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Forum: Pentax News and Rumors 06-02-2013, 04:41 AM

K-3 speculation
Posted By hjb981

Replies: 2,801
Views: 462,096

What about the sensitivities of the sensors (ISO)? If the focal length and aperture are "translated" to the equivalent values for 35 mm, it would make sense to do the same with the sensitivity. The ISO number specifies the sensitivity per unit area, and that makes direct comparisons between different sensor sizes impossible without correcting for the size. Dividing the ISO value with the sensor area and then multiplying by the area of a 35-mm sensor would give a "35-mm equivalent ISO". This could also be called the (total) sensitivity of the sensor instead of speaking in terms of equivalency (and in that case, maybe it would be more suitable with an SI unit, but that is just a matter of a simple conversion factor). Doing this simple calculation, one finds, for example, that ISO 200 in a 35-mm camera is equivalent to ISO 100 in an APS-C camera. At those settings, both sensors yield the same signal given the same amount of light (number of photons), but since those photons are spread over twice the area in the 35-mm sensor, the ISO needs to be twice as high, since it is defined per unit area of the sensor.

Edit: the question I meant to ask was if you heard anything from your friend about the sensitivity -- are there any plans on introducing a measure of the sensor's total sensitivity as opposed to its sensitivity per unit area?

Forum: Pentax DSLR Discussion 10-03-2012, 03:12 AM

Difference between disabling and removing AA filter
Posted By hjb981

Replies: 10
Views: 2,463

The anti-aliasing filter has been removed on the Pentax K-5 II, but only disabled on the Nikon D800E. I am curious as to what the difference is. I can understand what "remove" means, but how does one "disable" an AA filter?

Machine translated quote from an interview with Hiraku Kawauchi, director of public relations for Pentax Ricoh Japan (in this answer discussing the AA filter):
"... There are several cameras that do not have this type of filter, but there are differences. For example, the Nikon D800E has not removed the filter, but it has been disabled. We've completely eliminated. ..."
(Google Translate)

Forum: Pentax DSLR Discussion 09-28-2012, 08:21 AM

Pentax/Ricoh: De-cripple the K-mount! PETITION
Posted By hjb981

Replies: 502
Views: 70,028

I have an old M50/1.7 and an old M135/2.5, and I would really like to be able to use them smoothly with the aperture ring instead of having to stop-down meter. Therefore, I add my vote to the list of people who would really appreciate a de-crippled K-mount. I noticed that I am already in the list in the form of a like, so I am unsure if I should be added again. Actually, what I liked was the initiative to make a list that summarized all of the opinions, making it easier for anyone wanting to see the results quickly to do so. Therefore, the like was not a vote for a de-crippled K-mount, however this post is. I meant to make the post where I added myself to the list earlier (right after liking the initiative of making a list), but something came up unexpectedly and I had to run. Maybe my vote should be changed to link to this post rather than the like. :)

Forum: Pentax K-5 & K-5 II 09-18-2012, 03:19 PM

K-5II autofocus sensors - explanation wanted
Posted By hjb981

Replies: 55
Views: 9,334

I think that you got that right. Put a 2.8 or faster lens on, and the AF will have better precision (be more consistent), in other words, if you focus on the same things many times, there will be less variation between shots.

It also seems that the AF would work with less light, both with a 3.5-5.6 lens and with at 2.8 lens. That is what my original question was about, and does not have to do with how precise the AF work, only how low light levels it can handle.

If I ever write anything that is too technical, do not hesitate to ask. I will try to explain. There are indeed many threads that get very technical, and also lots of incorrect information -- in many threads, someone says "it is this way" and someone else says "no, it is that way" -- obviously one of them has to be wrong. I do not think that anyone here is out to mislead people -- I think most people have the best intentions, but sometimes have misunderstood something. Because of this, you have to be able to evaluate the information you read, and this is of course nearly impossible if you don't have some background knowledge.

