Web Analytics RiceHigh's Pentax Blog: August 2007

Wednesday, August 29, 2007

Underexposure Tendency of K10D and K100D

Last time when I was trying to find some new DA* sample photos, I came across the following nice and interesting sample photo gallery by a K10D user, who have shot and posted quite some pairs of pictures with different Pentax lenses on his K10D:-


Well, when I inspected those comparison shots between the DA* 16-50 against the DA 16-45 as well as those of the DA* versus the DA 21 Limited, I found an obvious irregularity, that is, underexposure. ( Um, it should be "regularity" for Pentax DSLRs, though :-( )

First look at the church photos taken with the DA* 16-50 and the DA 16-45 lenses, I read the EXIF information and discovered that a huge amount of +ve exposure compensation were applied for the two wide angle shots made with the DA* 16-50 and the DA 16-45 at 16mm, i.e., in a value of +1.7EV both for the same scene with the same framing/composition. What does this mean? It simply means that serious underexposure had occurred for the uncompensated metering reading when the shooter attempted to take the shots. Do note also that he put his K10D camera in the Matrix metering mode when he took the pictures.

People may start to argue that the scene is a bit tricky to the light meter for for the lighter wall of church and the bright sky above it. However, I really don't think it is a very difficult scene to be handled with for typical matrix meter with should be somehow intelligent and in this case the K10D matrix / multi-pattern meter simply failed to handle such a situation. And then some people may argue again that the Pentax meter was just trying to preserve the highlight. But I just wish to point out that no blown/burnt out of the sky even after the +1.7EV compensation in the sample pics posted. So, I just wish to ask *what* is/are the camera was trying to "preserve"? What??

So, let's go on to inspect another pairs of photos. This time we can see the church shots taken with the DA 21 lens along with the DA* 16-50 also. The 21mm shot was made with a +0.3EV compensation whereas the DA* 16-50's one was taken with a +0.7EV, which simpy means that the DA* underexposed more than the DA 21, for the same scene with pictures taken at nearly the same time. We can also draw another rough conclusion that the wider the angle in used, the K10D tends to underexpose more when we compare the shots taken at 16mm with the same DA* lens and the DA 16-45, even the two pairs of shots should be taken at a different time which the weather conditions might be different. Well, the K10D user still used the matrix/pattern metering mode and underexposure did still occur, again.

In fact, the underexposure problem of the Pentax DSLRs are the same old problem which seem has never been and could not be cured by Pentax since their old first *ist D. Just look at the set of quick tests and experiments carried out by another K10D user below:-


(Text in Traditional Chinese, you can use Babelfish to translate.)

From the above page, we can see that even fixed pattern metering, i.e., the Spot meter, of the K10D underexposes much and indeed it is rather inaccurate. For a dark mouse, a +ve EV exposure compensation could still be required - this simply violates the basic rule and working principle of light metering for a reflective light meter and is actually rather abnormal amongst all other light meters on Earth which are calibrated to meter correctly for the mid-grey/tone. In fact, with such rather inaccurate Spot meter of the Pentax DSLRs, even of their current "top" model the K10D, the real purpose of a Spot meter is totally defeated as every user uses this mode is supposed to be aiming for the highest possible accuracy and total control in metering. Of course, if a Pentax DSLR user is to adapt for such abnormality, he should always aim at the dark (areas) when using the Spot meter(ing) as an attempt to get proper exposure, but then this is actually very improper, frankly.

And then I can guess some people will still argue that I do not know about the actual condition of the above test shots as I am not the one who was at the site and took the picture. Well, no problem with this, I will show my photo then. Below is a picture took with my K100D on a scene which I don't think is something really very difficult, although the subject was lit by the sunlight:-

I shot RAW and the picture below is the direct original picture without any digital exposure compensation:-

The corresponding *original* exposure histogram actually looks like this:-

Well, in order to rescue the picture to make it looks better again and as close as it could look like as the real scene, a large amount of +ve exposure compensation is inevitable. Actually, to bring it back to the normal sunshine look, a significant large amount of +1.5EV is required, in the Pentax Photo Laboratory. After the correction, the histogram looks more healthy now then, as below:-

But the fact is the whole "corrected" picture now just looks flatter and the building looks less pop than it should be, than *if* proper exposure was achieved *at* the time of exposure by applying the same +1.5EV exposure compensation (but then this *must* require trials and errors *at* the *field* which just means more time wasted but with less photo opportunities - when the time is being wasted, photo opportunities would go away too). Besides, the shiny feel and the colours of the picture becomes a little bit worse too, after the "correction". Now, we have:-

So, proper exposure is *always* the best thing we want and bad exposure and underexposure is just an evil which is *always* undesirable. Well, again any more "preserve highlight" *theory* (by those Pentax defenders)? Well, what can we look from the original histogram distribution above? In fact there is nothing close to clipping, even that we inspect the individual histogram curve for the individual R, G or B colour channel. The whole histogram simply skewed heavily to the left and left *much* room in the right. In my book (and actually in any book about light metering), this is simply called UNDEREXPOSURE.

So, afterall, what's the true advantage of such underexposure if it is really intended. I'm afraid that the true answer is None but the reverse is true. Digital compensation cannot do all the magics but only that inferior picture quality will be resulted - Here is a more detailed and systematic analysis.

