michael_kuhne

<p>David, did I not just say basically the same thing?? What did I write in the last paragraph above regarding using a 135mm lens on both FF and APS-c bodies? "If one has a 24mp FF (Full Frame) body, shooting with a 135mm f/2.8 lens, then cropping to obtain an image comparable to that of the APS-c body using the same lens...." </p> <p>Then you write saying "There is no difference between cropping a full-frame image to the size of a crop sensor size than taking the same picture with a crop sensor and the same lens." I wrote the same thing, except for using other wording: "cropping to obtain a comparable image to that of the APS-c body using the same lens..."</p> <p>The caveats I brought up were regarding the pixel loss due to the cropping, in addition to carrying larger, heavier, more expensive equipment.</p>

<p>William, you are right- what I meant to say is the FF image would have LESS DOF. Glad you spotted that. Yes, you are absolutely right. Subject distance relating to focal length and perspective are very important considerations. The distance of the background behind the subject is also important in determining what aperture is needed to blur the background.</p> <p>David, apparently you are not understanding what I said. Of course, technically, a 500mm lens is a 500mm lens regardless of its being on a FF or APS-c body. But the practical result IS different.</p> <p>Of course, technically, the APS-c image represents a cropped cut-out of the concurrent FF image. But that is an important difference.</p> <p>I mentioned pixel density because someone brought up throwing out pixels. But here goes. Pixel density, of course, does not "change" the focal length of a lens. But differences in pixel density have a lot to do with cropping and the resulting image. I see that you know that higher pixel density means higher resolution, which can show more detail on a subject. Good thing to know. But at the same time, this has a LOT to do with FF vs. crop sensors.</p> <p>Carrying around a 135mm f/2.8 lens on an APS-c body, in real-world use, for all practical purposes is akin to carrying around pre-cropped images similar to those taken with a 200mm f/2.8 lens on a FF body. In using the APS-c setup, one is saving weight, size, and expense compared to the FF setup for getting similar results.</p> <p>24mp APS-c sensors and 24mp FF sensors do not have the same pixel density, because the 24mp's of the FF sensor are spread over a larger area. The 24mp's of the APS-c image are crammed into a smaller area, having greater density compared to the same amount of pixels in a FF image. Even when evaluating lens and camera testing, where resolution is given in lines of resolution, it is important to take this difference into consideration, because results are given in lines per picture height. The numbers like 3,000 lines look more impressive in a test using a FF model compared to less lines for an APS-c model, but the frame height with FF is 24mm, so the lines given are spread over a greater area compared to the 16mm frame height of APS-c models.<em><br /></em><br /> <br /> One has to have a FF body with a sensor of more than 24mp (I am not sure how much more) to equal the pixel density of the APS-c body having a 24mp sensor. But even then the weight and expense is still an issue. If one has a 24mp FF body, shooting with a 135mm f2.8 lens, then cropping to obtain a framed image comparable to that of the APS-c body using the same lens, pixels must be discarded in the process. No longer will it be a 24mp image, while that taken with the APS-c setup will remain a 24mp image. In only one respect could the FF setup prove to offer an advantage when shooting telephoto, as we are speaking of- that is noise occurring when facing low-light or higher ISO use, where FF sensors exhibit superior performance. But when speaking of wide-angle to normal focal lengths, the advantages are pretty much all for the FF format.</p> <p> </p>

