I flirted with a Pentax K7

[bakubo]

I flirted with the Pentax K7 this month and I thought some might be interested in what I found. I got a fantastic deal for a new K7 + 18-55mm for US$855 with free shipping and no tax. I had been giving some thought to getting one to try out so when I saw that deal I jumped on it. Sadly, I returned it yesterday. The only reason I returned it was because compared to my A700 at ISO 1600, 3200, and 6400 it was worse. In all other ways that I care about it was a very nice upgrade from the A700. A big bonus is that it was smaller so for travel that would be very welcome.

I shot 3 raw shots in my hotel room a few days ago with the K7 and A700 and ISO 1600, 3200, and 6400 (K7 v1.03, A700 v4, both with high ISO nr off). I used the meter readings for both and got similar histograms. The first thing I noticed is that at ISO 1600 the K7 needed a half stop more exposure and at ISO 3200 and 6400 it needed 2/3 stops more exposure than the A700. Since I only go to higher ISO settings when I need a faster shutter speed this immediately was a problem. Even with that additional exposure I discovered that the K7 had significantly more noise than the A700. I tried both ACR 5.4 and RawTherapee 2.4.1. RT was better, but better for the A700 too. I also tried Neat Image on the K7 images and with careful work improved them a bit, but it also improved the A700 images. Then if you consider that I really should compare the K7 ISO 1600 to A700 ISO 1200, K7 ISO 3200 to A700 ISO 2000, and K7 ISO 6400 to A700 ISO 4000 the K7 looks even worse. Just to reiterate, I am only talking about high ISO.

The camera and its features are really wonderful. Note, for other people very fast AF or fps or something else might be really important. I checked the things that were important to me and the only bad thing I discovered was the high ISO.

If the K7 had the Kx sensor or even the A550 sensor it would be really nice. For me though, I find that when I travel I use ISO 1600 and higher from time to time for people at night on the street, etc. so it is important. It sure was hard to return it, but I decided that even if I kept it I would end up picking up the A700 in preference for a trip and also that with the poor high ISO I wouldn't be motivated to buy any additional Pentax mount lenses. Maybe a K7 update will be out this year though and I bet Pentax addresses this one big shortcoming.

By the way, I wasn't planning to get rid of my Sony gear even if the K7 had worked out better for me.

[bakubo]

Although the K7 is not a Sony I thought some people might be somewhat interested in what I found. Anyway, it is quite nice, but not this version for me. We'll see what Sony has with the A7xx, if they ever actually come out with it. I would prefer not getting into any other system so I can hope Sony comes through and also hope my A700 lasts until then.

[roysmith]

Really nice camera the K7, at least in paper as I never had the chance to try it, if I didn't have the A700 that would probably be my prefered choice. That or the Olympus E3 as I don't care that much about high ISO but need a solid, weather sealed body.
Your comments about being worse than the A700 at high ISO are unexpected, always thought the A700 wasn't that impressive in that aspect and this new semipro body from Pentax should do a lot better. Also the differences in ISO sensitivity... dxomark shows something entirely different, and now I'm starting to believe that those tests (from dxomark I mean) are not that accurate... or maybe it varies between camera bodies... but it shouldn't.

Anyway thanks for the info!

[bakubo]

Here is the dxomark comparison for the A700, K7, and Kx:

http://dxomark.com/index.php/eng/Image- ... %29/Pentax

Although dxomark shows the A700 as better than the K7, the Kx looks quite a bit better than both. From what I saw the high ISO of the K7 was quite a bit worse than the K7 and when you combine that with the lower sensitivity of the K7 it was a no-go for me.

By the way, the K7 is not just really nice on paper. In reality it is great. Amazing number of easily configurable things and many were things I have wished for from Sony and Canon for a long time. Also, AF micro-adjust, weather sealing, etc.

[roysmith]

What I meant with dxomark is that, under ISO Sensitivity, it shows like the K7 has higher sensitivity than the A700 for a determined ISO value. i.e. at ISO 3200 the A700 has a measured ISO of 2378 while the K7 has 2818. This is just the opposite of what your tests revealed, or I'm just confused?

[bakubo]

What I meant with dxomark is that, under ISO Sensitivity, it shows like the K7 has higher sensitivity than the A700 for a determined ISO value. i.e. at ISO 3200 the A700 has a measured ISO of 2378 while the K7 has 2818. This is just the opposite of what your tests revealed, or I'm just confused?

Okay, I see what you mean. This is completely different from what I saw though:

ISO 1600: A700 1/30 f4, K7 1/20 f4
ISO 3200: A700 1/60 f4, K7 1/40 f4
ISO 6400: A700 1/125 f4, K7 1/80 f4

Not sure what dxomark is measuring. They may be correct in some technical sense, but in practical use this is what you actually get. Weird.

[roysmith]

Yes that's quite a difference in sensitivity. Did you shoot JPG or RAW? Dxomark uses RAW as far as I know. If you shot JPG it may be just a perception thing because of the different curves and in camera processing...? Also the lens can make a difference here... f4 is not always exactly f4 as it varies with the lens.

