Pentax FA 645 Lenses
For the last 12+ months, I have been working intensely with multiple samples of Pentaxís single focal length FA autofocus lenses designed primarily and initially for their 645 film system, by employing their use on their new Pentax 645D Digital MF body. A wide variety of lens samples was primarily obtained courtesy of long time associations with MF 645 and 67 Pentax photographers, who kindly lent samples of their lenses for this project as well as my own purchases of lenses.
Iíve also had the opportunity to work with and test a small sample of their FA zooms.
Much has been written about the new Pentax 645D and by accounts it is extremely competent performer, a superb value and has shown to consistently deliver professional quality MF files. It is also an excellent handling camera with a great feature set. If there are limiting factors in this first offering by Pentax in the Digital MF marketing place, it was initially thought their film era developed line of medium format lenses might not be up to the task. Even by Pentaxís own accounts, only certain samples of some of their 645 lenses would perform well enough for use on the 645D at a high level. Prior to investing time and money into the system, I set out to determine just how extensive these concerns were. Employing both methodical testing of multiple samples of each lens as well as paying careful attention to shooting techniques, I wondered if I would be able to come up with a set of suitable excellent performing lenses in a variety of focal lengths necessary for my own particular shooting needs and whether it would be a too much of a daunting task or not. Happily I can report itís not, although very careful consideration to certain factors is necessary to achieve this goal. I limited myself primarily to FA autofocus 645 lenses for this first round of testing and although the numbers of samples of each focal length certainly doesnít qualify for statistical significance, hopefully it does show that with certain lenses, careful selection, testing and setting of AF fine tune in the 645D body, can be very important. I suspect unlike most MF users, especially landscape photographers, I often have the need and desire to use lenses at more open apertures, therefore necessitating my testing of these lenses and to first determine the best AF fine tune adjustment for each individual sample before additional testing and consideration was performed.
Determining the optimum AF fine tune setting did not always follow the convention of AF fine tune setting at minimum focusing distance and then allowing the increased depth of field as subject distance increased, to cover for any slight offset. Often times a subject distance at mid range or even infinity proved to be the best AF fine tune setting for a wide variety of applications. This was one of the most time consuming first steps when testing any lens and often a compromise subject distance was picked to determine the AF fine tuning setting, especially if the lens was to be used for a variety of camera to subject distances. If a lens was strictly going to be used for landscapes at infinity, then sharpness across the frame might be enhanced if AF fine tune setting was determined by testing at infinity. Spherical curvature observed in some lenses made this a necessity.
Iíll also mention that all test files were examined at actual pixels (100%), so that many of the observations or issues presented in this report may not be evident if one is only concerned with looking at screen resolutions or slight magnification. Output to large format print was the primary goal, so observing at 100% became a necessity.
Each lens was tested two ways:
1. Camera/lens squared up to a frame filling brick wall and tested at minimum focus distance, mid-distance and the longest possible subject distance that allowed the frame to be filled with this test target. Lens was tested at all f-stops.
2. Camera/lens was tested in real world shooting with a wide variety of subjects (at a variety of angles to the subject). Three camera to subject distances were employedÖminimum focus, mid-distance and infinity and at all f-stops. The one exception was the FA 120mm f4 macro, which was tested in a wider variety of subject to camera distances, due to its increased focusing range.
The following observations are not a definitive statement of the optical potential of each focal length lens, as there are far too many samples of each lens produced over the years. What is apparent is often a moderately wide variability between samples when used at apertures wider than normally associated for landscape. One possible explanation of this performance variability is that these lenses were all produced (except for the new WR 55 f2.8) during the film era and although most might have passed quality control for optical performance on Pentax 645 film bodies, some samples fall short when confronted with the demands of a digital sensor. Lenses passing QC might have done so on either side (+/-) of a theoretical perfect ďnullĒ and therefore the further they are removed from perfect adjustment, the more issues they might present to the sensor. This imperfection is not only is restricted to front/back focus, which the 645D body can often compensate for (with AF fine tuning), but optical alignment of elements/grouping which determine lens performance when properly focused. This often encompasses skewing of elements, which may lead to asymmetry, which is often observed as a blurring of one or more sides or corners. Rough handling of used lenses was often thrown out as a possible cause of poor performance as most lenses I tested were originally purchased new lenses by the respective photographers and were handled with great care during the course of their use. The equivalent 35mm focal length of each lens when used with the 645D is noted in parenthesis ď( )Ē next to the actual focal length of each lens.
