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Forum: Pentax SLR Lens Discussion 12-30-2019, 07:27 AM  
Opinion time: what are your favorite manual lenses?
Posted By whojammyflip
Replies: 184
Views: 11,867
That second picture, black and white, has incredible sharpness and bokeh at the same time. That looks like an amazing lens.
Forum: Pentax SLR Lens Discussion 12-30-2019, 06:25 AM  
Opinion time: what are your favorite manual lenses?
Posted By whojammyflip
Replies: 184
Views: 11,867
If its the M 28/3.5 and the M 50/1.7, you will struggle to find better. The M 135 is no slouch either. Great set up.
Forum: Pentax SLR Lens Discussion 12-30-2019, 02:53 AM  
Opinion time: what are your favorite manual lenses?
Posted By whojammyflip
Replies: 184
Views: 11,867
My Pentax M 85mm f2 is just incredibly sharp from f4 onwards.

Here are MTF curves from f5.6 at about 4m or 50 focal lengths.

Forum: Pentax SLR Lens Discussion 12-30-2019, 02:45 AM  
Recommend 3rd Party Lens Hood
Posted By whojammyflip
Replies: 16
Views: 834
Keep an eye out for the Schneider B&W metal hoods. Things of beauty. Not cheap, but very well constructed.
Forum: Pentax SLR Lens Discussion 12-30-2019, 02:36 AM  
Interesting Lens Test
Posted By whojammyflip
Replies: 12
Views: 1,332
Anyone looking into doing tests for sharpness would be well served by the MTF Mapper software, which is easily installed, and has test target print outs.

MTF mapper download | SourceForge.net

Slanted edge testing will give much greater insight into resolution characteristics of lenses, across the entire frame.

Its pretty quick to do, but you need to be able to print test targets which are totally flat (ie mount on a chip board and screw to something solid) and measure about 1m wide.
Forum: Pentax SLR Lens Discussion 02-24-2019, 05:29 AM  
MTF Mapper
Posted By whojammyflip
Replies: 10
Views: 1,269
Nope, I have just beenevaluating lenses against each other. The next possible test is to mount some enlarger lenses and profile them...could give Ctein a run for his money. One thing is clear, there is a good reason for the "f8 and be there" phrase. Except for the Pentax M 85mm....that lens peaks in certain respects at f4.

The most controversial result I have had is for the Tamron 278D at 135mm f8 to f16. Wide open its a bit of a stinker though and the extremes are not good.

I have just posted this in the lens review section:

Tamron 278D at 135mm f8, MTF25 resolution


Tamron 278D at 135mm f8, contrast at 20, 40, 80lpmm


---------- Post added 24th Feb 2019 at 12:49 ----------



This is my kind of expertise. I work in analytics and this is fun for me.

The next step would be to just do the MTF calculation on the MTF Mapper targets, and get an aggregate reading for contrast at say 40lpmm, across the frame, in order to be able to rank lenses on a single metric. I think 100lpmm might make more sense as this is the around the limit for the sensor/film resolution. The trouble is that most lenses score zero at this spatial frequency. That Tamron is exceptional.
Forum: Pentax SLR Lens Discussion 02-23-2019, 05:56 AM  
MTF Mapper
Posted By whojammyflip
Replies: 10
Views: 1,269
Some MTF curves for primes at f4, interesting to see little or no difference between the M 50 1.7 and 1.4. Using MTF Mapper on an A1 grid, as PEF files.

Pentax M 50 f4 at f4


Pentax M 50 f1.7 at f4


Pentax M 50 f1.4 at f4


Pentax A 50 f2 at f4
Forum: Pentax SLR Lens Discussion 02-22-2019, 08:58 AM  
MTF Mapper
Posted By whojammyflip
Replies: 10
Views: 1,269
Here is a comparison of the Pentax M 28 2.8 at f4 vs the Pentax M 28 3.5 *wide open*

Pentax 28 2.8 at f4:


Pentax 28 3.5 *wide open*


I've literally just shot around 200 shots, so I am not going to post the lot. I also have the Pentax M 50 f4 and the Pentax A 50 f2 which I am going to compare with the M 50 1.4 and M 50 1.7.