<p>Interesting thread. Of course, an APS-c image does represent more of a blowup under the same circumstances. It is essentially like using a longer tele lens, and the rule for tele vs shutter speed must be adjusted, even though it can be lower than standard when SR is employed. As to throwing out pixels, the fact that a 24mp FF model has less pixel density than does a 24mp APS-c model might also be considered.</p> <p>So after addressing the camera/lens aspects, as others have stated, the main issue is that here a live subject creates a separate set of parameters compared to still subjects. Live subjects invariably require higher shutter speeds to assure sharp results. At least 1/125 sec. and better at 1/250 for a subject holding "still". Portraits are often shot at larger apertures to defocus and blur background to make the subject stand out from the background. The last example shot would have been better at a larger aperture instead of f/10, especially since the background contains nothing of interest to include in the scene, so would be better defocused with the subject standing out from it. The larger aperture would also allow a faster shutter speed at the same ISO.</p> <p>Using a large aperture can also be overdone. In the case of a lens having f/1.4, using maximum aperture presents its own problems: The lens will not be all that sharp at such a wide aperture. At a portrait distance, focus would become extremely critical, especially with a live subject, since DOF is extremely shallow. The eye may be in focus, while the ear is not. Also, with the slightest movement, the subject could move out of focus between the time focus is locked and the shutter is tripped. f/2.8 would be better depending on the focal length used and the subject distance. DOF would be shallower at 200mm, but less so at 70mm. 70mm would be better for portrait because subject's features would be more natural, less flattened than at 200mm.</p> <p>I am not sure about the multiplying of APS-c images to a smaller aperture to get the same DOF as a FF image. I may be misinformed, but my impression has been that APS-c models tend to have MORE DOF under the same conditions, while a FF model has more capability to reduce DOF. That is to say, the APS-c body with a lens of 135mm @ f/2.8 would produce about the same image as a FF body with a lens of 200mm@ f/2.8 but the FF model would have greater DOF. Or, when getting a portrait shot, the FF model could obtain more background blur with a lens using the same aperture and image framing.</p>

<p>Very good! This is the kind of information I was hoping for- a differentiation from the original Pentax SDM AF motor. Andrew is essentially also right, the rebadging includes the Tamron motor. Thanks, Alexandru, for such insightful and very detailed information.</p>

<p>I figured Pentax switched to DC because of past reliability problems with at least some SDM models. Maybe you are onto something, Andrew, the 3rd party AF system is simply rebadged as "SDM" since it is not DC. </p>

<p>Anyone else notice the new lenses that are apparently rebadged (very good) lenses from Tamron have been outfitted with SDM AF motors? These are the D-FA 15-30mm f/2.8, D-FA 24-70mm f/2.8, and DA 18-270mm f/3.5-6.3, all SDM. Those newly issued which originate from Pentax, like the D-FA 70-200mm f/2.8, the DA 16-85mm f/3.5-5.6, the D-FA 28-105mm f/3.5-5.6, the DA 20-40mm f/2.8-4 Limited, and still others of recent Pentax origin, have DC AF motors.</p>

<p>Whoops! The Imaging Resource field test of the K-1 has come in. I just read it. Very interesting, and comprehensive. They have found the AF to be an improvement over the K-3 in both field and lab testing. But they note for action shots where burst rate is important, the K-3 is better. I also have to believe that very expensive pro-style Canon and Nikon designs, where fast sports action is a major objective, the lesser MP values used are there as a compromise to allow greater write time, buffer clearing, burst rate, and buffer capacity. Their AF speed may also benefit.</p> <p>I partially agree with the reviewer's reservations regarding the smaller top LCD vs. the new control knob, and the new style of back LCD articulation.</p> <p>I do not agree with the reviewer, who thinks the crop mode in the VF should black out the outer full frame image instead of a line. Having the line allows for seeing if one would rather go to a full frame lens, or going to full frame operation while accepting any disadvantages imposed by so using a DA lens, and compensating in a post process. </p> <p>Overall, the K-1 got a very high recommendation.</p> <p> </p>

<p>BTW, the test for noise control Pop Photography used was RAW conversion default setting as supplied with the camera. On the other hand, in the case of JPEGs the camera automatically will apply more noise suppression as ISO is increased. I saw the results of that with the shots done in Imaging Resource's comparometer. Both low noise and retention of detail were very impressive. Or, as with RAW, you can turn noise suppression off and take care of it post process with a program of your choosing. So far this camera is proving itself in real world use, for its excellent image quality, features, and flexibility.</p>

