chambers saw, but I saw some softness that is reflected in the Imatest numbers.  I believe the difference is simply copy-to-copy variation.
   The Pentax files sharpen up very well; perhaps better than the Canon files
   For non-Imatest target shots (real world pictures), I was very pleased with my initial results

I hope that you find this interesting and/or useful.   If you do your own Imatest testing on Pentax 645  lenses, please contribute and add to this post.

« Last Edit: January 21, 2011, 09:46:09 PM by JDOAK » Logged
Leping
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« Reply #1 on: January 22, 2011, 01:57:59 PM »
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Great work.  Please note that Lloyd test the lenses at far field -- for many especially the zoom lenses the results can be significantly different from what you have tested at near field with Imatest, so the difference might not be just copy variation.  In general MF lenses have smaller sample variation that of 35mm.
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sanzari
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« Reply #2 on: January 25, 2011, 05:34:55 PM »
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Here is a UK gripe. Why can companies not set global pricing ? Does the UK have a special tax on cameras?

The 645D in the US is $9000 plus 10%tax in NYC. So $9990
In Japan the 900000 or so Yen works out at $9100 this is strength of dollar against yen.

In UK it's 9999 so that is basically $15600.

Is there really $6000 difference ? Can our dealers justify that or is it once again UK government ensuring our recession remains as long as possible in a facetious tone!

Can someone here give me an educated answer ? I am stumped. $1-2k I can almost understand. Thanks
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Davidevans
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« Reply #3 on: March 14, 2013, 11:30:00 AM »
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Late in the day to pick up on this (I was actually looking at the lens data) but the UK does have additional import duties.
On a photographic lens it is 6.7%, but on a camera I think it is 0%. The % is charged on the item cost plus shipping cost + insurance costs.
On top of that VAT at 20% is applied to the total including duty (yes tax on tax).

So the effect of import duty and VAT on a lens is an additional 28.4%. On a camera it is a straight 20%.

So on a $9000 camera the gross of VAT amount is $10,800 plus some additional VAT on the shipping and insurance costs, so maybe around $11,000.

Any remaining pricing difference between UK, US and Japan etc. should not be down to taxes.

 
Here is a UK gripe. Why can companies not set global pricing ? Does the UK have a special tax on cameras?

The 645D in the US is $9000 plus 10%tax in NYC. So $9990
In Japan the 900000 or so Yen works out at $9100 this is strength of dollar against yen.

In UK it's 9999 so that is basically $15600.

Is there really $6000 difference ? Can our dealers justify that or is it once again UK government ensuring our recession remains as long as possible in a facetious tone!

Can someone here give me an educated answer ? I am stumped. $1-2k I can almost understand. Thanks

Going back to the Imatest result posted, this relates to the individual lens doesn't it, so if there are variances between individual copies it would have to be done on each copy? I came across the post because I was thinking of getting this lens, so the comments are ivery nteresting anyway, and presumably I'm safe in thinking that although there will be individual variances, the trend is still likely to be that the wider end is better than the telephoto end?
In which case I'll stick with the (superb) 150mm FA prime for the moment.
« Last Edit: March 14, 2013, 11:38:01 AM by Davidevans » Logged
ndevlin
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« Reply #4 on: March 14, 2013, 01:34:46 PM »
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Your results precisely reflect my real-world experience.  A pretty good mf combination, but far from perfect.

- N.
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Nick Devlin   @onelittlecamera
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« Reply #5 on: March 14, 2013, 04:29:43 PM »
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The optics are from the 80's in the form of the A version the later FA only added autofocus, this zoom is to be replaced by a completely new version either in late 2013 or (more probably) early 2014.
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Slobodan Blagojevic
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« Reply #6 on: March 14, 2013, 04:47:07 PM »
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... Why can companies not set global pricing ?...

They will... one fine day, when we have global (read: equal) purchasing power, global income elasticity of demand, global spending preferences. Until then, companies will discriminate (and rightly so) based on local demand.

Alternatively, if we collectively wish it strong enough, we might resurrect the Soviet Union, this time spread across the globe, as products there often had prices permanently imprinted on them (needless to say, they were the same across 11 time zones).
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Slobodan

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« Reply #7 on: March 14, 2013, 08:19:30 PM »
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Aloha,

Funny I was going through my lenses shooting each one a little last night; as I try and figure out which lens/lenses to leave behind. I had originally thought about leaving the 80-160mm behind, but I like it a lot and tell myself I should use it more! At 2 plus pounds it was a good candidate to leave behind as I am hiking into a base camp and every pound counts. I've found this lens to be really enjoyable to shoot, and mine seems plenty sharp when stopped down, nice bohken and really great color and contrast even without a CPL. I have never shot a published piece with this lens but hope to use it on this trip, heck I'm already hoofing in 80LBS what's another couple of pounds!
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tsjanik
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« Reply #8 on: March 15, 2013, 07:26:58 AM »
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................................................... the trend is still likely to be that the wider end is better than the telephoto end?
In which case I'll stick with the (superb) 150mm FA prime for the moment.

Weakness at the long end has been widely reported.  Since I have the 75mm, 120mm and 150mm (all excellent), I had little interest in this lens; nonetheless, I recently purchased one (the price was too good to pass) and I must admit I'm surprised at how good this lens appears to be.  In situations were a zoom is preferable to a prime, I don't think you are losing much.

Tom
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