This train is leaving the station! I have been meaning to get around to quantifying the performance of the Pentax lenses for a while, using MTF testing. So here it comes, watch this space.
Forum: Pentax SLR Lens Discussion 02-22-2019, 01:54 AM  
MTF Mapper
Posted By whojammyflip
Replies: 10
Views: 1,269
Hi, I have got up and running with MTF Mapper, printed a grid target and am performing some MTF testing. It generates MTF curves, ie contrast at chosen resolutions 10, 20 and 40lpmm. I am running through testing of 31 lenses at the moment, at each marked f stop. My most interesting results have been:

- Pentax M 85mm, sharp wide open, and hits peak average sharpness at f5.6, with contrast across the frame of over 63% at 40lpmm
- Vivitar Series 1 v1 70-210mm, sharpest lens at 210mm at any aperture with average contrast of 50% at 40lpm at f5.6
- Tamron 278D 80-210mm, sharpest lens at 135mm at f11 with average contrast of 64% at 40lpmm

I particularly like the slanted edge MTF testing on a grid, as its a quick way to profile a lens across the image plane.

Here is the result for the M 85mm at f5.6:


Here is a list of lenses I have for testing (cannot mount the Vivitar S1 35-85 at the moment as its rear flange hits the K7 body):
Pentax DA 18-55 AL
Pentax M 75-150
Pentax M 80-200 v1
Vivitar S1 V1 70-210
Vivitar S1 V2 70-210
Vivitar S1 V3 70-210
Tamron SP 70-210 19ah
Tamron SP 70-210 52a
Tamron SP 60-300 23a
Kiron 80-200 f4
Kiron 75-150
Vivitar S1 35-85
Vivitar S1 28-90
Tamron 28-105 179D
Tamron 80-210 278D
Pentax F 80-200
Tamron SP 28-135
Tamron SP 28-80
Tamron SP 24-48
Pentax M 24-50
Pentax FA 28-70
Tamron 28-80 77D
Sigma 21-35
Pentax M 135
Pentax M 85
Pentax M 50 1.4
Pentax M 50 1.7
Pentax M 28 3.5
Pentax M 28 2.8
Tamron SP 90 2.5
Pentax M 200
Forum: General Photography 08-29-2018, 12:03 AM  
How fast is your PC - and should I upgrade mine now Ihave a K3-ii?
Posted By whojammyflip
Replies: 29
Views: 1,830
I would buy an entire desktop on ebay, in a box. Thats the best way to get a decent PC in my opinion. Anything faster than 50% of the top CPU Benchmark score is a waste of money, unless you are either gaming or someone else is paying. I'd stick to something from generation 6 or more recent. Watch out for 'socket' compatibility if you want to be able to upgrade, and stick to DDR4 ram.

I recently sold a i7 970 based pc on ebay for something like 150 pounds (could have been 170 - but the guy got a great deal), with 16gb of ddr3 ram, and a SSD drive. I think the buyer was pretty chuffed. It was in an Antec box, which makes a big difference. I wasn't miffed about this as I picked up a i7 6600 with 32gb of ddr4 ram and asus board in a fractal design case, with a Samsung m2 500gb drive for 500 pounds.

I think the motherboard is important, and I stick to Asus boards. There may be some brand snobbery, but there is little point in saving a tenner on the framework of the computer, which limits the speed of transfer of data between components. I dont muck about with fancy cooling systems or fans and lights.

