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Forum: Pentax Medium Format 10-31-2011, 01:20 PM  
67 lenses on 645D
Posted By leping
Replies: 10
Views: 4,984
DigLloyd.com has tons of information on P67 lens performance on P645D. No surprising with their larger image circles they tend to perform better than the 645 lenses except in few cases.
Forum: Pentax Medium Format 04-08-2011, 04:49 PM  
Pentax 67 55mm/f4 late lens fixed tilt modication
Posted By leping
Replies: 6
Views: 4,216
There have been recently quite a few messages asking how did I do the tilt modification on the Pentax 67 55mm/f4 late model lens, after I had it mentioned in at least one of my posts, so I am here to share my successful and unsuccessful stories.

The following URL describes one way to do it, not exactly my originally way (the author did not thoroughly understand me), and by this along it is hard to get the down tilt up to the desired ~1 degree range:

Effeunoequattro - Il Portale Della Fotografia analogica e digitale

However, after seeing his method, I recently re-worked my sample to include his mod, in additional to my original one, which went much deeper into the lens, with much more risks. It is really hard to describe, but maybe one day I should shoot a series of instruction pictures if there are enough interests, taking the risk that I can be unable to put things back one more time or break something. With now two spacers in stead of one inserted into 2 gaps, I am getting about 1.2 degrees overall, which fits my need pretty well.

Nevertheless, I volunteered to mod another copy of the same lens for a forum member, but could not loose the three inner screws no matter how hard I tried, so that I could only complete the easier "outer" mod, as documented in the web link.

Also, remember that, after the mod(s), the lens become a fixed tilt lens for only the vertical shots (unless you need a horizontal swing, and it happens to be along the right direction, i.e., the close subject is on the left side of the frame). It is fine with me, because the purpose is to help the near-far kind of composition and the down tilt is mostly needed shooting vertical. Another problem is, the original lens structure of course was not designed with such gap(s) created in mind, so the aperture ring will become very stiff, and can be adjusted only with little force.

I examined the structure of almost all the other P67 fixed focusing lenses, but found only the 55mm/f4 late has the room for mods like this, looking at the components from the rear.

Need not to say it is not a easy, a readily practical, or a perfect mod of any kind, and anyone trying this takes his/her big risks, even I managed to get one copy working great, selfishly for myself.

Unfortunately, 55mm is no longer a true wide angle on the much smaller 645D sensor (becoming 40mm in 35mm term, using the short side equivalency which makes sense to me as I print 4:5), so that the value of such tilt mod becomes much less significant in the digital age. Needless to say, a shift/tilt P67 to P45 lens adapter is what we are all really waiting for.
Forum: Pentax Medium Format 03-28-2011, 10:46 AM  
645 lens availability better now
Posted By leping
Replies: 34
Views: 6,922
Most of the P645 lenses, and even some P67 ones (45mm/f4 is an example), are struggling with edges and corners of the 33x44mm 40MP 645D sensor. It is the optimal balance point of DOF (around 1/2 stop advantage over "full frame 645"), noise (already adequate -- I would prefer to shoot at ISO 800 in most case -- just love the grainy looking), lens coverage / size /weight / cost / availability, processing speed, etc.

As far as the KEH price goes. 2 months ago Lloyd bought an EX grade 75mm/2.8 A for $159. Today it is $379. I ordered a 2x extender EX for $139 one month ago, and now it is $299. However, the current EX+ 120mm/f4 A macro at $465 is a good buy, and I wonder why it could have stayed for so long.
Forum: Pentax Medium Format 03-26-2011, 06:47 PM  
645 lens availability better now
Posted By leping
Replies: 34
Views: 6,922
Part of the reason of the KEH lens availability is they raised price, typically 2x or 3x what they did months ago.

There is a table of B&H's new P645 lens prices 10 years ago, as well as the KEH prices as it used to be, in Lloyd's 645D review. Compare to what it is there now.
Forum: Pentax Medium Format 03-24-2011, 09:15 PM  
645 tele converters on 645D - any one tried?
Posted By leping
Replies: 13
Views: 3,373
OK, I do not use PCs but I clicked the zip file link above again on my Mac. It downloaded and opened the JPEG image in Photoshop without a glitch.

