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Forum: Pentax Medium Format
08-08-2011, 12:36 PM
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My copy seems very good at f2.8, but decidedly better by f3.4. One issue to check is if focus plane of your lens is off, and this error is masked by the increased DOF at smaller apertures. That is, your lens may need focus adjustment at f2.8. When I want to shoot 'wide open', I do it at f3.4.
Most every lens made is only centrally sharp wide open (soft edges) and also has lower contrast. These imperfections diminish with stopping down, being optimum for most all lenses about 2-3 stops down from wide open. Rarely are lenses diffraction limited wide open. (I can think of one in particular by Leica: the 280/4 APO---was sold for around $4000; this is seen on the MTF plots as decreasing MTF as lens is stopped down from wide open.)
The whole issue is simple optics vs cost; Pentax lenses are not that expensive. The digital sensors magnify these imperfections (less of an issue with film, also masked, but by film's limitations). Even my copy of the Pentax 645 600/5.6 is better at f8 than f5.6, despite it being a rather expensive lens. It is still not diffraction limited.
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Forum: Pentax Medium Format
06-14-2011, 06:31 AM
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Aboudd,
I had same reaction with my Contax 645 and Superrotator lens. I never used it once aside from testing, and later sold it.
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Forum: Pentax Medium Format
06-12-2011, 07:05 AM
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I recently modified a late P67 45mm lens (not 55). It was actually very easy. I followed Leping's suggested method for the 55mm lens (see above links). I removed the center black plastic cover and then unscrewed the mounting plate. It does not have to be completely removed, simply lifted off about 20 degrees over the 2 mounting screws where you wish to place the shim. The shim can then be slipped in, between the chosen 2 screws, and the mounting ring re-positioned, followed by replacement of the black plastic shield with it's 3 screws.
I chose to shim opposite from the vertical tripod mount position (so tilts are vertical---portrait style). I placed a 1.65 mm thick plastic fragment (about 3 x 4 x 1.7mm) between the pair of mounting ring screw holes. Care must be taken to not over-tighten these screws, esp the ones away from the shim position. If you over-tighten, the mounting ring distorts and you cannot mount the P67/P645 adapter.
The 1.65mm shim gives about 1.2 degrees of tilt when using the 45mm lens on the P645D (an effective focal length of about 35mm). This is exactly what is needed for Scheimpflug tilts when the camera/lens is 6 feet off the ground and the subject is the ground receding to infinity.
If the subject is 1.5 feet off the ground (say a field of flowering plants) and the camera is still at 6 feet, the subject plane difference is now 4.5 feet, and the required tilt is 1.6 degrees, not so far off (and besides, you want to use at least f11, which will overcome slight tilt errors, and to focus about ~2/3 into subject matter to maximize the correction).
Thus, this fixed 1.2 deg tilt is very practical for landscape work (however, it is not useful for table top photography, which requires much greater tilts).
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Forum: Pentax Medium Format
05-31-2011, 04:02 AM
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The resolution of the 300/5.6 is excellent wide open, improving with little change from f8-11. The 150-300 was not as good as the 300/5.6 and definitely not as sharp as my 150/2.8. I kept the 300/5.6 but not the 150-300 zoom.
As for the 300/4 vs 300/5.6, the 300/4 is sharper at 5.6 than the 300/5.6. However, there is little difference by f8-11. The reason I passed on the f4 model is weight. The 300/5.6 is around 700 gm, the f4 twice that. When I travel, other than by car, that weight difference is equivalent to another lens, like the 120 macro or the FA 35.
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Forum: Pentax Medium Format
05-21-2011, 04:17 PM
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I had the 150-300 and found at 300 it was softer than my 300/5.6 and at 150, my 150/2.8 runs circles around it, so I did not keep it. (The 200/4 is also much sharper than the zoom at 200.)
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Forum: Pentax Medium Format
03-09-2011, 06:23 PM
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Forum: Pentax Medium Format
02-26-2011, 11:17 AM
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I just compared the P645 FA 55-110 (note: not the P67 55-100) with the P645 FA 45-85 and the P67 55 (latest) on the P645D.