One way to make your computer go further is to switch to Ubuntu, which uses less RAM than something Windows based.
Forum: Film Processing, Scanning, and Darkroom 12-16-2016, 02:07 PM  
Can anyone recommend a good scanner-(convert film to digital)?
Posted By whojammyflip
Replies: 33
Views: 5,421
I have a Canoscan 9000f and in comparison to a shot with a DSLR such as the Samsung gx20 of a negative in a LPL metal carrier, the Canoscan is terrible....the advantage of the Canoscan is that I can do around 200 images in an evening whilst doing other things at the same time....so for high resolution, a shot on the lightbox is prefered, but for speed the Canoscan wins handsdown. Both solutions are cheap.

you can have quick, cheap, good....pick 2
Forum: Film Processing, Scanning, and Darkroom 12-16-2016, 02:04 PM  
Scanning Pentax 645 film
Posted By whojammyflip
Replies: 37
Views: 6,210
may be possible to be able to take several shots of the same negative using a digital body, and then average the results to get a higher resolution, imagine if you could shift the negative relative to the body half a pixel along....you could double the resolution
Forum: Pentax SLR Lens Discussion 12-16-2016, 01:45 PM  
Lens Reviews A28 vs F28
Posted By whojammyflip
Replies: 28
Views: 2,062
side by side comparisons are easier to evaluate as you are not looking at an absolute measurement, rather a relative judgement is being made

in this respect, the 28mm f3.5 m series lens is miles sharper than the 28mm f2.8 m series v1 lens, as I have tested these two on tmx film on a tripod, with an Edmund resolution target, and then looked at it through a nikkor 50 2.8N and a 25x scope, achieveing 250x magnification

under these circumstances, I think its fair to say an objective measurement was taken and the 28mm 2.8 literally had about 60% of the resolution of the 28mm 3.5
Forum: Pentax SLR Lens Discussion 04-20-2016, 02:26 PM  
FA 31mm f/1.8 Limited price jump since K1 announcement
Posted By whojammyflip
Replies: 13
Views: 2,281
Contrary to the optimism about prices, I picked up a mint 85mm f2 prior to Christmas for less than GBP 100, when they used to go for 1.5x or 2x that price.

Looking at the Pentax primes for cropped sensors, I think its possible that Pentax will provide new lenses for the full frame camera. If they dont, then maybe companies like Zeiss and Sigma will.
Forum: Pentax SLR Lens Discussion 04-17-2016, 07:02 AM  
Pentax-A SMC 50mm F/1:2 vs 1.2 (K Mount)
Posted By whojammyflip
Replies: 10
Views: 2,236
I've got the 50mm M series 1.4 now and got rid of the M 1.7. I also have an A series 1.7 and A series f2. Practically, they are all sufficiently sharp for general usage.

However, the 1.4 is noticeably sharper than the 1.7, between say f2 and f5.6. I've compared the M series 1.4 and 1.7 on Edmund res test charts, and the 1.4 was measurably sharper. I've seen similar differences between the 35mm 2.8 and f2 lenses (with the f2 being sharper) and the 28mm 2.8 and 3.5, with the 3.5 being sharper.
Forum: Pentax SLR Lens Discussion 03-21-2016, 03:25 PM  
SMC Pentax 1:2/28: the poor man's Distagon?
Posted By whojammyflip
Replies: 108
Views: 40,437
I keep track of lens prices, in case I should ever find a GBP 400 note down the back of the sofa, and happen to see a rare Pentax lens. I have seen the Pentax 15mm and 18mm lenses hover around GBP 400. It would seem reasonable to expect the Pentax 28 f2 to do the same, but I have seen it go for about GBP 350. At the moment, this is equivalent to something like USD 600 or USD 700. Its really quite expensive when you consider a Zeiss 85 f1.4 or 18/4 for the CY mount is around GBP 400.
Forum: Pentax SLR Lens Discussion 03-21-2016, 03:14 PM  
Resolution is not the same as IQ, not even close.
Posted By whojammyflip
Replies: 54
Views: 4,638
Pentaxforums has stepped up a gear. I note that the original poster is on my ignore list, having logged in.

Something piqued my interest here, its a real flame war thread I think.

