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02-14-2010, 03:56 PM   #1
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K7 Lust...

This is Copied from my introductory post, if you want to jjust read my question just skip to the end! Just trying to save a bit of time
Hi there my names Jules and I think I'd like to become a Pentaxaholic!
The journeyman thing, First SLR I ever owned was a Pentax, that gets me in right?
Looong time Nikon user up until a year ago when a new House quickly followed by Redundancy (Lucky me!) changed all that! A bit challanged thru progressive Arthritis meant I could no longer work in Warehousing or for the Military, so I got the chop. Anyway I thought I could get away from my love of Nikon Exotica (I owned quite a list including the D3,D300.D700, 300F2.8 Vr and 200-400 Vr and many more!) and get us the house we wanted (Ecaping from Drug dealers and general scum that I was not allowed go near, got to love the Law!) by buying into a lighter weight/cheaper Canon Zoom system based around a 5DII, Hated it!, So off to College I went to retrain for some more Gentle work and hoping the Money would last which of course it hasn't! In the Meantime I traded my Canon for Sony (a900,16-35mm CZ, 50mmm Macro, 70-300mm G, 70-400mm G) Which although I love gets no use so I'm going to unload that and buy a yet again smaller system due to my Overdraft banging on it's stops. Got to keep going to the end of my College courses or it's al been for nought. So at last to the point!
I'm now back looking at APSC DSLR's, I just don't like where Sony are headed with that line at all, no doubt now I've said that they'll bring out a stormer! Definately don't want to go back to Canon (Just not for me!) Which leaves it between the D300s and the K7, for some reason the K7 just speaks to me? The problem I would have with Nikon is all the memories of the system I had in the past, the K7 just reminds me of the ME Super I started with all those years ago (First decent Camera!) So here I am, rather long but there it is.
Question: AF? Sure it's been beaten to death but is it really slow? When I had a D300 I didn't think it was all that quick when it was in Wide area and AFC, So is the K7 that much worse? I'll get to try one at the End of next week so what should I expect? I shoot mostly landscape but I like to do Airshows a couple of times a year thus provoking my question...Cheers Jules...
Cheers Jules...

02-14-2010, 04:45 PM   #2
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Welcome jules,

I think the K7 autofocus question is one that is difficult to answer. I think that first of all, it is lens dependent. Some lenses are simply faster focusing than others and therefore get to the focus point faster. Some have long focus throws and take a long time (read the DA *55). However, I think that if you look at it versus the D300, what you will find is a little slower autofocus in AF-S mode, but signficantly less ability to track focus in autofocus continuous mode. Falk Lumo did some testing of the K7 and found that it is pretty accurate, but seems to lose a lot of its ability when it comes to tracking random movements (see here).

Just an over all comment: you lose a lot of money switching systems and you will find that there are up sides and down sides to each one. The strong up side to Pentax is smaller bodies and compact primes, but you need to decide if that is important to you or not. I would stick with one brand and not switch. Figure out which brand has the down sides you can live with best and go with them.

Good luck!
02-14-2010, 11:43 PM   #3
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Thanks Rondec.

For the good honest advice! I will wait until PMA to decidebut in the Meantime I'll get to spend an afternoon with the K7
Nikon makes the most Sense to me at the moment (Most of my mates are Nikon shooters and I could borrow or hire stuff if I needed it!) but the K7 just seems to tick all the important boxes with the AF been the only question mark. In the end I can no longer justify the system I currently have being used only about once a week with a Yawning gap in my finances looming, Sad times but I'll bounce back and the K7 Might just be the feelgood ticket!
Cheers Jules...
02-15-2010, 03:03 PM   #4
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In my experience, focusing speed varies greatly by lens and camera model. It seems the screw-drive mechanism gets increased torque with each new camera model, and the K-7 appears to have the most torque so far.

SDM lenses are pretty slow. The micro motor is weak, and it gets weaker with age. I'd put my DA* 50-135mm (SDM) at about the same speed as my 18-55mm kit lens (screw drive) most of the time, except my DA* occasionally has this weird half-second delay before it responds to the auto-focus request. Also, sometimes when I'm using it for the first time in days, it takes 2-3 tries to wake it up before it moves at all. Screw-drive never has any problems like this, its ultra reliable.