At 55mm and f5.6 (wide open), the 55-110 is good in the center, but soft at the edges. At f8, the edges sharpen up and are similar to the P67 55mm at f5.6. By f11, the 55-110mm is the equal of the P67 55mm at f8, across the whole frame.
When the FA 55-110 is compared to the FA 45-85, at 55mm, the 55-110 is softer at f5.6. At f8, both lenses are good across the frame, but best at f11 for critical sharpness. Comparing these same zooms at 80mm and f8, the centers are similar, but the edges are better on the 45-85 lens. However, at f11, both are very similar across the frame.
The FA55-110 is definitely a good lens: light weight (about 500 grams) and compact, but needs to be used at f11 for best quality as f5.6 is not critically sharp, which is what using a P645D is all about.
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Forum: Pentax Medium Format
02-26-2011, 09:36 AM
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Chris,
The above comments are good, especially the idea of using a smaller lens vs the larger lens regarding weight. The 67 400mm is really good, but it is very large and heavy and manual focus.
Your Nikon D3x can tolerate a little cropping. With the AF Nikkor 300mm (either 2.8 or 4, a used model), and minimal cropping, you get a 400mm look with AF and lighter weight.
The other option I've used for special trips, is renting a lens. For a safari trip, if I used Nikon, I'd rent an AF Nikkor 500/4 ED VR. This lens would give you more reach, AF and a stabilizer. The size/wt of this lens is about the same as the 67 400mm.
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Forum: Pentax Medium Format
02-11-2011, 09:21 AM
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someone asked about the f5.6 version of the 300mm. i've posted elsewhere that it is excellent: resolution at f8 is perfect across the frame with exc contrast. at 1/2 the weight of the f4 version (in the 700 gram range), it is very nice for travel.
btw, the Mamiya f4.5 APO is about the same weight as the Pentax FA 300/4, so the 300/5.6 is decidedly the lightest 300 in MF (and needs no footplate).
the Pentax FA 150-300/5.6, is not much larger nor heavier than the 300/5.6, at a bit over 900 grams.
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Forum: Pentax Medium Format
01-30-2011, 09:15 PM
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Yes, I agree with making new lenses: it is surprising lens production was not maintained with the introduction of a new body. I can only imagine that their budget didn't allow it and they assumed existing stock and the used market would support the 645D.
Since most companies make more money off lens sales than bodies, Pentax must be eager to resume production.
Regards, Robert
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Forum: Pentax Medium Format
01-30-2011, 07:08 PM
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Hi Steve,
I'm not so certain that just because Pentax does or doesn't make lenses matters. Used lenses are used lenses and Pentax nor anyone else knows exactly what an owner has done with their lens. Maybe they dropped it. Buying used lenses has always been a crap shoot. Furthermore, we are all more picky due to viewing at 100%; we never did this with film.
The only reason Leica lenses are more uniform in terms of quality is that the tolerances are kept low, but low tolerances cost money. This is why their lenses are 3-4K each (and 10K for the latest Noctilux). This cost:quality control ratio is a fact of manufacturing anything.
If Pentax begins selling new lenses, we'll have to spend more if we want perfection. It is not just a matter of design, but keeping the tolerances during assembly and being able to adjust the tolerances to closer spec by hand after assembly.
I think it is important to have an open mind, however, that not everything Pentax made is bad. The time they spent getting the 645D to market led to a great camera. Overall, I think they've been a pioneer in making high quality lenses, and most of these lenses will work well on the 645D.
Regards, Robert
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Forum: Pentax Medium Format
01-30-2011, 06:32 PM
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I too have a late model P67 45mm that I've used on a 645D body via the Pentax adapter. However, I do NOT see any color casts as in the Steven's images. In fact, my 45mm seems quite sharp across the frame at f8. I will not hesitate to use it. There is some very mild CA noticeable in the corners, but only visible at 100%; not a serious issue to me (I've seen much worse CA on new Zeiss 24-70 zooms on the Sony A900).
