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03-16-2015, 10:35 AM   #1
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How does 645z compare to K-3 in real world ?

Pixel count apart, I'm trying to compare how much of an upgrade the 645z is in reality to the K-3. I'll be trying out a 645z in UK at photo show next week so will get a limited chance to compare the handling.

Here's what I chiefly want:

I use two K-3 bodies with limited primes. Mainly used mounted on a tripod at 100-400 iso. I shoot RAW and process in ACR/PS CC in ProPhoto 16-bit, to squeeze out the most I can from the images.

I can print up to 20"x30" on canvas with excellent quality.

I don't like changing lenses on my K-3s in the field unless I have to, so I'm not sure I would want to with a 645Z. Therefore, I'd probably choose a zoom, which would make the camera/lens quite a lot heavier. Or maybe I'd stick with a prime, perhaps using a K-3 for the longer focal lengths.

The dynamic range of the 645z is probably better on paper than the K-3, but in reality how much better would the 645Z be to the K-3s I own, both in its dynamic range and overall IQ, considering how I mostly use my K-3s ?

Many thanks

03-16-2015, 11:55 AM   #2
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In a way it's like comparing a DSLR to a high-end compact, but on second thought that's not really the case, since the APS-C system gives you a lot more choices when it comes to lenses.

Check out these studio tests to compare the 645Z's image quality to that of the K-3 in a controlled environment:

Pentax 645Z Review - Full-Resolution Studio Tests | PentaxForums.com Reviews

The main advantage of the 645Z is resolution and higher-quality high-ISO photos. But unless you plan to make massive prints, perhaps you should wait for the full-frame, which will still give you a nice increase in IQ while maintaining a similar form factor and a large lens selection.

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03-16-2015, 12:12 PM   #3
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Do you want to print larger than 20x30" and are you unhappy with the DR of your K-3's?

I love my 645Z, but it's a significant cost to jump into the system and it's significantly larger to pack around. Not to mention your selection of modern lenses will drop dramatically.
03-16-2015, 12:12 PM   #4
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Thanks Adam, I appreciate the compact V APS-C comparison, but my usage question was specific. The K-3 resolution at 24mp is great for the 30"x20" canvases I've been printing and as I'm not too concerned about noise at high ISO, my interest is in comparing between the two cameras using my specified conditions - probably not that unusual ie hiking then taking landscapes, with mirror-up, slow shutter, low ISO etc.

I suspect the jump to FF, for my specific requirements, is not going to be that great (especially if the new FF crams in MP at the expense of dynamic range). I suspect the 645Z should be better for me than the K-3, but in reality the question is how much ...?

I take the point about the 645Z lenses, this in fact for me does seem to be a limitation.

---------- Post added 03-16-15 at 07:17 PM ----------

QuoteOriginally posted by Frink Quote
Do you want to print larger than 20x30" and are you unhappy with the DR of your K-3's?

I love my 645Z, but it's a significant cost to jump into the system and it's significantly larger to pack around. Not to mention your selection of modern lenses will drop dramatically.
Thanks Frink.

Larger than 20"x30" ? Probably not, but there's always the fear that a great shot could be better and then printed larger. Getting it filed away to be used some time later it's nice to know the shot was as good as could be taken. But at a cost of weight, fewer lenses etc. might make me use it less ...

Regarding the DR. Happy with K-3, mostly. I can pull out detail in most circumstances, with the latest software, but it would be nice to have more sometimes. How much the 645z has in the real world is to me the key question, when used as I do.

03-16-2015, 12:20 PM   #5
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QuoteOriginally posted by BarryE Quote
I suspect the jump to FF, for my specific requirements, is not going to be that great (especially if the new FF crams in MP at the expense of dynamic range). I suspect the 645Z should be better for me than the K-3, but in reality the question is how much ...?
You get more than twice the sensor area with FF, so it has the potential to be a very big upgrade. Of course we can't comment on the performance of the Pentax FF until it's actually out.

I guess we should start with the basics: what are you unhappy with in the K-3? As I wrote above, the main advantages of larger sensors are lower noise and/or higher resolution. You might be able to squeeze out a little more DR at lower ISOs but the difference isn't that significant.

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03-16-2015, 12:32 PM   #6
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Hi Adam,

I'm happy with the K-3s, but when a lot of effort and time goes into capturing a shot, then knowing the equipment is as good as can be 'sensibly' used is a comfort.

You say "You might be able to squeeze out a little more DR at lower ISOs but the difference isn't that significant."This is what I'm wondering. Obviously, in low light and working to very large prints there'll be no comparison, but for my requirements I can't help wondering...