1. FA 35mm f3.5 (28mm) . This very popular lens is an excellent performer under most but not all shooting conditions. Itís performance varies greatly depending on subject distance, f-stop employed and whether the subject is greatly affected by the extensive spherical curvature this lens exhibits primarily at long camera to subject distances. I tested out more samples of this lens (greater than 10), than any other FA lens. The spherical curvature appears small at relatively short distances but quickly grows as the focusing distance increases. At typical landscape distances, many samples display enough spherical curvature so that edges/corners are softer than the central portion of the frame. If one though looks though at the edges/corners (such as the lower right and left ones) that are in the foreground of an infinity focused landscape, these corners are often sharp compared to the upper right and left corners at infinity. This is a result of this spherical curvature. Camera/lens angle and distance to the subject can also greatly influence this. Some barrel distortion is evident with this lens, but nothing thatís not easily correctable in post processing.
** One sometime strange observation Iíve observed with this lens is what Iíll refer to as a ďblur zoneĒ. Iíve noticed it in almost all samples (although not in all images with a well defined consistency) an area of the image where all detail in the subject is slightly blurred. Everything above/below and around that zone is sharp and itís certainly not due to movement of subject (unless a small area of an entire brick wall moved!). Iíve seen this at a wide variety of focus distances. Itís more prevalent at the wider apertures and decreases to an extent when stopped down. It comes and goes and I yet donít have a handle on a well defined set of parameters to ensure 100% of its appearance. Recently some other FA 35mm f3.5 lens shooters also independently noted this strange anomaly as well as one individual with their MF 35mm A 645 lens. If I had to describe it, it looks like a small group of tree leaves in an entire image of trees together with their leaves, had moved in the wind during exposure....while the rest of the entire mass of trees with their leaves contained in the rest of the image are perfectly sharp. Could it be due to the slightly uneven pouring of the resin used to make the aspherical containing lens element? Purely conjecture at this point and its rarely observed.
Conclusion: A very fine lens, sharp but with somewhat better performance at close and mid-range. Still good for landscapes but depending on sample, edges/sides may be ďmore or less sharpĒ at infinity. Sweet spot on the 645D is between f11/f13. The lens really picks up in resolution at around f6.7, for those who desire to shoot at a wider apertures. CA is evident in brightly lit reflective situations, but itís fairly well controlled and doesnít present an issue when the lens is well stopped down. Sample to sample consistency is fair at best and there were notable differences. Getting the 645D AF fine tuning right with this lens is critical and makes a big difference in performance. AF fine tune settings varied greatly between different samples of this lens, with some of the widest variation in settings among FA lenses. Lens AF fine tune settings covered the range of +10 to -8. The AF fine tune setting also has a great effect on the presentation of spherical curvature with this lens and exactly how close or far back it presents itself in an image. A lengthy article would be required to describe the why and how the 645D AF fine tuning affects this, relative to keeping infinity sharpness respectable at a chosen setting. The MF 35mm f3.5 645 lens is mentioned by some to have slightly improved edge/corner performance than the FA version but with a notable increase of CA.
2. FA 45mm f2.8 lens (35mm). Although a fast lens with a moderately respectful reputation with film users, I was previously made aware of itís less than stellar performance on the 645D. I only tested two samples and both performed similarly. The lens I suspect would not be favored by most critical users. Its central sharpness becomes respectable by f11/13 but the sides and corners are fairly soft.
Conclusion: Itís not one of the group of lenses I would personally recommend when shooting with the 645D. . I didnít specifically test for CA and the AF fine tune setting between these two lenses appeared similar.
3. FA WR 55 f2./8 (43mm) This newly released lens (at the same time as the 645D) has been much maligned, and in my opinion, often by word of mouth from those that havenít even shot with it or compared with lenses of similar focal length. Like the FA 35mm f3.5, Iíd recommend its use more for close and mid-distance or at landscape infinity distances, where ultimate edge/corner sharpness that matches central resolution isnít required. Contrast, possibly by design seems to be lower than the average FA lenses made in the film era. This too contributes to images that donít instantly pop out at the viewer. Lens can be used even wide open (with some edge/corner softness and small loss of central resolution) and of course is weather resistant like the 645D body, making an ideal pair, when the weather turns bad. Stopping down to its sweet spot of around f11 still presents edge/corner softness with some subjects in long distance shots. Whether this is important is up to how the lens is used or the particular subject matter. I tested 3 samples of this lens, and all were consistent with one another, including AF fine tune settings that only varied slightly and not far from a neutral ď0Ē setting.
