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Thread: 645Z lens for comparison

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    645Z lens for comparison

    DT will be running an extensive tech camera and wide-angle SLR test later this week.

    We will be including the 645Z with 55mm but we want to include a wider lens as well.

    Should we include the 25mm digital (no longer being made), the 28-45mm zoom, or the analog 35mm? Due to the already expansive nature of the test we really can only include one... hence my question here.

    Also, if anyone knows a Pentax rep, or a knowledgable Pentax user to come on the test with us we'd be glad to have one along to make sure we get the most out of the Pentax. It's generally not my thing to include cameras in tests that we don't sell, but we've had so many requests for this kind of comparison.
    Doug Peterson , Digital Transitions | Email
    Dealer for: Phase One, Mamiya Leaf, Arca-Swiss, Cambo, Eizo, Profoto
    Office: 877.367.8537. Cell: 740.707.2183

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    Re: 645Z lens for comparison

    The 28-45 IMO is the strongest of that bunch.

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    Re: 645Z lens for comparison

    Quote Originally Posted by thedigitalbean View Post
    The 28-45 IMO is the strongest of that bunch.
    +1 on the 28-45

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    Re: 645Z lens for comparison

    28-45 would be best. Though it would be tricky to have the corners in DoF. You would need to design a test scene to reflect the corner sharpness. Also, it is said to be a lens for crop sensor.

    I wouldn't bother with the 55mm at all and it would be way better to test the 28-45 and another wide angle (supposed to have full frame coverage). For example, I was told that there used to be a film version of 25mm or whatsoever with fullframe coverage. Or just the rebranded 35mm?

    It would give an indication of how Pentax would perform if Pentax gains access to the 100 MP sensor at all.
    Last edited by voidshatter; 11th January 2016 at 10:50.

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    Re: 645Z lens for comparison

    An idea of a third party to witness the test would be a good idea but since it is highly likely that the outcome wouldn't be in favour of the Pentax (because in my previous tests even with the same sensor the Pentax fell behind due to lens limitations) I strongly doubt that any Pentax dealer would be motivated to assist.

    In the case that you would rely on yourself, I would recommend you using the Live View for manual focusing of the Pentax (press the OK button then zoom in if I remember correctly). Focus peaking is indeed a nice function which surpasses the Phase One digital backs. Also remember to use Mirror Up to avoid flipping of the mirror during exposure. Also remember to disable image stabilisation if lenses like the 28-45 when it is shot on a tripod. That's how I attempted to obtain maximal sharpness of the Pentax when I did the tests.
    Last edited by voidshatter; 11th January 2016 at 10:52.

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    Re: 645Z lens for comparison

    Doug, I would agree with what others have suggested and posted in this thread. I originally tested multiple copies of all Pentax AF 645 lenses (posted on Getdpi) and when it comes to both central but especially edge edge and corner resolution, the 28-45 Zoom is far superior to the 25mm DFA and DA (one covers full 645 image circle while the newer one cover only the cropped sensor) and the older film era designed FA 35mm f3.5 lens.

    Both 25mm lenses and a good sample of the 35mm perform very similary except for angle of view. The 35mm would be the most cost effective of the three by far. Lots of variability though between FA 35mm lens samples. The wildcard and far less expensive lens of all of them could be the manual focus version of the 35mm f3.5 which often demonstrates better edge/ corner resolution than ita AF counterpart (the FA 35mm f3.5) but at same time exhibits more CA. If ultimate sharpness ia the objective, then stay with the zoom.

    Dave (D&A)
    Last edited by D&A; 11th January 2016 at 12:32.

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    Re: 645Z lens for comparison

    Quote Originally Posted by voidshatter View Post
    An idea of a third party to witness the test would be a good idea but since it is highly likely that the outcome wouldn't be in favour of the Pentax (because in my previous tests even with the same sensor the Pentax fell behind due to lens limitations) I strongly doubt that any Pentax dealer would be motivated to assist.