Following the posted 700x1024 pixel dimension limit, as well as 700KB for JPEGs, I have to make only small crops at 100% pixels, plus a reduced size full 645D frame to show the relative scale.
Forum: Pentax Medium Format 03-24-2011, 06:01 PM  
645 tele converters on 645D - any one tried?
Posted By leping
Replies: 13
Views: 3,373
No. I don't even think there are electronic contacts on the extender.
Forum: Pentax Medium Format 03-24-2011, 11:38 AM  
645 tele converters on 645D - any one tried?
Posted By leping
Replies: 13
Views: 3,373
It is a 100% original pixel crop of a Pentax 645D digital camera test shot of a flat target, made from different pieces of cards and resolution patterns pasted on the board, nothing related to scanning of any kind, or printing size. The West Coast Imaging advertising card is just happened to be one of the contents used to fill the space, has nothing to do with scanning or printing.

I tested on a Mac, and the zipped JPEG file unzip and openned normally. Anyone else had trouble?

All the 2x converters are worse than the 1.4x, since they "split" the original resolution more. If a lens by itself can resolve 80lpr/mm, simply speaking but not entirely correct, even a perfect 2x would make it 40lpr/mm, while a perfect 1.4x can do 57lpr/mm, in theory.
Forum: Pentax Medium Format 03-23-2011, 10:19 PM  
645 tele converters on 645D - any one tried?
Posted By leping
Replies: 13
Views: 3,373
1. As predicted, the 2x basically does not do any good. However,

2. Surprisingly, with my 400mm/f5.6 ED IF lens, which is sharp by itself (see Lloyd's reviews), the Pentax 645 1.4x extender did really well -- one has been sitting on KEH for days, which I put to my card only because I was ordering something else, just wanted to try out for fun, and fully expected to return.

Here is a 100% crop off my resolution target at ( f/10 - one stop ) = f/14. Of course, together it makes a 560mm/f8. I compared the 400mm alone results upsampled to the same size, and found the 1.4x gave much more real details. Some yellow fringes, but livable with natural subjects, and probably correctable if I elaborate, so far only used the default Lightroom 400mm lens profile. I did test a Pentax 67 1.4x with my 300mm/f4 P67 ED IF M*, but I did not see results this good.

No wonder I am keeping the little thing for now. Notice the forum server compresses uploaded JPEG files, both size and quality, so it does not look 100% and as sharp as it has been, but I put a Photoshop level 10 JPEG zip file for downloading viewing.
Forum: Pentax Medium Format 03-23-2011, 12:36 PM  
645 tele converters on 645D - any one tried?
Posted By leping
Replies: 13
Views: 3,373
For example if you follow Lloyd's blogs, he recently found the Canon's new III iterations vastly better than the II.

diglloyd - Lloyd Chambers Blog

diglloyd - Lloyd Chambers Blog
Forum: Pentax Medium Format 03-16-2011, 09:12 AM  
645 tele converters on 645D - any one tried?
Posted By leping
Replies: 13
Views: 3,373
Anybody tried the Pentax 1.4x and 2x tele converters on the 645D?

I tried the Pentax 67 extenders with the 67 300mm/f4 M* ED IF lens. The results are usable with the 1.4x, but not stallar, and the contrast is low. Together it is not in the ball park of the 645 400mm/f5.6 FA performance level. The 2x results are not good.

I wonder if, for some reasons, the 645 converters may do better? If the 200mm/f4 and the 1.4x can approximate the 300mm 67 lens level, I can save quite some weight and space (although it would be only a 280mm/f5.6).
Forum: Pentax Medium Format 03-07-2011, 02:25 PM  
FA 35mm F3.5 test with 645d
Posted By leping
Replies: 39
Views: 12,041
Take a different altitute and thinking the glass is half full.