Conclusion: Overall itís a good-to very good lens as opposed to a maybe a great one but when considering itís WR (which does instill confidence when using it along with the 645D in the rain/snow), results in a ďplusĒ. It is also a quiet focusing lens for those situations where the whirling sound of a screw driven AF lens would be obtrusive. CA was evident but in very measure amounts and stopping down reduced what was evident. By stopping down the lens with each f-stop by starting at f2.8, presents an image that picks up resolution across the frame in a very even and predictable way.
4. FA 75mm f2.8 (60mm) This is the ďLittle Engine That CouldĒ. Very small and light and feels cheaply made, this lens surprises all who try it on their 645D. Unlike most FA lenses which have a simple push-pull focus clutch mechanism to engage and disengage AF, this one has a little switch on the side which isnít as convenient. The lens was often the kit lens supplied with the Pentax 645 FA film bodies. At f2.8 image often are jittery and soft and in most cases not ideal. At f4 in some tested samples, things pick up and it can be used at this aperture in a pinch. Itís at f5.6 where this lens starts to shine. Lovely sharp images with good edge/corner performance at this f-stop and beyond with nice OOF rendition. Sweet spot at f11/13.
Conclusion: Often found at remarkably good prices, this lens is what I would often suggest to a 645D users, especially at its price point and its convenient small size. One thing that does sometimes present an issue is its very high levels of CA under certain lighting situations. Some of the highest amounts of CA Iíve seen in a FA 645 lens and observed it in all 4 samples I tested. It can be dealt with in post processing to a good degree, or by stopping down to f8/11 where little evidence is seen. AF fine tune settings were all biased towards the ď-ď directions, just slightly off from ď0Ē. A gem of a lens for its price/performance although there is some performance variation from sample to sample.
5. FA 120 f4 macro (96mm) If ever there was a lens to begin an adventure with for a 645D users, this is it! To start with, less variability in sample to sample performance in extensive testing, than any other lens in the FA line-up. Not only that, but itís the only FA lens where each one required no 645D AF fine tuning. This might be due to the precision and adjustment a macro lens requires prior to leaving the factory, even in the film days, since performance on both the close focusing range as well as infinity is desired. Lens is heavy and its weight surprises some. Itís well built and has a focus limiter switch which truly helps in focus hunting. Sharp images with good contrast are obtained edge to edge from macro range to infinity. A very consistent performer (I tested 4 samples) and although there may be a lens or two that might better it in one parameter or another, itís hard to beat its overall performance. Although f4 is good, it gets even better upon stopping down. It also able to get down to 1:1 macro. One glaring area where it falls short is its OOF bokeh in normal focusing range. Itís not terrible, but depending on background subject and lighting itís not the most attractive and for portrait work would not be my 1st choice in FA lenses.
Conclusion: Most everyone agrees, this lens can always be counted on to be a superb consistent performer in almost all areas except possibly portrait work due to its somewhat unattractive bokeh at normal focusing distances. Even there one can make due. I am just beginning a project in using this lens in its macro range and so far performance is impressive. Shooting at f4 for general (non macro) subjects is very good but the lens like the WR 55 f2.8 lens gets progressively better when stopped down. Sweet spot seems to be around f11/13 although for general hand held use, f8 does well. CA is fairly well controlled at f4. A great lens with almost no reservations.
6. FA 150mm f2.8 (120mm) The very first time I picked up one of these lenses, I though someone was playing a joke and removed some of the internal glass elements. After physically picking up the FA 120mm f4 macro, this lens seemed light, too light! A very pleasant surprise and knowing it was a f2.8 lens (as opposed to the 120mm f4 macroís f4), I was not prepared for this weight reduction. Unfortunately all was not good initially. The 1st sample was mediocre at best until f5.6 as was the 2nd sample. The 3rd sample was decent in the center from f2.8 but the edges/corners were terrible until f8. The 4th and 5th samples were better with the better of the two what I was hoping for. The best sample was reasonably sharp at f2.8 centrally, just about perfect for portrait work which its f2.8 aperture is ideal. At f4 it picks up some resolution, and was useful for most general hand held purposes. Edges and corners at f2.8 and f4 are respectable but do lag behind the center. At f5.6 the lens is in its element, good all around and this continues at f8/f11. Itís OOF attractive bokeh is far superior with this lens than the FA120mm f4 macro and along with its performance at the more open apertures, is an ideal portrait lens which one presumes it was intended for. Yet it does well as a nice relatively fast all around lens which due to speed, can be used hand held. Whether testing more samples will yield this wild variability, I cannot say, but it was worth testing these samples to find one that did not disappoint. My impression is its contrast is lower than the FA 120mm f4 macroÖwith a more gentle and delicate presentation. Again possibly due to itís roots as a portrait lens.