In the end, I think that the technical part and picture-taking part are two different (although connected) things. I am interested in both, but if you are interested mostly in the taking-pictures part, don't worry too much about all the super-technical forum talk. As an example, you do not really need to know how many aperture blades your lenses have to take good pictures. If you still want to know to be able to choose future lenses, a basic understanding should suffice: the best situation would be a round aperture. The more blades, the closer to round, so the better. At the "intersections" of the blades (the "corners" of the aperture), the light gets scattered. That means that it "gets spread out". It mostly gets spread out inwards and outwards (towards and away from the center of the aperture). This is the reason for the star patterns that can appear around bright lamps etc in pictures. If you have six aperture blades, the star will have six "spikes". If you have 7 aperture blades, you will have 14 "spikes" on the star. Why? Because remember that each corner causes diffraction in two directions. With on even number of blades, the two diffraction directions of one corner will overlap with the two from the corner opposite. With an odd number, there will be no overlap, and hence twice as many "spikes" as corners, but on the other hand the spikes will be less intense.

OK, the above was very off-topic... I hope that it was understandable, though. The point that I was trying to make is that even the technical stuff does not have to be too complicated. I hope that I was making sense above.

Not being knowledgeable about the technical stuff should not prevent you or anyone else from taking pictures. Like I said, I know several people that do not know that much about the technical stuff, but still take very good pictures.

Forum: Pentax K-5 & K-5 II 09-14-2012, 05:52 AM

K-5II autofocus sensors - explanation wanted
Posted By hjb981

Replies: 55
Views: 9,334

I asked the original question, and I will try to give an explanation as to why I would bother about understanding the technicalities of the auto focus system. It does not have much to do with trying to be a better photographer at all. There were mainly two reasons why I asked the question:
1) I am curious and I want to know how everything works, whether I happen to have some practical use for that knowledge at the moment or not.
2) I wanted to be able to better judge the implications of introducing more precise F/2.8 sensors and claiming a two-stop increase in light-sensitivity.

Before, I could see two alternatives. Either, the improved light sensitivity would only be there when using large aperture lenses, or it would be there for all lenses. If what people have described in this thread is correct, then the case seems to be that indeed the auto focus light sensitivity should likely have been improved for all lenses, and the addition of F/2.8 sensors only had to do with increased precision for large-aperture lenses, and not the light sensitivity.

I find this information valuable, because now I can make a more informed assumption about how the new auto focus system has been improved. Naturally, it cannot replace tests (which will be published soon, when the testers can get hold of cameras).

When the question on how this thread helps anyone being a better photographer was asked, I interpreted it as if there was an underlying assumption that all threads have to be about improving ones photographic skill. I think that both discussions on how to improve yourself and discussions about understanding technical things should be OK -- in fact, if it would only be about improving your own skill, it should be a photography forum rather than a brand-specific forum.

I do not see any problem in being technically interested and wanting to know how stuff works and also wanting to create beautiful pictures. The technical part does not necessarily have to be just a means towards better pictures, but can be interesting in itself.

This does not mean that I only care about the technicalities, and such things. I take pictures and try to improve, also by studying books about composition, light and "telling a story with the picture" and so on, and at the same time I like to understand the technology. Wanting to understand how stuff works and wanting to improve my own technique are not mutually exclusive! I very much am of the opinion that photographers take pictures, and that cameras are tools that are used -- I am very sure that a good photographer could make better pictures with some old compact camera in many situations than I could with my K-5, for example. I know several photographers who I consider better at taking pictures than I, although they know almost nothing about the technology that makes their cameras work.

Lastly, if you think that all of the above seems very strange: try to think of something that you would be curious about, without having any practical use for the information. For example, wouldn't it be fun to know how an airplane can fly, how a loudspeaker works to produce sound or how a light bulb works (substitute something that you find interesting)? That is something similar to how I feel about understanding more about how cameras (and most other things as well) work.

I hope that I was able to clarify a bit. :)

Forum: Pentax K-5 & K-5 II 09-12-2012, 12:22 PM

Realistically how good is the K-5II on paper?
Posted By hjb981

Replies: 20
Views: 4,432

The original K-5 received much praise in reviews, and also from users. It was often described as a very well thought-through photographic tool, with important features accessible through hard buttons, quick and useful hyper modes, the special TAv mode and so on. It also received a lot of praise for its combination of compact dimensions and good ergonomics. The viewfinder was considered one of the best, image quality was second to none for the sensor size and it had the quietest shutter of all comparable cameras. Many features were customizable, such as auto ISO behavior, noise reduction, and also more specialty functions such as flash white balance or whether the white balance should favor a cozy or neutral look under tungsten lightening, so that each photographer could set up the behavior of the camera to his/her preferences.