My two penneth worth would be that the factors you have mentioned such as light and composition are being conflated with the difference in resolution. If a shot has been taken hand held at close range, neither lens will be limited by resolution thanks to camera shake, which impacts shots even at 1/500.
Forum: Pentax SLR Lens Discussion 02-25-2016, 11:33 AM  
Pentax M 20 f4 on Full Frame
Posted By whojammyflip
Replies: 21
Views: 2,744
Its the 24/2.8 which I tested: I was testing this using TMAX film in a Pentax MX, and got over 100lp/mm, based on an Edmunds optics resolution target and central resolution only. I was using a focus scope under and enlarger with the head wound all the way up and then reading the groupings off and backing out the resolution. Its not necessarily the most accurate, but it does give you a good relative measurement vs other lenses. I've not done this for ages. I need to get round to putting a script together in some software to share so that people can do MTF testing for free.
Forum: Pentax SLR Lens Discussion 02-23-2016, 01:54 PM  
Pentax M 20 f4 on Full Frame
Posted By whojammyflip
Replies: 21
Views: 2,744
The median price of a M 20mm on an ebay auction has been 180 pounds including postage, over the past few years. EUR 350 therefore looks steep. EUR 260 may be more reasonable/realistic/fair. You have to figure, this is a very wide perspective. I have used the 24mm K series prime and its the sharpest lens I have tested, in the centre, sharper than the M 28 3.5.
Forum: Pentax SLR Lens Discussion 02-23-2016, 01:46 PM  
Pentax K 28mm f2 or Carl Zeiss Distagon T* ZK 28mm f/2 lens for Pentax K
Posted By whojammyflip
Replies: 100
Views: 21,039
I think this price rise has possibly been priced in. This fabled full frame body has been speculated about on Pentaxforums for quite a while. Lenses like the 85mm M series are now cheaper than they were a couple of years back (I just picked up my second copy of this for 100 pounds, when I bought the first for 150 pounds about 5 years ago), and thats after the full frame has been announced.

Its interesting to look at the lenses of the dead mounts like Konica, and to see the 15mm wide angle going for about a third of the Pentax equivalent. Pentax lenses have already risen pretty high.

I think most people want autofocus lenses, and if Pentax release some autofocus primes, the cost of the better manual primes may actually fall. It would suit me, I rather regret having sold a M 28 f2. I've got the 35, 50 and 85 in the fast versions. Its just a shame that Pentax didnt release as part of the M series a fast 135, with a bigger ring like the 200.
Forum: Pentax SLR Lens Discussion 02-20-2016, 05:57 AM  
Pentax K 28mm f2 or Carl Zeiss Distagon T* ZK 28mm f/2 lens for Pentax K
Posted By whojammyflip
Replies: 100
Views: 21,039
for anyone interested, I've just seen a K 28 2.0 "hollywood" on ebay:
Pentax K SMC 28mm F2 / F2.0 Very Rare Prime | eBay

its beyond my budget/wife's threshold for acceptable purchases, so I am not buying it...I've had the M 28/2.0 before, and decided that the lowly 28/3.5 was sufficiently sharp (a lens which is really sharp is the k 24/2.8)

i've got nothing to do with the sale, I just thought it might be nice to give the heads up to people on Pentaxforums
Forum: Pentax SLR Lens Discussion 12-07-2015, 02:12 PM  
35mm vs 50mm usage
Posted By whojammyflip
Replies: 14
Views: 2,506
on digital, 50 will behave like a 85mm lens on film...quite a nice perspective for portraits

for general shots, some might say something shorter than 35mm might be more useful as you can get more in
Forum: Pentax SLR Lens Discussion 12-07-2015, 02:01 PM  
Macro: 50 or 100? Best "General?"
Posted By whojammyflip
Replies: 25
Views: 2,026
for what its worth, I've got a book on classic lens design from Neblette, and the Apo Skopar has an identical layout to the Pentax M 100 f4
Forum: Pentax SLR Lens Discussion 10-24-2015, 06:45 AM  
rare lens alert 1000mm
Posted By whojammyflip
Replies: 7
Views: 1,323
Just seen there is a rare 1000mm f8 Pentax lens up for grabs on Ebay. I've got nothing to do with the auction, but its a rare one I thought I'd give everyone the heads up on.
Forum: Pentax Camera and Field Accessories 01-02-2015, 12:31 PM  
B+W lens hoods
Posted By whojammyflip
Replies: 1
Views: 942
Anyone know where to get hold of B+W/Schneider metal lens hoods in the UK, please? I am looking out for some 58mm ones for my Pentax 645.
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