My guess is that some elements are not properly centered in Steven's copy. So I would not be too quick in faulting all P67 45mm lenses. (My late model P67 55/4 is EXCEEDINGLY sharp, and also resolves very well at macro distances on the 645D body easily showing the pixel structure of my laptop's monitor at minimum focus.)
Leica M8 users had a lot of color cast issues, and there is a program called CornerFix that could correct such images. It can be used in a batch mode.
***
On a related topic:
Some people have asked for a full frame FA 35/3.5 AL image on the 645D. The attached image is a small FF JPG processed from a RAW file using Raw Developer on a Mac. The RAW file for this image can be found at (if it gets too many hits, I may delete it):
http://www.visionsurgery.net/Resources/pics/_IGP0448.DNG
It was shot on tripod, MU, wireless release, f8 at 1/250 using ISO 200. The image is sharp across the frame. (There was a slight breeze, so some branches may show some movement.) I will not bother to post other f-stops. f3.5 is softer, but who cares on a WA for landscape?
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Forum: Pentax Medium Format
01-17-2011, 02:42 PM
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I can't say if it is new firmware related, but the rear dial doesn't behave as precisely as it did before I updated. It could be a wonky knob. However, I don't think it is possible to downgrade in order to check it out.
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Forum: Pentax Medium Format
01-17-2011, 02:37 PM
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I found the FA 200/4 to be as sharp at distance as the FA 120 with even sharpness across the frame. The formula is different from the A version; the FA has 2 elements of anomalous dispersion (the FA 120 macro has 1 such element).
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Forum: Pentax Medium Format
01-08-2011, 08:15 PM
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I recently tested a Pentax A* 600/5.6 lens on the Pentax 645D. It worked well, but many images were blurred despite using MU and wireless remote (and a study tripod). I had an idea from the RRS (reallyrightstuff; http://reallyrightstuff.com/Items.aspx?code=LongLensPkgs&key=cat) catalog, where they describe a long lens support system. This provides a Y-support for the front of a lens.
However, the 600/5.6 has a very sturdy, and relatively short, front lens extension beyond the footplate. So I thought I'd flip the RRS design around and provide support for the body, as the body hanging off the lens can act as an oscillating mass.
I did a test with the single (standard) and the dual support setups. Items used: RRS TVC-24 Tripod, BH-40 head, CB-10 rail, B2-Duo clamp, MPR-ER (vertical bar), B2-mAS (clamp for MPR), B2-40LR (clamp for camera), and two B67 plates for the 645 body. In the upper right photo, you can see the CB-10 rail on the tripod head clamp; the B2-Duo clamp interfaces the CB-10 rail and the standard rail still on the lens's footplate (it has two nylon thumb screws). The B2-mAS is on the end of the CB-10 rail. Sliding up and down this clamp, is the MPR-ER with the B2-40LR on it's end. The 645D has two B67 plates, one seen on the side.
My readings on this forum seem to suggest that the 645 body is sensitive to vibrations in from 1/15 to 1/100 sec. I used 1/60 at f8 with MU and wireless release. I also observed a laser pointer on the set up. The dual support system had virtually no movement even when manually pressing the shutter release as the body and lens are rigidly connected.
The photos in the top row show the single support (a laser finder/pointer is resting on the handle) and the dual support setup. The bottom row shows 100% sized images taken at 7m with above setup. Not to be misleading, the single support setup did have the occasional sharp image; the dual setup was sharp every time.
This is not the first time someone has provided support for the body. The Manfrotto #359 system (reviewed here: 359) ties the body to the tripod. However, this design prevents easy re-positioning as the body is not fixed to different location than the lens. The RRS CB-10 based system is easy to re-position via the ball head (or a geared head).
This dual support setup would also work well with the Pentax 67 system. Due to the larger lenses, front lens support would be best, along with the longer CB-18 rail (8" longer than the CB-10). This front support would require adding parts at the lens end of the CB-18 rail: one CB-EC connector, one CB-YS and another B2-mAS clamp.
