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K7 AF Myth
- Thread starter Marques Lamont
- Start date
Not appear to what?
Prognathous
Veteran Member
It says more about the lens than the camera. The DA* 50-135 is slow. Do you think the (re-branded) Tokina 50-135 in EF mount would be much faster on the 7D?
That only proves that the 17-55 is about as fast in both directions, it doesn't prove that other lenses are the same. I would expect a $1000 lens with ring-USM to be better than a $100 screw-drive kit lens in many ways, including speed of AF. Wouldn't you?
BTW, you conveniently ignored the hunting issue. Does that mean you concede that the the need to hunt (when the subject is totally out of focus due to minimum focus) affects AF speed?
The only thing that matters when testing AF speed is how long it takes the focus to actually lock and how accurate are the results. Do you have anything to say about these matters regarding this test? Any time measurements or sample to share?
I use Olympus and KM DSLR's and I don't have any Pentax gear, but I do know a poorly executed test with when I see one, and this is an excellent example.
A proper test would use similarly priced bodies (e.g. 7D and 50D, or K-x and 500D) and multiple equivalent lenses (e.g. 18-55 + 50/1.4 + 55-300/70-300); it would measure the actual time (in ms) it takes the camera to achieve a lock (rather than how many steps there are in the process); it would check the resulting focus accuracy; it would make sure both cameras see exactly the same target (using a tripod or at the very least putting the camera at eye level and ensuring the focus point is on targer, unlike this "test"); it would test for both easy subjects (high contrast vertical lines) and tougher ones (low contrast, horizontal lines), it would test the peripheral AF points in addition to the center one, and yes it would test the time it takes the camera to focus when initially set to infinity, and when already set to the correct focus point (like imaging-resource.com does).
Prog.
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http://www.flickr.com/photos/oren_b
Here is one K7 owner's experience:
http://www.youtube.com/profile?user=55bduke#p/u/2/ngUcQUchHEU
Apologies if this has already been posted. He also has 2 other comparison videos.
I've pretty much decided to wait for the K8(?), both for sensor/ISO and A/F reasons.
Cheers
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Best regards
Greg
He who cannot laugh at himself need not worry - others will do it for him
http://www.youtube.com/profile?user=55bduke#p/u/2/ngUcQUchHEU
Apologies if this has already been posted. He also has 2 other comparison videos.
I've pretty much decided to wait for the K8(?), both for sensor/ISO and A/F reasons.
Cheers
--
Best regards
Greg
He who cannot laugh at himself need not worry - others will do it for him
The main time difference in that video appears to be the lens throw being much longer in both lenses used on the Pentax. It's obviously going to take longer to get to the focus point. In the real world, you often have a lens almost focused on the required new subject beforehand, from a previous shot, so it would also be nice to see the times going from say a subject 6ft away to one 8ft away, the response time would then probably be more down to the camera.
"... to have off-center cross AF points..." (my guess).
Steve is partially right here as none of the visible f5.6 off-center AF points are cross sensor.
Still, the 5D and 5DII (same AF sensor) have 3 f2.8 sensitive cross sensors (one visible in the center and two invisible above and bellow) and 4 more invisible assists sensors that are a great help in tracking moving things.
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http://lol-photoblog.blogspot.com/
topgun2007
Leading Member
That is not a well known nor documented fact that Canon takes out of focus pictures just because the AF is quicker. I believe this to be a myth perpetuated by frustrated Pentax owners. For one, I have had Pentax supposedly lock on focus and then find out that it wasn't in focus afterwards. Also, a couple of years ago, I saw great photos of a couple ex-Pentians and their BIF pictures that they captured with the Canon 40D and usually the EF 400mm, f/5.6 which seemed to have very fast AF and was extremely accurate. Also, the 40D was very good in locking in for low light photography and some of the wedding professionals who used Canon FF cameras, used the 40D for the low light work. One disadvantage of the Pentax so far has been that sometimes slower prevents capture of a shot altogether which has happened to me from time to time. I can't speak of the K-x, but I do use the K20D and have called and asked Pentax support whether the K7 is much improved over my camera and they didn't indicate that I could expect a lot better with the K7. Considering that both use basically the same AF system that makes sense to me. At this stage, I can only wait for a K8 and hope that Pentax finally gets it right.
Regards, Jim
--Interesting, I compared AF on my K-x with an associates now ancient Eos 20D and the K-x seemed slow in comparison (using a variety of lenses)
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Rob
Equipment list in profile.
flash1100
Senior Member
nothing to see here, move along please
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Cheers
Gordon
Perth, Western Australia
K-7
http://www.flashpixx.net
http://www.pbase.com/gordonhaywood/
http://www.pentaxphotogallery.com/home#section=ARTIST&subSection=123519&subSubSection=0&language=EN
YOU're kidding, right? Photography 101: yes it matters. Notice how the focus scale on all lenses are not linear.
Return to the Canon forum and ask. Anyone there who has a clue on photography (i.e. go to the 1D forum, not the 1000D) will tell you it matters.
topgun2007
Leading Member
You are exactly right. While I am a Pentax user and have been for a long time but if I could afford both, I would have purchased the 40D also. Now, the 7D has all the good points of the 40D and many more and I definitely would love to have one in my collection for BIFs and sports. Maybe the K8 will make up ground.
Regards, Jim
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Equipment list in profile.
And if you want to try an ultimately fast-AF screw drive lens on K-mount, put on the cheap, old, slow FA35-80 f/4-5.6.