One thing that was criticized by several users was the auto focus performance under tungsten low-light conditions, and it is my interpretation that this was agreed to be the cameras weakest point by many users - especially considering that so many other things about the camera were top-notch.

I think it was a very good decision by Pentax to keep the already top-notch parts and focus the improvement work on the very important area were it was needed the most: the auto focus system. If the auto focus system is as improved as they say, the K-5 II should be a really great camera by today's standards, in my opinion. The one area were I can see a possibility that the K-5 II would fall behind its competition is the video performance, but I do not know if that will be the case. One thing that was not upgraded is the processor. Even though the Prime II processor is fast enough to not "be in the way" when taking pictures, snappier is always better (as long as it does not mean less battery life). Still the original K-5 was not slow, so I would not consider that a problem.

Lastly, making the screen more readable in sunlight may not look as flashy on paper as for example increasing the number of pixels would, but it is very useful in real life.

Forum: Pentax K-5 & K-5 II 09-12-2012, 02:51 AM

K-5II autofocus sensors - explanation wanted
Posted By hjb981

Replies: 55
Views: 9,334

Thanks, that clarifies things quite a bit. A conclusion would then be that the F/5.6 and F/2.8 points could very well have the same low-light sensitivity -- good news, since it implies that the increased low-light sensitivity would be beneficial both for fast and slow lenses. :)

Forum: Pentax K-5 & K-5 II 09-11-2012, 02:40 PM

K-5II autofocus sensors - explanation wanted
Posted By hjb981

Replies: 55
Views: 9,334

I am posting this in hope that someone knowledgeable will enlighten me (and others, I am sure).

Background: The new K-5II has a new autofocusing system that, according to Pentax, includes F/2.8 sensors in addition to the F/5.6 sensors. The sensitivity is said to be -3 -- 18 EV. The old autofocusing sensor was specified at -1 -- 18 EV, I think. In other words, the low-light sensitivity has been increased by 2 EV.

My assumptions: The original K-5 had F/5.6 auto-focus points and it was specified from -1 EV.

My observation: The difference between F/2.8 and F/5.6 is 2 EV -- the same as the improvement in low-light auto-focus sensitivity.

My conclusion: The improvement in auto-focus low-light sensitivity stems fully from the step to F/2.8 focus points.

Questions:
1) Is my assumption that the original K-5's auto-focus points are F/5.6 correct?
2) Is it as simple as I assume: otherwise identical auto-focus points would improve their low-light performance by 2 EV when increasing the size from F/5.6 to F/2.8?
3a) Does this imply that when used with lenses slower than F/2.8, the camera would use the F/5.6 auto-focus sensors only, and then have the same -1 EV low-light sensitivity as the original K-5?
3b) Or, could the F/2.8 sensor aid the F/5.6 sensor for improved low-light performance if a lens-size in-between was used, like for example F/3.5?

Naturally, there are likely also other improvements of the new auto-focusing system. As an example, since the K-30 had improvements in the form of some kind of light diffuser to decrease the risk of the auto-focus color temperature sensor giving false readings, I would assume that such a diffuser is also on place on the new system. New algorithms were also mentioned in the press release (PENTAX - PENTAX Introduces New K-5 II & K-5 IIs DSLR Cameras).

I would be grateful if someone could explain this in more depth to me.

/Jonas

Forum: Pentax K-5 & K-5 II 07-14-2012, 02:31 PM

Can anyone explain Custom functions C2-10&11
Posted By hjb981

Replies: 3
Views: 1,465

Glad to help. =) I was investigating those modes a bit myself last winter, to find out how to get the correct white balance when using a filter in front of my flash.
Jonas

Forum: Pentax K-5 & K-5 II 07-13-2012, 03:44 PM

Can anyone explain Custom functions C2-10&11
Posted By hjb981

Replies: 3
Views: 1,465

C2-10:
1) Auto Adjustment
This option allows for automatic fine tuning of the white balance, so that instead of selecting one color temperature, you select a range (The following are just made-up numbers, but gives an example of how it could work: instead of setting a single value of say 2800 K (about where tungsten would be), the setting would be 2700--2900, and the camera would decide where in that interval to put the actual white balance). The advantage with this is some flexibility even when a fixed setting is chosen.
2) Fixed
This option means that each setting corresponds to just a single color temperature. The advantage is consistency between shots.