On the other hand, my really old F 35-70mm lens (first generation screw-drive auto focus lens from the late 80's/early 90's) focuses faster than greased lightning. This thing locks into focus so quickly, I sometimes get concerned that something might get damaged inside.

I think the big difference lies in the amount of work the screw-drive mechanism needs to do. My old auto-focus lens has a tiny focusing ring (useless for manual focusing) with almost no resistance and a short 90 degree throw. Therefore the screw-drive has barely any resistance to overcome, so it focuses ultra-fast. Meanwhile, my 18-55mm WR kit lens has a much larger focusing ring with a decent resistance and a 110 degree throw. That means the screw-drive has that much more work to do to get the lens focused.

At the other end of the scale, SDM lenses don't have to move the focusing ring at all, it stays put while the camera is focusing. But on my DA*, the throw is like 270 degrees or something ridiculous like that, and the micro-motor generates way too little torque to get things moving very quickly.

I really hope these rumours of an "SDM II" are true. If so, I'll probably be trading in my DA* lens at the first opportunity.

As a point of comparison, I tried out a Nikon D90 the other day with a good, brand new 70-300 lens. I found that it had my kit lens and my DA* beat by a mile as far as focusing speed and accuracy, especially in lower-light situations. But it was no better than my F 35-70mm (except it was quieter, obviously). Only at very low light levels did the 70-300mm get better than my super-old auto-focus lens. I found that Nikon's version of "hunting" involves only a half-sweep through the range before springing back into proper focus, while a Pentax SDM "hunt" involves 2 sweeps back and forth through its range before it finally gives up.

02-15-2010, 03:15 PM   #5
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The Swedish magazine Foto have tested and compared the focusing speed on The K-7, the D300 and the 50D.

Pentax K-7 m. Pentax
DA SMD 17–70/4 SMD:
17 mm: 0,26 s
35 mm: 0,32 s
70 mm: 0,40 s

Nikon D300 m. Nikkor
AF-S VR 16–85/3,5–5,6:
16 mm: 0,34 s
35 mm: 0,36 s
85 mm: 0,38 s

Canon EOS 50D m. Canon
EF-S 17–55/2,8 IS USM:
17 mm: 0,17 s
28 mm: 0,17 s
55 mm: 0,17 s
02-15-2010, 11:59 PM   #6
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Interesting Comparison that...

I wonder how much it has to do with the Lenses light gathering powers too? We all know that makes a difference but the 50D Seems very fast and consistant there using an F2.8 Lens!
When I had one (Believe me I've had nearly all of them over the past couple of years!) It did not seem to be that fast, more "Simple but could lift heavy weights!" Wheras the D300 seemed very complex with a plethora of options (Maybe too many?) and all but single spot having a sort of delay? Almost like thinking time if you know what I mean???
Interesting nonetheless, However the Comments above about SDM worry me a great deal I have to say! Thanks for pointing it out though...
Cheers Jules...
07-13-2010, 05:12 AM   #7
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Journey Continues...

Continued financial strife has caused me to put all my kit up for sale on various forums (Nikon gear and a GF1) and leaves me potentially Cameraless! (is that a proper word???)
leaves me again thinking about the K7 but with what lens I reckon I could swing the body and one decent lens, so is the 17-70 a good choice? Looks like a goodie to me! Would be mostly for Lanscaping and I would add when I can get a job here in the UK again! (A year in College that now feels wasted ) I checked here and on Photozone reviews and couldn't really see anything better but you guys may know different Am I right in thinking this un came out with the K7 so should be a good match?
Yes you are all being pumped for info
Cheers Jules...
07-13-2010, 05:35 AM   #8
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In your place I would go for the Tamron 17-50 and 28-75 f2.8 - very sharp and reliable lenses, the tammy duo roughly GBP 100 more than the Pentax 17-70mm f4.

Advantages of Tamron? Faster AF (yet noisier), better sharpness (but not by a large amount), better low light capabilities, possible bigger warranty period, no risk of SDM failure

Disadvantages? 2 lenses to carry instead of one, 100 GBP more, noisier.

I dislike the SDM issue of Pentax so, if only for that and the f2.8, I would go for the Tamron.

Good luck!