For example, if I had the 35mm lens Lloyd tested, I would be actually very happy for the little skew he has seen. Rotate to the left, and shooting vertically, it becomes a lens with little bit down tilt, just like my purposely and elaborately modified P67 55mm. My foreground would be much sharper without the needs to stop down to f/16-f/22 in a near-far composition, which is part of my shooting style, from what I can see in Lloyd's 100% crops (the left side foreground is very sharp at f/5.6, while the right side is very sharp at far greater distances). Even the shot I use as my icon on the left would benefit a little, since the rock is nearby on the left, and the mountains to the right are far away.

If I don't need the tilt (or the swing), at f/11-f/16 the results are passible on prints as well, so I actually have a little bit of the both worlds, and would not exchange it for a perfectly aligned sample. :D

Thinking things not purely technical, and be creative.
Forum: Pentax Medium Format 03-07-2011, 10:50 AM  
FA 35mm F3.5 test with 645d
Posted By leping
Replies: 39
Views: 12,041
Lloyd just published two long pages testing a 35mm/f3.5 AL FA with 645D.

diglloyd.com blog - Pentax 645D + Pentax FA 35mm f/3.5
Forum: Pentax Medium Format 02-28-2011, 02:01 PM  
400mm Lens Recommendations
Posted By leping
Replies: 17
Views: 5,767
Lloyd's test showed the Pentax 645 FA 400mm/f5.6, at least the copy in his hand, performed very well over the full 645D image frame, making it the top two in sharpness, along with the 120mm macro. Massive Moire is visible even widely open at the edges of the images, indicating the lens resolution went much beyond the sensor (Nyquest) limit.
Forum: Pentax Medium Format 02-24-2011, 07:48 PM  
645D does Yosemite
Posted By leping
Replies: 27
Views: 8,796
Wow! You had real good luck!

I used to call Yosemite Valley my "backyard" (when still in the Bay area"), and I go often enough to know the kind of fog not to form often. On my 15+ winter stays only saw it once, 12/26/2003 (the reason I can easily remember the date).

Congratulations!
Forum: Pentax Medium Format 02-23-2011, 02:22 PM  
55mm lens comparison on 645D
Posted By leping
Replies: 15
Views: 9,347
I said the very same thing years ago (experiences / tests on film), but not many believed... I sold my 75mm, 90mm, and 105mm primes too (the 55mm was kept for another use).
Forum: Pentax Medium Format 02-17-2011, 10:46 AM  
Crop factor of the 645d
Posted By leping
Replies: 16
Views: 15,732
I only print 4:5 (8x10, 11x14, 16x20, 20x25, 24x30, ...) so to me it is the short side which matters.

This way, the full-frame 35mm equivalent focus length is derived with a factor of 24/33=1/1.375=0.727, and the 55mm acts exactly as a 40mm lens on my D700, after I crop the both to 4:5.

My backbone landscape camera is a Pentax 67, for which after many years I know the "seeing" of each of their lenses. Now, I need apply (multiply) a factor of 56/33=1.7 to get the terms of 67 lens, so the 55mm gives me the field of view of 93mm lens on my 6x7 film, about the long end of my 55-100mm zoom.

For Pentax 645 the factor is 42.5/33=1.29.
Forum: Pentax Medium Format 02-16-2011, 12:05 PM  
What are 6x7 "Late" lenses?
Posted By leping
Replies: 2
Views: 2,520
Forum: Pentax Medium Format 02-15-2011, 09:38 PM  
645d Len Correction
Posted By leping
Replies: 14
Views: 2,926
Gurtch: Warped has answered your questions, and here is a picture of the LightRoom lens correction panel, where you just select the make and the lens from the lists.
Forum: Pentax Medium Format 02-15-2011, 12:25 PM  
645d Len Correction
Posted By leping
Replies: 14
Views: 2,926
I only used LightRoom 3. You turn the lens correction module ON, and select lens profile from the pull-down menu there.