To compare with other better DSLRs in the metering and exposure department, take the Canon 5D as an example, which will seldom let me down in shooting under the sunlight, even with bright or even very white subjects and scenes, which the 5D is clever enough or at least much cleverer than the Pentaxes to handle these quite well and yields very satisfactory results with a much higher hit rate and more acceptable results, even when dealing with more tricky scenes and objects. Here are two quick examples, which were made directly out of the camera as in-camera jpegs, just and merely by aimed and shot (no re-touching of any kind has been made except for down-sizing):-

Truly speaking, such kinds of very annoying underexposure problem, with variation with lenses and focal length, etc., is really one of the big reasons to *force* me not to get any Pentax DSLR body "upgrade" further but I need to go with the Canon for a new body not only just for more pixel count.

Unless Pentax is willing and/or able to make a brand new designed body with improved metering and exposure, I think this would be very hard to be acceptable, at least by my own (minimum, I think) standards and requirements. Or, if they are not just so stubborn to not go back to their old but actually reliable 6-segment metering which used in their MZ line of SLRs and quite some popular high end film P&S as well as a few very early Optio DCs, the problem will never disappear, I bet. For a few more examples on how inferior underexposure could spoil photos and how other "proper" DCs/DSLRs can do better (including my old trust-worthy Optio 330 which just has the old 6-segment pattern metering), see my this old *ist D comparison gallery:-


Saturday, August 18, 2007

DA* 16-50 Vs DA 16-45, A Shootout

Here is one of first more formal tests I have seen, which I think is good enough to tell us some truths about the lenses, for a head-to-head comparison:-


(Test report in Traditional Chinese, use Babelfish if required)

Well, as we can see from the pairs of sample photos and the full size crops the author posts, he gives us the following conclusions:-

1. Purple fringing of the DA* is just a little bit better than the DA, but both lenses are considered to be worse than acceptable because the fringes are still obvious for both;

2. The DA* 16-50 consistently underexposes more than the DA 16-45 on the K10D, under a wide variety of shooting situations, as stated by the author. In fact, the two posted sample images by him show this clearly too. The author considers the underexposure of the DA*16-50 is highly undesirable. It is further noted that the DA* may have more light loss which is judged by lower EV values metered but yet the pictures came out to be darker, which is again undesirable indeed;

3. The images from the DA 16-45 are warmer, i.e. with more yellow whilst the DA* 16-50 contains no yellow at all. It is further stated that the DA* 16-50 images look more saturated than the DA 16-45 but anyway the author does point out that this maybe related to underexposure as underexposed images normally look more saturated than normally exposed ones. Personally, I must say I still don't like the "new" tone of the DA* lenses, as I have said before. Regarding this kind of colour reproduction which I don't like, I can find the same thing for many of the other sample photos I have seen on the net, including Ned Bunnell's ones, which I bet quite some we *old* Pentaxians will not like it - we love the *old* tones of those older Pentax excellent optics, but it seems that those were the days. In fact, I found that the DA 16-45 is already cooler than I like (a detailed comparison here) but now that the DA*s are even more blueish!(?)

4. Resolution wise, the DA* 16-50 wins and that the only aspect it clearly wins. The difference will become smaller when stopped down to f/8 or beyond, though.

Nonetheless, do note that the above comparisons are not made with the same aperture numbers, the tester compares the relative stopped-down apertures in the same amount of stopping down step(s). As such, there is always one f-stop's difference in the comparisons. One may think this to be fair or unfair, depending on what one thinks about the rationales.

Besides, I have also found another fair and comprehensive overview by another new DA* 16-50 user here. Actually, he also "coincidently" notes about the underexposure problem too with his DA* on the K10D. Besides, he points out that the AF with SDM is indeed not significantly faster than that with traditional body AF.

Another major problem some other new users have reported about is the high amount of distortion at wide angles, which is obviously more than that of the DA 16-45 (2.52% barrel), which IMHO is too much indeed for a wide lens, not even to say for a luxury classed one as the DA Star. In fact, some of the users believe that the distortion is of the same level as the Tokina ATX Pro DX 16-50, of which the amount is measured and can be visualised here (a 3.55% barrel distortion, which is really *too* much!). My experience is that such large and obvious barrel distortion is a true annoyance when shooting landscapes with the horizons or any horizontal lines appeared near the top or bottom picture frame borders, which will make the pictures look somehow ugly and odd.

So, if one asks me if the DA* worth its price, in particular for the DA* 16-50, I would say "No" without second thought. Actually, I won't recommend this lens as long as there is a much alternative cheaper choice of which the DA* 16-50 is not much better than, i.e., the DA 16-45. With nearly four times the price of the DA*16-50 than a DA 16-45, the small difference in performance and features actually makes the DA 16-45 a no-brainer. Do note that the DA 16-45 does even have some other advantages over the DA* 16-50, as for those discussed above and some other things which are obvious, e.g., it is smaller and lighter and uses a common Pentax thread size of 67mm (which the DA*50-135 uses too).

Wednesday, August 08, 2007

Hoya has Completed Acquiring Pentax

Two official announcements have been out at the Pentax Japanese website:-



It is stated in the above first announment that now Hoya has 90.58% of voting rights of the company Pentax, that is, Hoya is the largest and major shareholder who holds even much more than 50% of the stakes of the compnay and Hoya is also called as "our parent company" in the announment by Pentax. With such a large percentage of stakes owned by Hoya, Pentax is virtually so close to a wholly owned subsidiary of Hoya now.

Besides, in the second announment, it is told that two new directors are appointed for Pentax by Hoya, both are senior officials from the Hoya company and of course this has been agreed and approved in the shareholders' meeting without any problem.

So, let's wait and see how the company will become and see if the Pentax camera system will become ever stronger under the big umbrella or just to be aborted (by Hoya) in the end.

Last Related Article: Finally, It is Done.