07-13-2010, 06:02 AM   #9
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QuoteOriginally posted by kytra Quote
In your place I would go for the Tamron 17-50 and 28-75 f2.8 - very sharp and reliable lenses, the tammy duo roughly GBP 100 more than the Pentax 17-70mm f4.

Advantages of Tamron? Faster AF (yet noisier), better sharpness (but not by a large amount), better low light capabilities, possible bigger warranty period, no risk of SDM failure

Disadvantages? 2 lenses to carry instead of one, 100 GBP more, noisier.

I dislike the SDM issue of Pentax so, if only for that and the f2.8, I would go for the Tamron.

Good luck!
.... and a lot of pointless doubling on focal length just to get beyond 50mm. A much better choice if you are afraid of the SDM is to get the 28-75 and fill in the lower end with the DA12-24 or better yet, the DA15 at some point. -OR- the 17-50 and later perhaps the DA70. I seriously doubt that on a 15Mp camera, one would seriously miss the gap between 50-70 mm. That is, if the very wide angle is really a need. If not, then just go with the 28-75.

07-13-2010, 07:46 AM   #10
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QuoteOriginally posted by JeffJS Quote
.... and a lot of pointless doubling on focal length just to get beyond 50mm. A much better choice if you are afraid of the SDM is to get the 28-75 and fill in the lower end with the DA12-24 or better yet, the DA15 at some point. -OR- the 17-50 and later perhaps the DA70. I seriously doubt that on a 15Mp camera, one would seriously miss the gap between 50-70 mm. That is, if the very wide angle is really a need. If not, then just go with the 28-75.

Hmm the 28-75 never thought of that one plus the 15 at a later date thats nearly a plan!
Cheers Jules.
tri-elmar-fudd...

Last edited by jules; 07-13-2010 at 07:47 AM. Reason: Sig
07-14-2010, 04:57 AM   #11
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QuoteOriginally posted by kytra Quote
In your place I would go for the Tamron 17-50 and 28-75 f2.8 - very sharp and reliable lenses, the tammy duo roughly GBP 100 more than the Pentax 17-70mm f4.
Either the DA 17-70 is overpriced there or the two Tamrons are extremely cheap... here any of the those Tamrons alone cost almost as much as the 17-70.

But I agree with Jeff, it wouldn't make much sense to buy both Tamron lens.
07-14-2010, 05:06 AM   #12
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QuoteOriginally posted by PFH Quote
The Swedish magazine Foto have tested and compared the focusing speed on The K-7, the D300 and the 50D.

Pentax K-7 m. Pentax
DA SMD 1770/4 SMD:
17 mm: 0,26 s
35 mm: 0,32 s
70 mm: 0,40 s

Nikon D300 m. Nikkor
AF-S VR 1685/3,55,6:
16 mm: 0,34 s
35 mm: 0,36 s
85 mm: 0,38 s

Canon EOS 50D m. Canon
EF-S 1755/2,8 IS USM:
17 mm: 0,17 s
28 mm: 0,17 s
55 mm: 0,17 s
Kind of a crappy test as they let Pentax and Nikon Consumer Zooms contest with a professional canon beast. Nikon and Pentax are equally fast, but I guess the Nikkor 17-55 2.8 would be as fast as the canon and thus way faster than the pentax. I guess a canon consumer zoom (15-85) would have been equal to the SDM and the Nikkor...
07-14-2010, 09:42 AM   #13
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QuoteOriginally posted by JeffJS Quote
A much better choice if you are afraid of the SDM is to get the 28-75 and fill in the lower end with the DA12-24 or better yet, the DA15 at some point. -OR- the 17-50 and later perhaps the DA70. I seriously doubt that on a 15Mp camera, one would seriously miss the gap between 50-70 mm.
Both of these are good suggestions. I would agree that people tend to worry about gaps far too much, and either of these suggestions provides a good useful basic zoom at f/2.8 and another lens to extent the range a bit. I'd be inclined to recommend the 17-50 + 70 for most people, unless you have reason to think you'd really love the extra width of the 15. I suspect most people would need fewer lens changes between a 17-50 and a 70 than they would between a 15 and 28-75. But there are indeed certain types of shooting where the reverse would probably be true - weddings and similar event, for instance.
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