C2-11
1) Auto White Balance
This means that the camera will use its auto white balance when in flash mode, even if you have set a different white balance (when you set a white balance, it will only affect non-flash shots, and the camera will override your setting when in flash mode).
2) Unchanged
This means that the camera will use whatever white balance you have set even when in flash mode. If you use this and set white balance to tungsten, the flash light will look bluish in the pictures. If you use it and set white balance to cloudy, the flash light will look yellowish or reddish. I personally use this setting to be able to use a color filter (gel) on my flash without getting color casts in my pictures. For example, I might put a filter on the flash (not on the lens!) that converts daylight (similar temperature as flash light) to 3200 K, and then set manual white balance to 3200 K, shoot indoors with flash and get ever so slightly yellow incandescent lights instead of very yellow incandescent lights, in other words, I match my flash color temperature to the indoor lighting, and doing so I must also adjust the camera white balance. For this to work, option "2) Unchanged" must be used.
3) Flash
With this setting, the camera will always override the white balance setting you are using, and use flash white balance instead (in other words, the white balance color temperature is set to match the flash).

Forum: Pentax SLR Lens Discussion 07-03-2012, 05:26 PM

Lens Experience Israel Trip: DA 18-135 & Sigma 10-20
Posted By hjb981

Replies: 6
Views: 2,616

If you buy an after-market focusing screen, they usually come with a handy tool for r&r (remove & replace). Perhaps you could get such a tool if you plan on taking the screen out (I am not sure where to look without getting a screen though, which is obviously not justified just to get a simple little plastic pair of tweezers). Another tip is to put some lens paper over the mirror during r&r to avoid damaging it. Lastly, make sure that the battery is out of the camera, to avoid accidental activation of the mirror.

Anyways, I would also rather wait and just leave the dust where it was, until I was sure that I had covered all the hows and ifs on the r%r process. It is a bit fiddly, and there are obviously parts that you do not want to damage in there, and as you say, it won't hurt the pictures. Another option may be to have a service place do it. It should not be too expensive, because it is a pretty fast thing to do if you know how to do it (for me it took maybe half an hour, but I guess I could do it in 5 minutes if I practiced a little).

Forum: Pentax SLR Lens Discussion 07-02-2012, 01:09 PM

Lens Experience Israel Trip: DA 18-135 & Sigma 10-20
Posted By hjb981

Replies: 6
Views: 2,616

Thanks mgvh for the travelling report. I just wanted to chime in and say that I like the lens too, and that maybe you can clean up your viewfinder.

If the viewfinder got dusty, and you can see the dust particles, chances are that the visible dust is on the focusing screen (or on the bottom of the pentaprism if you have one -- I guess pentamirror cameras have air next to the focusing screen on both sides). The focusing screen can be removed and cleaned. One has to be a bit careful not to damage the screen, mirror or any other sensitive part, but it can be done. I have done it for another reason -- changing to a KatzEye split prism focusing screen.

As for traveling, I have also used the 18-135 with good results on my K-5 for over a year (as long as I have had the camera). Since I walk around a lot and carry all of my stuff, I bring as few and light things as possible. The camera plus lens is a big part of the weight I carry, and the smaller aperture and thus lighter weight was the reason I originally wanted the 18-135. I still like the lens, although lately I have mostly used my most recent addition (not for traveling yet, though): the FA 31 ltd, which I also like a lot. Those two are the only modern lenses I own, and I have no plans on getting any other lenses anytime soon (in other words: I am happy with them, and have no plans on macro/super tele/super wide at the time being, maybe later though ;P). I also have an M50/1.7 and an M135/2.5, and I used the M50 a little for indoor club photography (really dark) once, as well as concert shooting (also once).

