下面是Lunatic的体会内容，写得比我的更详细。由于他同时也泡国外的论坛，所以是用e文写的。
I just came back from a local gathering of photographic friends and the main propose for me was to closely examine a pre-production *ist DS that was borrowed from Pentax Japan and brought back from Tokyo to Beijing for a short stay. The following will be my initial thoughts after handling the camera along with its DA 18-55 kit lens. Please remember that this is a pre-production unit (it has a sticker that says "Working Sample" on the bottom) and the firmware of the body is 0.31. I read elsewhere that the firmware version of the Photokina sample was around 0.20. Recent official sample pictures posted on Pentax Japan Web site have version 1.00 in them. As an owner of the *ist D for more than a year, I brought my *ist D along and will provide some hands-on comparisons of the two.
First of all, the body material and finish feels the same as the *ist D. The hand grip is deeper and I get a firmer hold compared with the *ist D. Unfortunately no battery grip can be attached as there are no electronics contacts at the bottom of the *ist DS.
The viewfinder looks as large and as bright and there's no problem with manual focusing. The viewfinder display layout is completely different with no vertical scale on the right side. When using exposure compensation there is a digital display at the lower side (e.g. +1.0). Still no ISO display in viewfinder although it adds an "MF" sign when I switch to manual focus.
The 2-inch LCD on the back is a big step forward from the one on the *ist D thanks to a much higher resolution (more pixels). Reviewing is a pleasure and images appear much sharper on the *ist DS. A nice plus: When you turn the camera on or change modes, the back LCD will temporarily displays the current exposure mode, single or continues shooting, etc. but the information does not include current ISO setting. This could be added in firmware easily. The *ist DS now supports histogram display during instant review mode but there's one drawback here. In instant review, the histogram chart is positioned higher on the screen because there's a delete sign below it. This causes the histogram to block most of the center of the review image, preventing the user from seeing the subject clearly. Either move the chart back down or add some transparency to it will be great.
Now let's talk about a missing Hyper mode and a "hidden" Hyper mode in the *ist DS. The missing mode is Hyper program. When using P mode, you will not be able to shift the exposure combination by using the thumb dial. I guess I'd use Av mode more often if I owned this camera. The "hidden" mode is Hyper manual. While there's no Green Button on the *ist DS, in M mode you can press AE-L and the camera will set the shutter/aperture to the correct value as a starting point for you.
And now the GREAT NEWS: I brought my 20-year-old M 50/2 lens tonight and tried it on the *ist DS. After enabling a custom function to allow shutter release on aperture values other than A, I was able to shoot with the M lens. What about metering? You may already have guessed the answer: Press the magic AE-L button and the camera will do stop-down metering for you and then return to full-open. In other words, in M mode the AE-L button on the *ist DS acts like the green button on the *ist D (firmware 1.10 or higher) and allows metering with older non-A lenses.
With the *ist DS, flash exposure compensation control is now back in the body instead of on the flash. I tried my AF360FGZ on the *ist DS and the compensation setting in the body menu clearly worked. I wasn't able to switch the flash mode to wireless P-TTL on the *ist DS because it's not present in the flash mode menu at all. However, in Phil's preview "Wireless sync" is listed. I guess that this feature had not been implemented in version 0.31 yet.
Compared with the *ist D, the shutter noise/mirror slap noise is slightly higher pitched. I was able to feel that the mirros slap on the *ist DS is heavier and probably causes slightly higher vibration. Remember this is a pre-production unit and a production model might improve in this area. The good news is that Pentax kept the 2-sec self-timer with mirror lock-up.
I only had a 64MB SD card that I borrowed so I was only able to take a few full-size JPEG shots and one RAW image indoors. The RAW file is around 10MB but neither Pentax Photo Lab 1.1 nor C1 3.5.2 could open it. I guess right now only Photo Lab 2.0 can handle it. It's not fair to talk about image quality with firmware 0.31 installed but I'll try to post a couple of images tomorrow morning. From my initial observation, the *ist DS has higher in-camera sharpening than the *ist D and its metering system seems to be very accurate under complicated lighting conditions (inside a restaurant).
The DA 18-55 lens has similar build quality to the DA 16-45 and it's a lot more compact. It fits the *ist DS perfectly and the balance is great. I wasn't able to do any extensive testing with its image quality due to the lighting conditions at the time. I tried to observe how the variable maximum aperture work with this lens. While it's f/3.5 at 18mm, it quickly becomes f/4.0 once I get past around 20mm and becomes f/5.6 before it reaches 55mm. I still prefer the 16-45's constant f/4 but at a price of around or less than US$200 the 18-55 could be a good value.
Regarding basic operations (startup, shutter lag, etc.), I did not notice any differences compared with the *ist D. I didn't measure startup time but it's at least as fast, if not faster. AF speed seemed quite similar and both cameras had no trouble focusing inside the restaurant although I still think the SAFOX VIII system is not as good as the MZ-S (SAFOX VII) in low light conditions. In general, the *ist DS is a pleasure to operate and does not have any "cheap" feelings at all. As an owner of the *ist D, I am glad to report that the four-way controller on the *ist DS is a huge improvement. The OK button is now separate from the outer four-way switch and everything feels very responsive. Some tasks such as changing metering mode requires going through the menu and thus takes longer to accomplish. I guess this is where the *ist DS feels like an entry-level camera.
When you throw in the pricing, I have a strong feeling that Pentax has a winner here. Going down in price from the *ist D to the DS, Pentax did not get rid of any important features (the ones I miss most is Hyper Program and an option for a battery/vertical shooting grip) and instead keep the great viewfinder, same body chassis material, same metering and AF system and same compatibility with older non-A type lenses. From my limited use, I feel that the *ist DS doesn't have the tendency to underexpose (especially when used with the AF360FGZ flash) so Pentax might have improved the metering algorithm. I hope a future firmware update for the *ist D can provide similar improvements to the existing users.
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