Once I am home I will double check to give you more details. Thanks.
Forum: Pentax Medium Format 02-14-2011, 09:10 PM  
645d Len Correction
Posted By leping
Replies: 14
Views: 2,926
RAW Developer if you ask me. The most "film-like". But no lens corrections there (can be done later in Photoshop).
Forum: Pentax Medium Format 02-14-2011, 05:17 PM  
6x7 45mm Vs 55mm
Posted By leping
Replies: 16
Views: 14,467
Your welcome. A useful 67 lens ration, on film, can be found here (as I posted several times -- ratings in this database agrees 100% with my experiences with the 67 lenses I owned -- again, on film):

Pentax 67 Lens Guide

Notice the 45mm was not a bad lens on 56x69mm film at all, even with the little CA issue. However now we found it is only sharp over the center region on a 33x44mm digital sensor... Quite a different animal.
Forum: Pentax Medium Format 02-14-2011, 04:57 PM  
645d Len Correction
Posted By leping
Replies: 14
Views: 2,926
Lightroom 3 (and the most recent ACR) has correction profiles for most of the recent Pentax 645 lenses (totally 15 profiles for all the FA lenses). Pentax supplied these profiles to Adobe.

http://kb2.adobe.com/cps/846/cpsid_84666.html

For manual unchipped A lenses since the lens type is not recorded in the raw files, the correction is not automatic. But one can always manually select the corresponding FA lens profile in the most cases (except for, for example, 35mm and 150mm where the FA and A designs are different).

By difinition, RAW files are directly off the sensor, not something "corrected". To the most they can contain correction data (profile) but the actual job is always done in RAW conversion.

Pentaxsmc PENTAX-D FA645 55mmF2.8AL[IF] SDM AW
Pentaxsmc PENTAX-FA645 33-55mmF4.5AL
Pentaxsmc PENTAX-FA645 35mmF3.5AL[IF]
Pentaxsmc PENTAX-FA645 45mmF2.8
Pentaxsmc PENTAX-FA645 45-85mmF4.5
Pentaxsmc PENTAX-FA645 55-110mmF5.6
Pentaxsmc PENTAX-FA645 75mmF2.8
Pentaxsmc PENTAX-FA645 80-160mmF4.5
Pentaxsmc PENTAX-FA645 MACRO 120mmF4
Pentaxsmc PENTAX-FA645 150mmF2.8[IF]
Pentaxsmc PENTAX-FA645 150-300mmF5.6ED[IF]
Pentaxsmc PENTAX-FA645 200mmF4[IF]
Pentaxsmc PENTAX-FA*645 300mmF4ED[IF]
Pentaxsmc PENTAX-FA645 300mmF5.6ED[IF]
Pentaxsmc PENTAX-FA645 400mmF5.6ED[IF]
Forum: Pentax Medium Format 02-14-2011, 03:09 PM  
6x7 45mm Vs 55mm
Posted By leping
Replies: 16
Views: 14,467
From Lloyd's test results with my 67 45mm lens -- which I believe is a good copy, since I had three to pick and they are all similar, none is too bad but nothing as sharp as the newest 67 55/f4, with CAs even readily visible on film -- on 645D it is not sharp out of the center 1/2 circle.

I believe this agrees with the others reported on this Forum (but I have no time to search and quote). I can post film scan crops to demonstrate the CA issue. As we all know, the newest 67 55mm doesn't have any CA problems like this.

The conclusion was, currently the only lens sharp to the edges (at f/8-f/16) is the 45-85mm zoom at 45mm.
Forum: Pentax Medium Format 02-12-2011, 04:57 PM  
Pentax 6x7 55/4 and 67 55/4 practical differences
Posted By leping
Replies: 7
Views: 3,222
No intent to offense or disappoint anyone, but ratings on this Pentax 67 lens database agree with my personal experiences completely:

Pentax 67 Lens Guide
Forum: Pentax Medium Format 02-05-2011, 10:34 PM  
DigLloyd "highly recommended" Pentax-FA 400mm/f5.6 lens on 645D
Posted By leping
Replies: 6
Views: 3,630
Again, as expected and totally consistent with what forum members said here, the P67 55mm is stellar, but the P67 45mm is soft out of the central 2/3 area.
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