Forum: Pentax SLR Lens Discussion 06-27-2012, 07:28 PM

Lens Geometry Question
Posted By hjb981

Replies: 60
Views: 5,320

Just as a sidenote (maybe to obvious, thus not mentioned), but it is of course possible to stop down for example a medium-format camera and use a longer shutter time if one wants to attain a deep DOF. This is one reason why you might see a medium-format camera being used with a tripod even in bright light (another being usually higher pixel count, making smaller vibrations visible, and yet another being that anyone shooting medium format is likely to be more particular about perfection, and thus use a tripod when many other photographers would consider handheld good enough :P).

I agree with Class A about the use of the word light-gathering, even though I can see that it could be interpreted both ways. These relative numbers (ISO, aperture) are very useful, but coming from them (like most if not all photographers do), some of the implications can be a bit elusive (like for example that my K-5 sensor gets about the same amount of light in total at ISO 800 as my LX3 sensor does at ISO 80, if the same F-number and shutter speed are used).

I think that make a good point, lytrytyr -- having text as the only medium for discussing makes it much more challenging, and often two people will interpret the same sentence or even word differently.

Forum: Pentax SLR Lens Discussion 06-27-2012, 03:10 PM

Lens Geometry Question
Posted By hjb981

Replies: 60
Views: 5,320

Exactly! If the F-ratio is kept constant, the absolute diameter of aperture will increase when the focal length increases. Therefore, it will let in more light in total, in order to achieve the same illumination per area unit on the sensor plane of the larger sensor (remember that the FOV is kept constant, and hence the total light-gathering area is bigger for the longer focal length). However, the two images will not be equivalent. The image on the larger sensor will have a shorter depth of field. To achieve the same depth of field, the absolute apertures have to be the same, implying a smaller F-number for the larger sensor (remember that the camera-to-subject position as well as FOV are kept constant).

Another approach: imagine having a piece of good old film, say ISO 100. Suppose that your light meter told you to choose F/8, 1/100, you did this, and got a good exposure. Now suppose that you put your film in a camera that exposes half-sized frames on the same roll of film (half-sized by area). Just like you say, you can use the same light meter, and set the camera in the same way, F/8, 1/100. Suppose that you wanted to take a picture from the same spot, with the same field of view. To do this, you would have to choose a lens with a shorter focal length to get the same FOV. With the same F-ratio, the absolute aperture diameter would decrease, just like you say. Since we use the same film in both cases, the total amount of light (number of photons) that it can receive per area unit without overexposing is the same. Lets say that the full-sized frame was correctly exposed and received 1000 billion photons in total. That means that about 500 billion photons exposed the right side, and 500 billion photons exposed the left side (if we assume an evenly lit scene) to give a correct exposure. Now consider the half-sized frame. It is exactly the same size as either side of the full-sized frame. If either side of a full-sized frame is correctly exposed at 500 billion photons, then the half-sized frame must also be correctly exposed by 500 billion photons. This means that at F/8, 1/100 and half the size of the same kind of ISO 100 film, half the amount of photons in total will be used to expose the film, so that the number of photons (amount of light) per area unit is the same (at the same F-number (aperture ratio) the absolute area of the aperture for the half-sized frame will be half of that for the full-sized frame because of the shorter focal length -- it all comes together). This is why we use relative apertures (F numbers), so that the light meter works for all film sizes and focal lengths -- F/8, 1/100 will always yield the same amount of light per area unit, and hence will expose ISO 100 film in the same way, no matter what focal length or film size we choose. However, the images will be different depending on those choices, and in the case of decreasing both the film size and the focal length to receive the same FOV, the depth of field will increase, as will noise because of the smaller amount of photons in total (even though it is the same ISO 100 film in both cases, it will be enlarged twice (area-wise) as much when a half-sized frame was exposed, and this will make noise more visible).

I encourage anyone who does not agree with the above to find a large-sensor and a small sensor camera with lenses that can be chosen for the same FOV on both cameras. Then set both of them to the largest F-number that both lenses allow, the same shutter time and the same ISO. Take the same picture with both cameras, on a scene where there is lots of depth to show out-of-focus areas. Focus on something that is not too far away, to get easy-to-see out-of-focus areas both in front of and behind the focal plane. Then compare the two images. The effect should be very visible, unless you use a very slow aperture.