[bakubo]

Yes that's quite a difference in sensitivity. Did you shoot JPG or RAW? Dxomark uses RAW as far as I know. If you shot JPG it may be just a perception thing because of the different curves and in camera processing...? Also the lens can make a difference here... f4 is not always exactly f4 as it varies with the lens.

Yes, as I said in my OP, I shot raw and used both ACR 5.4 and RawTherapee 2.4.1.

Whatever the reason the practical result is that the K7 needed more exposure. I could shoot ISO 1200 with the A700, but would have to shoot ISO 1600 with the K7. ISO 1600 on the A700 is a lot better than ISO 1600 on the K7, but ISO 1200 on the A700 is a whole lot better than ISO 1600 on the K7 and so on.

[Birma]

Interesting to read your thoughts Henry. I really like the specs for the K7 - it has all of the features I would want in a camera. I think it is the camera (feature list wise) that a lot of those waiting for the A7xx want Sony to make, but I suspect the A7xx will miss some of the features in favour of some additional exotica.

[bakubo]

Interesting to read your thoughts Henry. I really like the specs for the K7 - it has all of the features I would want in a camera. I think it is the camera (feature list wise) that a lot of those waiting for the A7xx want Sony to make, but I suspect the A7xx will miss some of the features in favour of some additional exotica.

Yes, my thoughts are the same. I can wholeheartedly recommend the K7 to anyone who shoots at ISO 1000 or less. I can't tell you how hard it was to send it back. I waited until the last day of the return window to do it and even now I am not sure I did the right thing. The K7 with the 12mp Sony sensor that is in the Kx or the 14mp Sony sensor in the A550 would make this camera the one I would probably get.

By the way, Carl Garrard wrote an article comparing the K7 to the A700:

http://www.alphamountworld.com/photogra ... comparison

[KevinBarrett]

I've used my brother's Pentax K20(D) and was very impressed. I like the very professional interface, such as the additional shooting modes, the custom auto-ISO parameters, and the emphasis on a big bright viewfinder, but what bothered me was that 14mp Samsung sensor. The extra resolution was notable when comparing files to my a700, but I saw innumerable hot pixels in the K20(D), which was unacceptable.

What would steal me to Pentax more quickly than the camera bodies, however, are the lenses. My brother's 21mm f/3.2 is corner-to-corner sharp from wide open, and his weather-proof kit lens is not far behind it.

[bakubo]

I've used my brother's Pentax K20(D) and was very impressed. I like the very professional interface, such as the additional shooting modes, the custom auto-ISO parameters, and the emphasis on a big bright viewfinder, but what bothered me was that 14mp Samsung sensor. The extra resolution was notable when comparing files to my a700, but I saw innumerable hot pixels in the K20(D), which was unacceptable.

From what I have read the K7 is a pretty good upgrade to the K20D. Yeah, that 14mp Samsung sensor is not the best. The Sony 12mp as used in the Kx or the Sony 14mp as used in the A550 would be a better choice. Since the main negative of the K7 is this sensor I bet that Pentax will address this fairly soon. For the way I use a DSLR I couldn't find anything annoying or negative about the camera except the high ISO. I have never been able to say that about any other camera. It was just so impressive. Amazing ability to easily configure it the way you want. Clearly real photographers had a lot of input into its design.

What would steal me to Pentax more quickly than the camera bodies, however, are the lenses. My brother's 21mm f/3.2 is corner-to-corner sharp from wide open, and his weather-proof kit lens is not far behind it.

Yeah, from what I have read on forums the Pentax prime lenses are very highly regarded.

[bakubo]

Of course, ISO 6400 is the worst case, but here are 100% crops from the K7 and A700 using both RawTherapee and ACR. Actually, the A700 shots have been uprezzed to the same size as the K7 shots since the K7 is 14mp and the A700 is 12mp. It seemed that pretty much the delta for ISO 1600 and 3200 was similar.

K7 1/80 f4
A700 1/125 f4

K7, RawTherapee 2.4.1:


A700, RawTherapee 2.4.1:


K7, ACR 5.4:


A700, ACR 5.4:

[bakubo]

By the way, my previous post with the crops is not only interesting to compare the K7 and A700, but also the difference in RawTherapee and ACR. I have seen that some people say the newest ACR in LR 3 beta is better than the ACR 5.4 that I used, but I haven't used LR so I don't know from personal experience. I have to say though that I hate using RT. It is buggy and so slow I find it almost unusable. I just used it to check things out in this case though since ACR was not too good for high ISO shots. Results are much better than ACR though.

[bossel]

I haven't used LR so I don't know from personal experience.

I had previously tried LR2 and didn't like it. LR3 is better I feel, the new engine is great and the final release will offer lens correction similar to DXO. If you download LR3 Beta 2 now for free you can use it till end june.

This is A700 at ISO 3200 100% crop. I applied not too much noise reaction, yet I like the result:

ISO3200.jpg (49.48 KiB) Viewed 7789 times