<p>Matt, yours is the kind of user reports I was thinking of. Although not of fast action such as sports or fast moving animals, it indicates competence, and your comparison with your K-3 is important. </p> <p>I have shot fast-action roller blade hockey with my K200D, K20D, and K5IIs with very good success, not that some Nikon models could not have served even better.</p> <p>If the AF of the K-1 is shown indeed to be at least as good as, or an improvement over the K-3. and its JPEG sharpening has a good range of adjustability upwards, it should be a total winner in my book. Pop Photo magazine just released their test of the K-1 in the July/August issue. They found its AF to be "fast" but not quite as fast as the competition. They found noise /ISO levels to be low through ISO 400 and good through ISO 1600, so its IQ got an excellent rating only through ISO 400. But they acknowledged Pentax's approach for very conservative default noise suppression, which allows the user latitude to increase as desired. The result of this approach was, the camera tested as having "phenomenal" preservation of detail up into the very high ISO range. Testing by others, such as from Imaging Resource is still to come.<br> </p>

<p>There eventually may also be a firmware upgrade to further improve the AF. Even with a silver designation, the K-1 did get a rating of 84%, which is very high.</p> <p>This test revealed very low default sharpening for jpegs, but did not get into the control aspects to see how much one can adjust sharpening. With the K10D, the dpreview test revealed inadequate sharpening control for jpeg use.</p> <p>For landscape and portrait photographers, especially those shooting RAW images, the K-1 seems to be a winner.</p> <p>As of now, I remained more interested in the new little K-70.</p> <p> </p>

<p>I am surprised it only received a silver award instead of gold, since it outdid anything ever tested in some respects, even over the 645Z.</p> <p>As to the AF, there are more AF points than previous Pentax models. My impression, however, is once again Pentax trails Nikon and Canon in this regard for tracking of moving subjects. But it may fall in line with other current Pentax models, even with having more AF sensor points. There will be user reports by experienced Pentax photographers as well as other tests published as to whether any AF improvement is noted in the K-1. Accuracy is another matter. Way back in the 1990's tests were done for AF accuracy by Pop Photo, who found faster AF with Canon and Nikon, but they were not quite as reliably accurate. They also found that AF, like any auto system, was not 100% reliable. This test report, however, indicates poor performance for moving subjects. Rather disturbing.</p> <p>I am most interested in the exceptionally fine low noise performance noted in this report. I also noticed dpreview appears to be using a new, and less thorough and less comprehensive way of showing differences in noise performance than in previous testing. That said, the K-1 is rated as extremely successful in this regard.</p> <p> </p>

<p>The K-70 retains the use of the same battery as the K-r and the KS2, which is the D-LI 109. It is very small and light. It also does not last long. Without AA battery capability, it is wise to take along at least one or more charged-up spares in a pocket or camera pack. Not a big deal, since they are so small. But this is one more reason why Pentax really should also continue to offer a pro-style APS-c DSLR in addition to the K-70. Nikon has both amateur-oriented and more advanced APS-c models in the 24mp range. A good idea. With Pentax, one could get a Pro-style model that, while not quite as small as the K-70, is still very compact compared to others in this class.</p> <p>The D-LI 90 battery of my K-5IIs lasts far, far longer than the junior counterpart, and is unlikely to run down while sitting unused, as the smaller D-LI 109 is prone to do.</p> <p>With the advent of these newer, more advanced Pentax bodies, it is more possible that third party lens makers will decide to offer K-mount versions of lenses not currently available for Pentax. Even so, I am with Justin- Pentax has been smart to design WR as a very practical attraction, even in its less expensive bodies and lens lineup. That you do not get in other brands.</p>

<p>Another good choice for APS-c would be the latest Sigma 17-70mm f/2.8-4 which has better than average closeup capability, and better than average speed. It has also come in very well in test reports. Of course, you don't get WR, and the lens front does reportedly rotate when focussing, making the use of rotational filters more inconvenient to use.</p> <p>Test wise, however, the Pentax 16-85mm comes in even better, and offers WR, but apertures are not as fast as the Sigma's are for low light shooting, reducing DOF, or getting up higher shutter speeds without raising the ISO.</p>