Conclusion: Light for its focal length and speed, a lovely portrait lens and all around performer. It does benefit from stopping down somewhat. Good OOF bokeh and sharpness across most of the frame is achieved by f8 although may fall slightly short of the best of them. Itís a lens that a bit more delicate in itís image presentation and may not wow those looking for a higher contrast, slightly sharper lens. Each type of lens has its place and will greatly depend on subject and lighting. The main issue is finding a sample that performed as described. AF fine tuning required a +6 on the best sample with most others also on the + side of the scale. CA is evident with bright contrasty lighting but well within controllable amounts, especially after stopping down a stop or two.
7. FA 200 f4 (160mm) Red flags were raised when I tested my first 4 samples. First three were simply horrible and fourth wasnít too much better and yet others that I asked, demonstrated fine performance with theirs (on their 645D). Images were jittery, blurred, and soft up to f7.1 Even the screen resolution shots didnít look particularly sharp as I figured this was just one of those lenses (the FA 200 f4) that doesnít interface well with the 645D. These samples were barely acceptable at f8 and decent by f11. If someone had one of these lenses in their possession and only shot at f11/13, they might or might not noticed decreased performance when pitted against a ďgoodĒ sample which I eventually came across. I even went back and tried one of these poor performing lenses on a 645 film body and the small prints looked good. I then used a scan and printed a little larger. Images were still fairly sharp and acceptable. After some time I was lucky enough to have the opportunity to test out two more samples. Both of these to my relief performed well by f5.6 and decently at f4. The lens was also of lower contrast, similar to that of the FA 150mm f2.8. At f8 the lens looked sharp but lacked bite compared with the best of them. The sweet spot was closer to f13 than f11. Edge corner performance by f9.5 was very good, but still fell short of the center. The FA 200 lens is relatively compact and is the longest focal length FA 645 telephoto thatís compact enough to take in a small bag. Next longer lens in line is the FA 300 f4, which makes a giant leap in size and weight as compared to the FA 200 f4.
Conclusion: A good sharp lens, especially when stopped down, but the images it produces lacked excitement, for lack of a better description. Possibly ďneutralĒ is a better word to describe how it draws an imageÖcompetent but not exceptional with lower micro contrast than some other FA lenses. Itís relatively compact size and weight, make for a good travel telephoto, when more reach is required. CA is a better than average and so far hasnít been evident in any meaningful way.
8. FA 300 f4 (240mm) A quite renowned lens thatís often mentioned as having excellent performance characteristics for a long MF telephoto. Size and weight is considerable if compared to most other FA telephotos. It has a built in rotatable tripod mount, but some flex and camera/lens vibration is quite evident and often spoils the shot. Optical performance is exceptionally good, even at f4 but improvement can be readily seen by stopping down a stop or more. Lens has excellent contrast and micro contrast and more than excellent sharpness by f5.6. Even with mirror lock-up, a stable tripod set-up and carefully selection of shutter speed, image robbing vibration was often evident. Various techniques were employed to reduce this with a degree of success. Although the lens is sharp, one should not expect the extreme sharpness and acuity of a Nikon 300mm f4 or 300 f2.8 SLR lens when itís shot wide open at f4. Itís just different yet never less impressive in its own way.
Conclusion: If long range shooting is in ones plans, then this often expensive optic might just be the ticket to achieving ones goals. I didnít specifically test for CA and AF fine tuning on the three samples I tested two were slightly offset from ď0Ē and a third was +8/+9. This last sample though proved to be the best optically and most impressive. Other than size and weight and sometimes cost, this relatively fast telephoto can be a valuable assets if one desires a longer range telephoto that quite capable in the field. I have just begun testing the Pentax 1.4x converter with this lens and hopefully will report back my findings.
9. FA 300 f5.6 (240mm) Based on the testing a single sample, this lens is lighter and more compact than its bigger brother, the FA 300 f4 with somewhat similar performance to the FA 300 f4 when stopped down. Contrast though is somewhat lower than the FA 300 f4 giving the impression of decreased sharpness when comparing the two. This lens comes into its own at just beyond f8. Sharpness is good, but I honestly canít say whether it matches the FA 300 f4, until further testing in comparing the two. Conclusion: More reasonably priced than the FA 300 f4 and lighter in weight, this lens may be a more sensible approach for those than donít use a long focal length lens in this range very often, especially when shooting MF. I didnít test for CA and AF fine tune setting was +1.