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Forum: Pentax Medium Format
01-05-2011, 06:26 PM
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Forum: Pentax Medium Format
01-02-2011, 01:24 PM
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I agree with Royce.
The only manual focus lens I have for the 645D is the 600/5.6. It is relatively straight forward to see when it is in or out of focus. It certainly helps to have the finder in focus and proper correction in your glasses if you wear them. (It is surprising how many people don't realize they are going around with minor focusing errors like uncorrected astigmatism and therefore cannot distinguish fine details except on an enlarged computer screen.)
I've used the 150/2.8 and the 75/2.8 in manual focus mode and they work just fine too. The AF and my manual adjustments agree.
While admittedly, a lack of a center microprism, or other focusing aid, makes it more difficult to judge focus because the end point is more subtle, I wonder if a contributing problem may working too fast and thereby missing the plane of focus. Manual focus requires more accuracy than AF from the user.
To further compound the problem (but still related to accuracy) is the larger format itself: the DOF is less with MF and LF. When focusing the 600/5.6 lens on the 645D at 5m (it's closest focusing distance), the DOF is less than 1/4 inch. Certainly the DOF is greater for wider lenses, but they still have less DOF than their 35mm counterparts.
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Forum: Pentax Medium Format
01-01-2011, 05:41 PM
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One thing that's struck me in reading reviews of the new 55/2.8 AL, is that they sound just about like the reviews for the Pentax 55/1.4 DA* for the K-series APS bodies: center is very sharp but edges are soft.
I've not tried to track down the schematics for the two (AL is 9-7, the DA* is 9-8 groups), but maybe they share similar design goals. I can understand for the APS lens since it behaves like a portrait lens and one could argue the edges can go soft, but for a modest WA on 645, this would seems like an odd choice.
here is one detailed review of the DA*; kinda sounds like Lloyd's review:
[url=http://www.lenstip.com/163.4-Lens_review-Pentax_smc_DA*_55_mm_f_1.4_SDM_Image_resolution.html]Pentax smc DA* 55 mm f/1.4 SDM review - Image resolution - Lenstip.com[/url
I need to add, however, that somewhere I read that Lloyd and others had not found any Pentax ads using the new 55mm. This may be true outside of Japan, but not true in Japan. While in Japan a couple of months ago, I bought a copy (Japanese text only) of Pentax's "645D Official Book". It has numerous examples using the 55mm and all of them look outstanding.
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Forum: Pentax Medium Format
01-01-2011, 04:07 PM
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Today, I tested on the 645D the following FA lenses: the 35-AL, 75 and 45-85. All lenses seemed equally sharp from edge to edge.
The 75 is excellent. A tad soft at f2.8 with a flared look, but sharpened nicely by f4. It was very, very nice at f5.6 with high contrast. So far all lenses look great at f5.6 (and f8 and f11; I cannot see much difference at f11, including diffraction, just greater DOF).
The 35 was interesting. It was my first 645 lens to measure that had the plane of focus off. It back-focused, requiring +6 to fix. But as I re-tested to trim in the focus adjust, and examined all the f-stops, I found something odd. The 35 still back-focused at f3.5-f4, despite having adjusted it for accurate AF at f5.6. (The AF was consistent from f5.6-f11). It would appear to be a shift in plane of focus with stopping down. The target was about 3 m away. Since I don't shoot wide angles open, it is not much of an issue for me, but thought i'd pass it along.
The 45-85 is nice. It did require +1 in focus adjust, but aside from that, it is very good. The only lens in the same range I have for comparison is the 75/2.8. At f5.6, the 75/2.8 is superior. So while the zoom is good, it is not as good as a prime, at least my copy. It also seemed to have a tendency to flare when used wide open (like the 600/5.6 did wide open). f5.6 is where I'll shoot it as the contrast is better.
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Forum: Pentax Medium Format
01-01-2011, 12:27 AM
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The past couple of days, I've had a chance to test on the 645D the following FA lenses: 120/4, 150/2.8, 200/4, 300/5.6 and A-600/5.6. I have yet to test the FA-35 and 75.