<p>Well, a "walk around" lens is not usually a portrait lens, although having greater portrait capability would add still more to its versatility, IF it has wide angle capability too. A versatile "walk around lens" by the most common definition is one that can shoot wide angle, normal, as well as some tele range to handle a variety of scenes. This would obviate the need to carry a second lens to "walk around" with.</p> <p>But, if one is happy walking around with no WA capability, fine!</p> <p>The Sigma 24-60mm f/2.8 is really a moot point, since it is no longer available new. I only brought it up since I have it, to bring up the value I have found of its having some WA, with 24mm vs 28mm being more suitable for a "walk around" lens. I have long had a Tokina 28-70mm f/2.8 zoom lens, but with APS-c I go to the Sigma because of its having 24mm for wide angle shots. There are other zoom lenses available which are 24mm at the short end. My Sigma apparently is just a tad weightier than the Tamron, but the Tamron is a tad longer. The Pentax FA 24-90mm f/3.5-4.5 lens would certainly be a good "walk around " option, but unfortunately it is likewise no longer made.</p> <p> </p>

<p>A while back there seemed to be concern about performance with older high quality lenses made for full frame (35mm film) cameras. Seems like they are doing quite well!</p> <p>Indeed, you can enjoy the now versatility of your Tamron 28-75mm being finally able to shoot wide angle, normal, and tele range photos. I have an old but good Tokina ATX PRO 28-70mm f/2.8 that I could put back in service, among other FF lenses still in my possession. It has had very little use in recent years, being reserved just for film. The K-1 was just tested by POP PHOTO magazine, and they used the old but good Pentax FA 50mm f/1.4 which turned in very fine results. </p> <p>I don't get it regarding the flash. The FF difference should only concern the flash's auto zoom. I often prefer to switch the zoom to manual anyway, using a setting wider than my lens FL for more even coverage.</p> <p>Please do let us know how the low light, high ISO performance goes!</p>

<p>That sounds like a simple question, but it is really a complex one. For the most part, you'd likely not be able to detect an image quality difference between them. All three are capable of rendering very fine results. Each can do some things the others cannot. Where one may shine over the others, it drops to 3rd in another way. That depends on your own shooting needs!</p> <p>If you are possibly interested in obtaining a full frame K-1, it would be the Tamron 28-75mm f/2.8, beyond question. The other two are not suitable for FF use. The other best option would be the new Pentax FF zoom lens, D-FA 24-70mm f/2.8 DC WR which has received very high reviews, along with its Tamron counterpart. The Pentax lens is more costly, but you'd get WR and DC. Also, the difference between 70mm and 75mm at that tele range would be very slight, while the 4mm difference at the short end between 24mm and 28mm is far greater and easy to see.</p> <p>If you are largely interested in telephoto, staying with an APS-c body (as most people do) would be more logical, since getting the same telephoto result requires a less expensive, smaller, lighter, lens. A 100mm lens on a FF body, if put onto an APS-c body, for example, provides approximately a 150mm view field and image. The APS-c body is also more compact and lighter for extensive carrying.</p> <p>A FF body's advantages essentially are in the realm of possible wide angle performance with lower distortion, lower possible noise at higher ISO use, better quality larger possible blowups, since the sensor/image is larger to start with, and greater possible reduction of depth of field. But they are larger and more expensive, and to get high quality telephoto requires a larger lens.</p> <p>Image quality is indeed a complex matter. There are lens factors involved such as light falloff (vignetting), resolution, edge of image performance, far corner performance, center image performance, closer focus performance, distortion, field curvature, color fringing abnormalities, and bokeh (out-of-focus smoothness or lack). There is no such thing as a perfect lens, and zoom lenses are more challenging for designers to deal with these factors. But there are some very good ones.</p> <p>A FF lens on an APS-c body enjoys an advantage. Since it is cut for FF, its extreme corners and edges are omitted from the APS-c frame. This should give it an advantage for edge and corner performance as well as light falloff. But the better APS-c lenses are still competitive. It is difficult to find scientific testing, however, of a FF lens on an APS-c body to compare.</p> <p>If you do a lot of people shots, or of subjects mostly in the central area, the Pentax 18-135mm WR DC would be very fine. Its central resolving capabilities are excellent. Only beyond about 70mm do edges and corners begin to diminish significantly in quality. Even out to 135mm the central area is of high quality. It is quite fine for most any use from wide angle to 70mm. It is very compact and lightweight. If I need corner to corner higher quality beyond 70mm, I can bring along my Pentax 55-300mm WR lens, or if I need even higher edge quality and speed too, I will switch to a pro caliber setup with my Sigma 24-60mm f2.8 EX DG combined with my Pentax DA* 50-135mm f/2.8 WR SDM.</p> <p>The Pentax 16-85mm WR DC provides great performance with exceptional resolution corner to corner throughout its zoom range. It has been awarded Photozone's rare "Highly Recommended" status. You might check out Justin Serpico's threads below. He is very experienced, and shoots very fine landscape scenics.</p> <p>The FF Tamron 28-75mm enjoys a very good reputation for its focal range, especially at its price point for an f/2.8 zoom lens.</p> <p> </p>