About the review on the Q: Here is a quote from the review:
"... This relates to the size of the camera sensor which has a crop factor of 5.5x so in full format terms we are talking about "47mm" thus a standard lens. Now this is not the full story. The max. aperture of f/1.9 sound fast and it is terms of light gathering. However, if you apply the cropping factor (f/1.9x5.5 = ~f/10.4) things will appear not all that sexy anymore regarding the depth-of-field potential. ..."

They say exactly what I am trying to explain! Yes, F/1.9 is fast in terms of light gathering, but remember that it describes how much light is gathered per area unit. If the sensor has a smaller area, it will receive less light in total. They even mention that the Q's 8.5 mm F/1.9 lens is equivalent to a 47 mm F/10.4 on FF (meaning that you will get the same FOV and depth of field, and hence the same amount of light in total, meaning less light per area unit and thus a higher ISO for an FF 47 mm F/10.4).

Again, since light meters, F-values and ISO numbers all relate to the amount of light per area unit, it works no matter what format or lens you use. The images will be exposed in the same way if those numbers stay the same, but the images will not be equivalent in terms of depth of field for different frame sizes.

Forum: Pentax SLR Lens Discussion 06-27-2012, 04:08 AM

Lens Geometry Question
Posted By hjb981

Replies: 60
Views: 5,320

Dear all,

I will butt in and try to clarify some of the concepts. I hope it will be helpful, and I have highlighted what I believe to be the most important concepts.

It is true that f/2.8 always means the same light gathering ability as measured per area unit of the sensor. That means that 1 square centimeter of the sensor will always see the same amount of light from a 2.8 lens (if it is pointed towards the same even light source, say a clear sky or evenly illuminated wall for example). So while the amount of light per area unit of the sensor (or film) stays the same, the total amount of light that the sensor gathers will be proportional to the sensor size.

For those less into theory, and more into trying: just take two cameras, one with the biggest sensor you can find, and one with the smallest sensor you can find. Take a shallow depth-of-field picture with the big-sensor camera, then try to make the same picture with the small-sensor camera. Same picture means same distance from camera to subject, and same field of view. It will not be possible to for example reproduce the shallow depth of field of a FF f/2 70 mm on a compact camera that has a sensor 1/20th the size of the FF. This is quite noticeable if you regularly use both kinds of camera.

The below discussion is rather theoretical. I have tried to make it clearer by highlighting the most important parts, and I would urge anyone reading it to do his or her own thinking. In other words: consider the arguments, make drawings of different sensor sizes (that is what I did) or whatever you do to grasp a new concept.

The ISO number also measures the amount of light per surface area unit (just like the F number). That means that a large sensor gathers much more light in total at the same ISO setting as a small sensor, because the amount of light per surface area unit is the same, and it has a bigger surface area. If you look at for example the DXO ratings and compensate for this, given the same amount of light in total, big sensor do not perform better than small sensors. However, with a big sensor, you have the option of opening up the aperture and sacrifice depth of field and gather the same amount of light in total with a shorter shutter time. If I take a picture with my Panasonic LX3, at its maximum aperture F/2 at ISO800 and at its shortest focal length, 5.1 mm in a dark place, I will get a crappy-looking (noisy) picture, with the equivalent field of view as 16 mm on an APS-C camera (24 mm on FF). If I wanted to reproduce that with my K-5, and get the same depth of field and shutter time, I would have to use a 16 mm lens at F/6.3. Since I want to keep the shutter time the same, and F/6.3 allows less light per surface area unit of the sensor, the sensor's sensitivity to light per surface area unit will have to be increased, which means that I will use a higher ISO setting -- in this case about 8000 (which means that the sensor in the K-5 has an area about 10 times as big as the one in the LX3). In doing this, the total amount of light hitting the sensor in the K-5 would be the same as in the LX3, only spread out over a larger sensor. Of course, I could use the 16 mm lens on the K-5 at F/2 and also keep the K-5 at ISO800 (shutter time still the same). That would render a much cleaner image with less noise than what would be possible to achieve with the LX3, but that image would also have a shallower depth of field than the one from the LX3, and hence they are not equivalent.

Yes, a 5.1 F/2 is a 5.1 F/2 on all sensors, but I think it should be quite clear to everyone that putting a 5.1 mm lens on the K-5 would render an image that is very different in terms of field of view compared to using the 5.1 on the small-sensor LX3. It makes much more sense to compare the equivalent focal lengths (5.1 mm for the small sensor and 16 mm for the large sensor).