10. FA 400 f5.6 (320mm). This lens by appearance looks like the big brother to the FA 300 f4. Larger, longer and heavier, this lens needs to have a specific purpose in order to find its way into many MF shooters bags. With all the attention given to the ďgold ringedĒ Pentax FA 300 f4 EDIF lens, I initially didnít have high expectations for the FA 400, especially that Pentaxís FA 400 f5.6 lens in 35mm format, was a disappointment from my extensive use of that lens. To much surprise, this lens optical performance was acceptably good at f5.6 but stopping down to f8 and beyond put this lensís performance close to the FA 300 f4. The look of this lensís images closely resembled the FA 300 f4 with somewhat lower micro contrast. It has fairly good resolution on axis and very good contrast at all apertures. Although it too has a built in rotatable tripod mount, it also suffers from the same image robbing properties due to vibration, much like the FA 300 f4 . Both these lenses benefit from some type of long lens support. Mirror slap in the 645D is well dampened and doesnít seem to be the primary contributor to these issues. Iím currently looking into what steps and techniques will help.
Conclusion: A very fine relatively long telephoto although fairly big and heavy. Sharpness by f8 and especially by f9.5, should give those trying to extend the reach of their MF shooting, something good to work withÖ.especially if they keep in mind the requirement of employing exceptionally good long lens techniques. Both samples I tested also required slight offset from zero in selecting best AF fine tune settings. I didnít specifically test for CA. I plan some additional tests employing the 1.4x converter.
11. FA 45-85 f4.5 zoom (36-68mm) . Although zoom lenses are often compromises when compared to their single focal length bretheran, this particular lens will certainly exceed the expectations of most. Sharp throughout most of its focal length range, itís good handling and design, although somewhat heavy, makes it a joy to work with. Its range is sufficient to cover general purpose shooting or for those times when only a single walk around lens is desired. At its wide end of 45mm sharpness is very evident, even wide open and improves upon stopping down. The same holds true for a zoom setting of 65mm. At both these focal lengths, sharpness extends well into the edges/corners and performance can be considered exceptional for a MF zoom. At 85mm things begin to change. Some spherical curvature sets in although in both samples, with optical alignment of elements (or group of elements) seemed to be slightly off, relegating one side/corner or the other to some blur within the focusing plane on one of the tested samples. Central sharpness is good, especially upon stopping down to f6.7 and beyond, but edge/corner sharpness lags behind, especially on the side where asymmetry is noticed. It doesnít quite ever catch up with center sharpness in the three samples I tested. The sweet spot for this lens, especially at 85mm would be f11/13, although I wouldnít hesitate opening up if necessary when shooting at 45-65mm. Some barrel distortion was evident, but relatively small and easy to deal with.
Conclusion: Another very fine FA lens and one in which has grown on me, simply for itís acuity at 45-65mm and use of its focal length range. Itís not a complete substitute for single focal length lenses in its range, but can often compete for the job in many situations. All samples tested required significant AF fine tuning adjustment of +5 and +6 respectively. I havenít completed testing of these lenses nor have noticed any serious issues with CA while shooting.
12. FA 80-160 f4.5 (64-128mm) . Iíve only worked with a single sample of this lens, so I hesitate to make any sort of pronouncement of its performance, especially related to other samplesÖ.although I have conferred with a few others who use this lens, when I noticed a slight bit of disappointing performance at its longer end. Whereas the FA 45-85 zoom at itís 85mm end shows its relative weakness, the FA 80-160mm seems to compensate for it (at 80mm) when these lenses are used as a sort of matching pair. It almost seems thatís what Pentax intended. Approaching 160mm, the lens sample I tested grew quite soft and only upon stopping down to f11/f13, did I feel it had sufficient resolution necessary for my own expectations.
Conclusion: A handy focal length that may or may not be somewhat disappointing in optical performance. I simply need to test additional samples of this lens to make any definitive conclusion but have spoken to others who have used this lens on the 645D and although opinions varied, the majority felt it was simply good at its wider end but not the best of lenses. A few felt otherwise.
13. A* 600 f5.6 (480mm). Recently Iíve started to put the Manual Focus (only) Pentax A* 600 f5.6 lens through its paces. It has no auto focus counterpart. A lens of modern design with a superb reputation among Pentax 645 users, Iím eager to see how it performs in a wide variety of situations, with and without the high quality Pentax 1.4x 645 teleconverter, which is often used with this lens. I hope to report on my findings at a later date.
Just to note: I hope to eventually test out the new Pentax D FA 25mm f4 645 lens with the 645D sometime in the future (depending on availability). The few preliminary reports and images posted so far seem to indicate an exceptionally good lens, especially when stopped down. Center resolution appears somewhat ahead of corners. Unfortunately evidence of moderately high CA at the more open apertures appears to be clearly evident. Again this assessment was made by the few who were able to test out this lens on a 645D.