<p>I have long had the now unfortunately discontinued Sigma 24-60mm f/2.8 EX DG, which also unfortunately does not have WR or a quiet DC motor. I got a good copy of this model- sharp, even so wide open. It is very compact in size and weight, perhaps even more so than the Tamron 28-75mm. Its 24mm does offer some wide angle for APS-c bodies. It is my second favorite walk around lens. If I am likely to not need the speed, but might need more wide angle, more zoom range or WR, I go with my Pentax 18-135mm for a walk around zoom lens. But if you rarely shoot wide angle shots, use far more telephoto, don't care about WR or noise in a quiet environment, or distracting a subject during candid shots, the 28-75mm may do fine, with an additional wide angle lens for those occasional times a wide angle shot is needed. I see nothing at all wrong if one is happy with this arrangement.</p> <p>For most people,, lacking wide angle capability does not fit the "versatile" category. I'm with Doug regarding that. There is a huge difference in wide angle, and also in overall zoom range between 28-75mm and 16-85mm. The Pentax 16-85mm is compact for such a zoom range, and for its performance over that range. It also has a quiet, accurate DC motor and WR. The Pentax 18-135mm DC WR has even greater zoom range for yet more versatility, and is even more compact in size. Smaller size makes the same weight feel lighter.</p>

<p>Although I have fine "pro" style f/2.8 zoom lenses and excellent "prime" (non zoom) lenses, my favorite walk around zoom lens is my Pentax DA 18-135mm f/3.5-5.6 WR DC. Walk around implies versatility, and I have found this lens has it, with very good IQ. Photozone testing downrated it because they found substandard performance at the image edges when zoomed to the long end. This does not bother me. I do not notice any shortcoming, since when I zoom it to that much telephoto I an generally interested in the center area anyway, which is still very good quality. In other words, I can zoom from a wide angle scene instantly to grab a portrait closeup without having to change lenses. If used in the 18-70mm range, its speed stays pretty good, (f/3.5-4.5) and quality is quite high, even edges. It is very compact for carrying, its DC motor provides AF that is quiet, fast, and accurate. Its field of view is similar to 28-200mm on a full frame body, but it is cut out for APS-c use, so it would have serious light falloff (vignetting) if used on the K-1. The K-1, however, can be switched to 15mp APS-c format.</p> <p>If you need greater wide angle, and high edge to edge quality even when zoomed to its full tele, the Pentax DA 16-85mm WR DC is a very good lens. That advantage comes at a price. It is not quite as compact, yet doesn't have nearly as much telephoto for versatility, even though still good in that regard. Any of this type of lens will have noticeable distortion of straight lines particularly at the widest angle zoom setting. This is normal. This can be avoided by avoiding the widest setting. So if you are using the 16-85mm, and you have say an architectural subject with straight lines near the edges of the frame, you can avoid such distortion by shooting at 18 or 20mm instead of at 16mm. That would be another wide angle advantage for having a zoom lens starting at 16mm over one of 18mm. </p> <p> </p>