Dear all, please consider what Class A wrote and give it some thought. Read the articles (s)he is linking to! (S)he is right.

Forum: Pentax SLR Lens Discussion 06-27-2012, 02:53 AM

the pentax FA 31mm f 1.8 al limited, are there bad ones?
Posted By hjb981

Replies: 45
Views: 6,909

You are right -- I had forgotten about that. I always use center-weighted metering, and therefore never noticed it, but spot metering could produce over-exposure when small-aperture lenses are used (2.8 or smaller for the KatzEye screen I have in my K-5). A workaround could be to use exposure compensation with small-aperture lenses, but of course this is an extra element of hassle.

Forum: Pentax SLR Lens Discussion 06-26-2012, 03:19 PM

IQ of Legacy Lenses
Posted By hjb981

Replies: 85
Views: 15,018

I just posted this in a different thread, but realize that it may suit well here: Manual Focusing with AF Camera Systems. Even though it does not have to do with the IQ of old lenses per se, understanding how modern D-SLR:s are different from classic SLR:s when manual focusing lenses could be good to know.

Forum: Pentax SLR Lens Discussion 06-26-2012, 03:16 PM

Legacy IQ comparison
Posted By hjb981

Replies: 11
Views: 1,637

Sometimes computer systems behave oddly ;). Glad that it works now!

Forum: Pentax SLR Lens Discussion 06-26-2012, 03:13 PM

the pentax FA 31mm f 1.8 al limited, are there bad ones?
Posted By hjb981

Replies: 45
Views: 6,909

Sorry if this is getting off-topic, but for those wanting to learn more about focusing manual lenses on modern cameras: Manual Focusing with AF Camera Systems

Forum: Pentax SLR Lens Discussion 06-26-2012, 02:57 PM

the pentax FA 31mm f 1.8 al limited, are there bad ones?
Posted By hjb981

Replies: 45
Views: 6,909

That is a very good point!

Forum: Pentax SLR Lens Discussion 06-26-2012, 02:52 PM

Legacy IQ comparison
Posted By hjb981

Replies: 11
Views: 1,637

I also use Firefox, and it scales large images by default. To see them at full magnification, move the mouse pointer over the image (which turns the pointer into a magnifying glass with a small plus sign), and then I click on the image -- that worked for me on the linked images of the teddy bear.

Forum: Pentax SLR Lens Discussion 06-26-2012, 02:41 PM

the pentax FA 31mm f 1.8 al limited, are there bad ones?
Posted By hjb981

Replies: 45
Views: 6,909

That does not make sense to me... I do not understand how a lens could be made poorly such that it was very hard to focus, but also very sharp and well-performing once focused correctly. That sounds very strange to me, but I may be missing something.

Anyways, the stock focusing screen of the K-5 will show all the un-sharpness of the 90 mm lens when focusing, but not so for the 31 mm. The reason for this is that the screen actually does not show the light below F/2.8 or something like that. The reason for this is that it is optimized to look bright with slow zoom lenses, and a side effect is that you do not see the light hitting it at more gracing angles (the light from a big aperture, like 1.8 for example). Therefore, I think that a split-prism focusing screen will indeed help with the issue, Cachibache, only I suspect that the issue is not the lens, but rather that the stock focusing screen is simply not designed to be used with fast lenses.

I have both a KatzEye split-prism focusing screen and an FA-31 (AIV, bought new). Both are a joy to use, and the lens is really sharp across the frame on my K-5. My KatzEye screen has their OptiBrite treatment, which makes it nicer to use with my slower 18-135 WR zoom (also AIV, as all of them are), but slightly decreases the ease of focusing the fast lens in bright light (according to KatzEye -- I have not tried any of their screens without OptiBrite). I got the FA-31 after the screen, so I have not tried it on a stock focusing screen. I have no complaints on the 18-135 either, although obviously it cannot compete with the 31 when it comes to across-the-frame sharpness at larger apertures (it even cannot achieve very large apertures -- it is F/3.5-5.6).