All lenses were spot-on with AF, as was the 600 with AF-confirmation (visually, it was not difficult to focus). All of the lenses were sharp wide open, but improved closing down 1 stop. I had no issues with variation in side to side sharpness; at least, after stopping down 1 stop.
The 600/5.6 was much better at f8 with improved contrast. It seems to have a tendency to flare a bit at f5.6 and have lower overall contrast.
I particularly like the 300/5.6 for traveling as it is 1/2 the weight of the f4 version. While f5.6 was sharp, f8 seemed optimum with greater contrast.
In terms of sharpness at f5.6, the 120 and 200 seemed best, closely followed by the 150 and then the 300.
Overall, I am very, very pleased with the Pentax 645D system.
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Forum: Pentax Medium Format
12-30-2010, 09:47 PM
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Hi Tim,
No I do realize that 1° can be annoying; I've had to correct these amounts in PS before (even 0.5° is noticeable). For stitching, having the body level is important (which is why most built-in bubble levels seem next to useless to me).
But I doubt that the built-in level can be much better than about ±0.5°.
The one solution, short of having Pentax fiddle with it, is simply to know, as I now do for my 645D, that 1 or 2 yellow marks to left, with the green for fore/aft, is perfectly level in landscape position. I just need to remember (or write down) this adjustment.
If we do this 'self-calibration' and remember to adjust for it, we'll know the camera is level. I would rather do this than ship the body off.
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Forum: Pentax Medium Format
12-30-2010, 10:03 AM
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I have a few bubble and electronic levels that are very, very accurate and used these for reference, not the horizon. I did the measurements in my house, so I did not look to see effects of temperature. It is possible that extreme cold/heat may affect readings. I used RRS brackets for holding the cameras to the tripod and use a leveling base for adjusting the tilts.
My 645D is spot on for left/right tilt when in portrait position and off by 1° in landscape. For tilt down and back (fore/aft), the 645D was spot on in portrait and landscape positions.
The yellow markings on the 645D indicate in landscape it was off by 2°, but once I corrected so only green showed, the actual correction applied was 1°. This probably means the displayed markings have their own tolerance of ± 0.5°.
I similarly checked my K5. Fore/aft tilt is spot on in all positions, but left/right is off 1° in landscape, and 1.5° in portrait.
My guess is that with the display they've chosen (1° increments), their set accuracy is going to be ± 1° if one takes into account the actual sensor tolerance and the display increments. Since most people have used bubble levels, this is still better than what we've been used to using.
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Forum: Pentax Medium Format
12-28-2010, 11:08 AM
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Nick,
It would be nice if the 645D would allow a "UniWB" mode. I've not been able to easily do this with Pentax (as can be done with Canon or Sony). If Pentax could provide a UniWB mode through software, it would be a unique tool for photographers.
-Robert
_____
Uni-White Balance (UniWB) background:
UniWB displays a histogram of the RAW data, not the usual histogram of the processed JPG. Since there are 2 green pixels for each red and blue in a Bayer sensor, the UniWB mode on a Canon/Sony camera appears green, but allows one to truly ETTR, better utilizing the sensor to maximize the S/N.
If one does an ETTR now with the JPG histogram, one is not actually ETTR for the sensor, but simply ETTR for only the red channel (and sometimes the blue). This leaves the green underexposed and increases noise. Thus, ETTR on virtually all digital cameras is misleading.
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Forum: Pentax Medium Format
12-28-2010, 01:00 AM
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Very nice! I like it too.
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Forum: Pentax Medium Format
12-27-2010, 08:24 PM
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MikeSeb,
I'd have to agree with the other posters, I think Pentax has a slight bias to underexposure. I too have seen it with Sony A900 and now with my 645D images. But personally, I would rather be on the under exposed side than over.
Of course, some scenes with great contrast can fool any metering system, and would probably require bracketing anyhow to get the whole thing properly recorded (making a under exposure moot as you'll have to make many exposures anyway).
I look at the peculiarities of any camera as simply one we, as you say, 'have to learn to deal with'. (And no matter what, much better than the film days when we'd only figure out a mistake days later).
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