<p>That lens is a f/2.8 maximum aperture, if you need such a lens. They are larger, and heavier to walk around with. Designed for full frame bodies, 28mm does not provide much in the way of wide angle for typical DSLRs with APS-c size sensors. If you are thinking of the full frame sensor of the new forthcoming Pentax K-1, then that lens would provide wide angle to moderate tele range. The Tamron lens is also not weather sealed as as are many of the more recent Pentax lenses. You have not stated which camera body you will be using, but many Pentax bodies have weather sealing (WR).</p> <p>Pentax lenses offering both wide angle and tele with WR specifically designed for Pentax APS-c DSLRs are: the small, inexpensive DA 18-55mm f/3.5-5.6 WR kit type lens, then the more premium DA 16-85mm f/3.5-5.6 WR DC, DA 18-135mm WR DC, and if you need the f/2.8 aperture, the DA* 16-50mm f/2.8 WR SDM. The new Pentax D-FA 24-70mm f/2.8 WR is highly rated and will work with the new K-1 full frame model, yet will still provide some wide angle on a regular APS-c model. The very fine Pentax DA 20-40mm f/2.8-4 WR DC Limited is extremely compact and high quality, ideal for a walkaround small zoom.</p> <p>If WR is not of interest, there is the Pentax 17-70mm f/4, as well as some other 3rd party lenses that will go wider than 28mm with moderate telephoto range, or even a super zoom. Pentax makes one- DA 18-270mm f/ 3.5-6.3 SDM.</p>

<p>I also like the AA battery idea. A set of long-lasting lithiums can be found anywhere. I have that feature with my little K-r as a comfort-zone backup, since I tend to be forgetful about charging ahead of time. I use the lithiums only until I get a proprietary one charged up because it is lighter, so those lithiums are lasting a very long time. </p> <p>The K100D was a nice little camera. Plenty good enough for general use and small prints. How "slight" the subsequent image quality advancements depends on this use and one's perception. I still have mine, but have not used it in quite a while. I should get off my behind and sell it. Someone will get a low-use camera for little money. I found the K-200D represented noticeable improvement in IQ in my own case, and a better build with WR. The K-5 series has been even better, with a better VF, again improved IQ with yet greater sharpness and better dynamic range, and lower noise while preserving excellent detail at higher ISO use. I consider my K-5IIs still to be a great performer even among those models now available. </p> <p>The K-70 is too new to expect responses from the usual quarters, and they are a bit slow anyway. I expect the IQ from the K-70 to be on par with that of the K-3, which is very fine indeed. I also expect the build quality to be exceptional for its class, but definitely not up to the K-3, K-5 level. With the features and build it offers, the K-70 should prove to be a great value.</p> <p> But even with the K-70, and the new FF K-1, I feel Pentax should retain the pro-level APS-c K-3, or an upgraded similar model. Let us not just have the K-1 and the K-70. Many of us would prefer to have a pro-level body in both formats. While still having pro-style control features and build, the K-5 series or the K-3, even if owning a K-1, offer a more compact carrying kit with top DA lenses when extensive carrying is needed, and especially when the emphasis will be more in the normal to tele range. The heavier K-1 will be for times when there will be less toting, and where the emphasis will be for wide angle to short tele and for the lowest noise for highest ISO.<br> </p>