Thanks for your feedback.

03-16-2015, 12:38 PM   #7
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I haven't used the K3, but I'm pretty familiar with the current gen sony sensors. I don't feel there's a major step up in DR, certainly not enough to justify that sort of upgrade unless there are other factors.

You also should take a hard look at your most commonly used focal lengths and see what prices and size would come replicating your kit for 645, along with the performance/reputation of those lenses.
03-16-2015, 12:47 PM   #8
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Thanks Frink, you've expressed pretty well what I was thinking. Maybe the step up in DR is just not worth it for me, using the K-3s as I do. If the 645Z lens range was more extensive and modern, then the choice might swing a little nearer to taking the plunge.

Still if anyone has used both cameras like I do, it would be great to gear from you ...

I'm thinking that after handling the 645Z next week, I might hire one for a few days (costs around £450, so significant, but obviously less than a new 645z)

03-16-2015, 01:21 PM   #9
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You ought to be able to print much larger than 20x30 with a K-3. I've had canvas prints made up to 40x60 using a K-7 that are nothing short of stunning.
03-16-2015, 02:16 PM   #10
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Hi MPrince, maybe I can print beyond 20" x 30" as you say, I haven't tried. I will do that next, though only as an experiment as I doubt I will often want to go beyond 20"x30.

I agree the K-3 images with quality, modern glass are stunning. At times, though, I just wish I could squeeze more from the DR. I do not like using ND grads, and will bracket and blend if necessary (though I wish I could auto-bracket with mirror locked on the K-3). Maybe the DR differences, at low ISO are slim in reality between the two cameras.

Any comments on the actual DRs of both still very welcome ...
03-16-2015, 02:24 PM   #11
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QuoteOriginally posted by MPrince Quote
You ought to be able to print much larger than 20x30 with a K-3. I've had canvas prints made up to 40x60 using a K-7 that are nothing short of stunning.
I'd agree with this, depending on how far away you're viewing, how much detail you're really after, how much effort you're willing to put into rezzing up the image.

I don't know the exact pixel dimensions, but the K-3 should be around 6000x4000 and the 645z roughly 8200x6150 (close enough). So, at the same native resolution, printing 300ppi, the K-3 gives you roughly 13x20 and the 645z around 21x28, give or take. The aspect ratios are different accounting for the larger jump in the short dimension, and any rezzing up should apply pretty equally to both cameras. If, like me, you prefer a 4x3 or a 4x5 aspect ratio, you're cropping less of the image with the 645z so the advantage increases. If you prefer 2x3 aspect ratio, the advantage of the 645z decreases.

All this is really about resolution, though, which maybe isn't your thrust. As Adam pointed out, the DR isn't so different that you'd notice (at least I haven't at native iso, but I've only had my 645z for a couple of weeks). The 645z would give you more latitude at higher iso's. I tested my z as high as 12800 iso and it was startig to get more noisy than I'd use, but iso 6400 was still good. With the K-3 I really don't like going past 800 if I can help it, and never past 3200.
03-16-2015, 02:43 PM   #12
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Hi jrpower, your 4:3 point is a good one. I too like the 4:3 format, it feels more comfortable to my eye. I often want to go square too, which is something I didn't say and that would give the 645z a big advantage having many more pixels to use.

Beyond 800 ISO on the K-3 does get noisy, but I only use this for the occasional bird in flight shots - not my thing, really. Then of course the lightness and reach of the K-3 would be handy compared to the 645Z, I guess. However, this snap shot of this Red Kite was taken at 3200 and is good at 3500x3500 pixels. So it can stretch nicely beyond 800, sometimes.
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Last edited by BarryE; 03-16-2015 at 02:55 PM.
03-16-2015, 03:12 PM   #13
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QuoteOriginally posted by BarryE Quote
However, this snap shot of this Red Kite was taken at 3200 and is good at 3500x3500 pixels. So it can stretch nicely beyond 800, sometimes.
Nice shot
03-16-2015, 11:37 PM - 2 Likes   #14
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to the OP. Please please please rent a 645Z and do your own testing. My telling you that APS-C isn't even remotely close to the clarity and detail of a 44x33 chip probably means nothing to you. You don't even know me. Rent a 645Z and see for yourself…….

I can go back and print 20x30 inch prints from my *istD that look great , but they don't look any thing like what comes out of a 645Z.
03-17-2015, 12:59 AM   #15
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Hi 672, wise words. Rent it should be. Thanks.
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