    In the case that you would rely on yourself, I would recommend you using the Live View for manual focusing of the Pentax (press the OK button then zoom in if I remember correctly). Focus peaking is indeed a nice function which surpasses the Phase One digital backs. Also remember to use Mirror Up to avoid flipping of the mirror during exposure. Also remember to disable image stabilisation if lenses like the 28-45 when it is shot on a tripod. That's how I attempted to obtain maximal sharpness of the Pentax when I did the tests.
    Why don't you fly to NY and assist in the tests?
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    Re: 645Z lens for comparison

    Quote Originally Posted by Ken_R View Post
    Why don't you fly to NY and assist in the tests?
    Then someone would think it's done by amateur and invalidate the results

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    Re: 645Z lens for comparison

    Interesting, I've never used the 28-45 but I do have a stack of raws here from it. To my eyes, my old 35/3.5 is better. But thats far from scientific

    The new 35/3.5 also looks very promising and i'll be getting one soon. Sorry Doug if I was in NY I'd head over

    My 35/3.5 is very sharp wide open and is just stupidly sharp at f8-11.

    Doug, when using the 645z to make the most of it, use the 2sec timer - this will auto engage the mirror lockup. Zoom in to 10x in live view to confirm proper focus. It's a good 'little' camera. Set the raws to .DNG and when you open them in lightroom make sure to set the profile to "embedded" rather than adobe standard. The adobe one mucks up the reds.

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    Re: 645Z lens for comparison

    I also wouldn't bother with the 55mm as voidshatter said, it's a subpar lens in regards to corner performance.

    I think the only viable lenses for this test would be the 28-45, New 35-DFA, 90 macro, and 120 macro. These are pretty inarguable about being the best options.

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    Re: 645Z lens for comparison

    28-45 is on it's way. Thanks for the input!

    We will still include the 55; even if it's not that great it is the lens that comes with most kits and is the closest to the 80LS we've already done a ton of testing on with the IQ3 100MP.
    Doug Peterson , Digital Transitions | Email
    Dealer for: Phase One, Mamiya Leaf, Arca-Swiss, Cambo, Eizo, Profoto
    Office: 877.367.8537. Cell: 740.707.2183
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    Re: 645Z lens for comparison

    Quote Originally Posted by dougpeterson View Post
    28-45 is on it's way. Thanks for the input!

    We will still include the 55; even if it's not that great it is the lens that comes with most kits and is the closest to the 80LS we've already done a ton of testing on with the IQ3 100MP.
    I haven't looked closely at corner sharpness on my 55 - but I've found it to be very sharp with good colours. I like the lens, just find it a bit of a weird focal length. The AF hunts a bit as well. I think it'll do decently in your test.

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    Re: 645Z lens for comparison

    I always use mirror lock up and then wait about 3 seconds before activating the shutter with the Pentax waterproof remote ($21). Also calibrating each lens with each body important as D&A will tell you.

    The 55 is sharp to me and the 28-45 is a big but a very good wide. As others have said the 35/3.5 is very good too.
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    Re: 645Z lens for comparison

    Quote Originally Posted by algrove View Post
    I always use mirror lock up and then wait about 3 seconds before activating the shutter with the Pentax waterproof remote ($21). Also calibrating each lens with each body important as D&A will tell you.

    The 55 is sharp to me and the 28-45 is a big but a very good wide. As others have said the 35/3.5 is very good too.
    Yes this is all excellent advice. As mentioned Doug, its very important to AF fine tune any lens being used on a given 646 D or Z body. If you are AF fine tuning the zoom, pick three focal.lengths (28, 36 amd 45) or at least the two (28 amd 45) and AF fine tune and see if settings for the focal lengths chosen coorispond5. Conventional.wisdom.says AF fine tune at closest focusIng distance where depth of field is smallest but thats not alway the case in this system and have found in certain circumstances (especially with legacy lenses) mid distance or longer is best for focus point.

    Dave

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    Re: 645Z lens for comparison

    Doug, thank you for doing this test.

    I expect the IQ3 100 to do very well given the larger sensor and excellent lenses you are able to put on the front. I am not sure the resolution alone would be a huge advantage though.

    With the 645, a more interesting comparison may be with the IQ250. Since both employ the same sensor, it will be a revealing test of the lenses both brands have on offer. Even better would be to put the Pentax lenses on the IQ250 back with a tech cam if that is possible.

    In my own amateur tests of the 645 against the Canon 5DR, the Pentax was way superior esp at the edges, I suspect because the lenses were better and the sensor larger as well.

    Will be an interesting test. Thanks again, can't wait to see what turns up.
    Too much to list, let's just say I have a bad case of GAS.........

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