If you do get a KatzEye or other after-market screen, you will likely have to re-shim it. The thickness of the KatzEye is different from that of the original. Some people will argue that it does not matter because the focusing takes place on the backside of the screen, and hence the distance is the same no matter the thickness of the screen. While it is correct that the distance will be the same, the light-path is not. Any light that hits the screen at a non-perpendicular angle will be refracted, and this happens "sooner" if the screen is thicker, and it therefore will need to be re-shimmed to move it ever so slightly closer to the lens (away from the pentaprism).

A note on the auto focus speed of older lenses: I do not think that it has to do only with the amount of mass that has to be moved, but also on the throw. I think that older lenses tend to have more throw, which means that the angular distance that things have to be moved is longer. This makes precise manual focusing easier, but auto focus slower.

Forum: Pentax SLR Lens Discussion 06-26-2012, 02:04 PM

IQ of Legacy Lenses
Posted By hjb981

Replies: 85
Views: 15,018

I get part of your point -- photographers take pictures, and cameras are tools for doing so. If someone gets the same kind of camera that a good photographer uses, that someone will not automatically become good photographer. I agree with this. However, I am not sure how to interpret "... since he got the new camera he is mostly silent concerning the topic ..." -- does that mean that he preferred the Canon or that he was disappointed with it too?

Forum: Pentax K-5 & K-5 II 06-26-2012, 04:57 AM

Best camera in the world
Posted By hjb981

Replies: 41
Views: 6,483

You are absolutely right about the jpeg engine not mattering if you shoot raw. Personally, I use a big memory card, and always shot both at the same time. I would estimate that I just take the jpegs in more than 99% of the cases, and only use the raw files for some special photos where I want to adjust something more than what the jpegs allows (like lifting the shadows a lot or extracting the last bit of highlight information). Shooting only raw and developing each image is way to tedious for me. For someone that does shoot raw, I could think of two camera-specific things (except the lenses) that could effect the results: the AA filter and the color filters (the Bayer-pattern array of red, green and blue filters in front of the pixels). I am not sure if the AA and color filters are different between different brands using the same sensor, but I think that it might be the case

Thanks for enlightening us (especially me). I really like how Sony has improved sensor and battery technology, and now I can have a little less mixed feeling about them. ;) (Sony was the company that introduced usable lithium ion batteries back about 20 years ago.)

Forum: Pentax K-5 & K-5 II 06-25-2012, 04:40 PM

Best camera in the world
Posted By hjb981

Replies: 41
Views: 6,483

There are definitely more things to making the out of camera images than just the lens and the sensor, namely the cameras jpeg engine. I have heard others mention elsewhere that Sony's jpeg engine is not as good as the rest, and I have also heard elsewhere that the Pentax jpeg engine is one of the best. From my own experience, I tend to agree with the latter (I cannot say about Sony because I do not have that much experience with their camera -- Sony was pretty much off my list of possible choices after I realized that they went and changed the one standard that all the other manufacturers still stick to -- the flash hot-shoe -- and made their own -- completely unnecessary engineering, with the only purpose of making it more complicated for the users (us) to buy anything non-Sony, which is also why you will find "Sony special hot-shoe" to normal hot-shoe adapters -- a completely unnecessary cost for Sony shooters, and one more part that can break or get lost when using non-Sony flashes).

Of course, the exact same reasoning goes for the lens mounts -- of course it would be great for all of us that use cameras if all lenses were compatible with all cameras -- but here, all manufacturers are the same since a long time. That is not the case when it comes to professional video recording equipment. I was talking to a journalist and a camera man some time ago, when I realized that he had a Sony video camera with a Canon lens on it. I asked, and he said that "sure, there is an industry standard for the lens mount. We mix them all the time". Unfortunately, we "personal users" cannot put the same kind of demands as the professional market. Too bad...

Sorry about all the off-topic ranting. Ii's just that I am allergic to that kind of engineering, which is only meant to cripple the products and not to improve on anything.

So, some people like the CCD better than the CMOS. Even if there could have been changes to Pentax's jpeg engine between K10D and K-5, of course what you put into it will also effect the output. CCD:s are less sensitive to the angle of light hitting it, afaik, which I belive is the reason they use CCD:s for the largest sensors (like medium format). Maybe that has something to do with it...

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