<p>I agree with the rough edges to some extent, but the challenge is keeping up with Nikon's 24mp lineup. It does present more difficulty controlling noise at high ISO without losing detail. I was anticipating the new replacement for the KS2 would be one of 24mp.</p> <p>It certainly looks like Pentax has done a great job with the K-70 that offers far more sophistication in advanced features and design, with a more pro-like build than the competition. An outstanding value, despite not keeping up in AF sensors for action shooters.</p> <p>That said, if one does not need the articulated screen and other specific advancements, the K-50 remains by far the best bargain around for great quality still picture shooting, and also has a near-pro build quality with WR, at about 1/2 the price of the (very reasonable) new model!! Its 16mp sensor, as in the K-5 series, has been proven, offering exceptional high quality and exceptional high-ISO performance while losing minimal detail.</p>

<p>I noticed K-50 bodies still in stock at B&H Photo selling for around $300 new, depending on color. Some colors move faster and cost a little more, others move slower and cost a little less. Right now, all black is $306, while a white and black body is at $294. I think shipping is free.</p>

<p>BTW, having more MPs alone does not guarantee more satisfying results. In most cases, beyond a certain point, unless you intend to make a poster size print, or view on a very large screen, you'll be hard pressed to see any difference based on more MPs. 16MPs is a very substantial degree of high resolution in these APS-C size sensors. It is also true that as the MPs go higher, it usually becomes more difficult for designers to effectively preserve detail at higher ISO settings for low light shooting, while smoothing out the increase in noise grain. That is not to say the K-3 does not offer any advancement, such as again with AF speed, but the other models are still very functional. Depends on your particular shooting interests as to how the cost increase might be worthwhile.</p>

<p>The 23MP K-3 current model replaced the 16MP K-5 series. Don't ask me why the model numbers count backwards. These are all professional or advanced enthusiast- oriented camera designs. They have a top LCD display as well as the larger rear LCD screen, and are weather/dust sealed so shooting in rainy conditions with a WR lens attached is no problem. The controls, being of professional design, feature many that are on-body and instantly accessible, rather than accessed in menus, as well as both thumb and finger control dials. The K-5II was an upgrade of the K-5 in several respects, especially the autofocus speed and accuracy. The K-5IIs is built without the usual AA filter, which produces a very slight smoothing to reduce any possible moire artifacts. The omission of this filter is for a slight but definite gain of fine detail resolution. The K-3 is very unusual in that it features a different type of AA filter that can be switched on or off. The K-3II features a built-in GPS locater, but has no built-in flash. All four models are unusually compact and lighter in weight, and less expensive, compared to most other camera models in this class by other brands. All are capable of producing very high quality images.</p> <p>The 16MP K-50 is a terrific bargain. It is designed for the less experienced photographer, having convenient controls for addressing different specific photographic "scenes" for those who may not know what adjustments are likely to be needed for each "scene", i.e. portrait, landscape, etc. It is often chosen by K-3 or K-5 series owners as a second body, because it is even more compact and even lighter, and is most remarkable at such a low price in still having many pro-style features, like weather sealing and both thumb and finger dials, which are not found in models in this class by other brands. You'd have to pay far more to get these advantages. Gone, however, are a number of other on-body controls whose features are now in menus, and the top LCD panel is missing.</p> <p>The KS2 is like the K50, but adds a rear LCD screen that can be pulled out and rotated to more easily use live view to frame shots from overhead or at very low positions. It also upgrades to 20mp and also features the switchable type AA filter. But these additions cost more. As to image quality, you probably would not or rarely see any difference between them.</p>

<p>That's a lot of lenses to be incompatible with. I think it very odd for Pentax to fail in its design of the K-1 for accommodating 3rd party lenses, including those of professional quality, specific to FF models. If it is due to a physical mis-match, we'll have to wait for a K-1n or a K-1/2 to emerge, in order to make use of these lenses. If there is an electronic mismatch, a Pentax firmware update should be forthcoming to take care of it.</p> <p>As to the physical, I just eyeballed my Sigma 24-60mm f/2.8 EX DG and my Pentax 77mm f/1.8 Limited side-by-side with the rear lens caps off. I can see no difference at all of any greater rear projection for any part or rear fitting design. The zoom lens is of course bulkier, but still compact. So I guess that Sigma model, at least, should work ok.</p>