Instantaneous focus on the K-7. I'm not kidding.
Instantaneous focus on the K-7. I'm not kidding.
Myth for you maybe but with 33000 photos on the K10D and 55000 photos on the K20D and having the K20D/K-7 side by side for a few months it became a pain to use the K20D due to its slow focus speed, i traded my K20D for a K-x and the focus is much faster...
if you are getting so much hunting then you either have a bad lens or a bad camera... dust on the AF sensor can cause issues too.
before you claim MYTH maybe you should consider that you are maybe the only person complaining about hunt... hunt... hunt... beep! the rest of us would complain if we encountered the same and we aren't so you're the odd one out
now give us some more information like lens and conditions, sure if you are using a slow lens in a dark room then one might expect such behavior... even my slowest focusing lenses the 77Ltd and Sigma 24mm F1.8 focus noticeably faster
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Mike from Canada
'I like to think so far outside the box that it would require a telephoto lens just to see the box!' ~ 'My Quote'
http://www.airliners.net/search/photo.search?sort_order=views%20DESC&first_this_page=0&page_limit=180&&emailsearch=mighty_mike88%40hotmail.com&thumbnails=
Is it written somewhere that SAFOX uses a form of double checking? I've always thought it's a myth.
To me, K-7 AF is plenty fast, and hunts a LOT less than the K10D (which is already a lot faster than my K100DS) especially in low light.
Anyway, if the double check really exists, you can get around it by putting the body in AF-C mode. It gives the shutter a priority, which means it can stop in the middle of AF and take a shot if you tell it to.
To me, K-7 AF is plenty fast, and hunts a LOT less than the K10D (which is already a lot faster than my K100DS) especially in low light.
Anyway, if the double check really exists, you can get around it by putting the body in AF-C mode. It gives the shutter a priority, which means it can stop in the middle of AF and take a shot if you tell it to.
How about I compare the K100D with the 1DsMk4 and show that the 1Ds doesn't even have SR?
I don't see how it's a lesser shortcoming than the K7 AF in low light. In other words, Canon must be doing something wrong with the 1DsMk4 - and in your logic, 1DsMk4 users should not lie to themselves with "but there are IS lenses", or "but the 1DsMk4 is a FF" "excuses".
I don't see how it's a lesser shortcoming than the K7 AF in low light. In other words, Canon must be doing something wrong with the 1DsMk4 - and in your logic, 1DsMk4 users should not lie to themselves with "but there are IS lenses", or "but the 1DsMk4 is a FF" "excuses".
topgun2007
Leading Member
Alan, I agree with you completely. I had the PZ-1P and that was the best Pentax cameras I have ever owned. I think it did 8fps if I remember correctly and I hardly had any pictures out of focus. At $459, it did everything the Canon and Nikon $1000 cameras did. By the way, are you still using the 40D and has it replace Pentax or are you using Pentax too? Let me know. Thanks.
Regards, Jim
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Equipment list in profile.
MightyMike
Forum Pro
My F35-70 F3.5-4.5 is lightning fast too on the K-7 and K-x
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Mike from Canada
'I like to think so far outside the box that it would require a telephoto lens just to see the box!' ~ 'My Quote'
http://www.airliners.net/search/photo.search?sort_order=views%20DESC&first_this_page=0&page_limit=180&&emailsearch=mighty_mike88%40hotmail.com&thumbnails=
--
Mike from Canada
'I like to think so far outside the box that it would require a telephoto lens just to see the box!' ~ 'My Quote
'
http://www.airliners.net/search/photo.search?sort_order=views%20DESC&first_this_page=0&page_limit=180&&emailsearch=mighty_mike88%40hotmail.com&thumbnails=
W
wlachan
Guest
I am stilling using Pentax, just added 40D to my collection because of the specific zooms they offer and vastly better AF tracking. Z-1p does 4fps actually.
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Alan Chan
http://www.pbase.com/wlachan
Alex Sarbu
Forum Pro
The double check really exists, IMO.
This was something I've empirically tested, though quite unwillingly, with the slow-to-death-in-low-light *istDS.
That camera would take a reading, think a little bit, and then move the lens (more or less - but I had no accuracy issues with that camera) in the correct position. The process being so slow in low light, by the time it's finished the subject to camera distance can easily change, and the camera will 'see' this (the double check) and refocus. Again and again and again, until you get a frozen subject and iron-steady hands.
Of course, I'm talking about AF-S.
Alex S.
jamesm007
Veteran Member
I have read hard evidence but forget were
... but I did find this -"SAFOX
"SAFOX" stands for Sensor Ability Fortifying Optical Compensating System. It has gone through four revisions, with SAFOX-I being used in the SF series AF bodies, and SAFOX-IV being used in the ZX/MZ bodies. All SAFOX-type lenses are fully compatible with all SAFOX bodies. Basically, this means that the SF, Z/PZ, and ZX/MZ bodies are all compatible with all F and FA lenses.
This system works as follows. The main mirror which is semi-transparent in the middle lets a fixed amount of light pass to a small auxiliary mirror at its back. This mirror redirects the light to a light sensitive CCD-sensor which makes a decision on whether the image is in focus, and then transmits an electrical signal to the auto focus chip. This chip calculates the required amount and direction of rotation of the AF motor. The "in focus" analysis is based on phase detection. The light rays which are deflected by the auxiliary mirror are passed through an infra-red filter and then through a lens system that splits the image in two. If the image is in focus, these two images match. If the lens is focused to far, the two images have a greater distance on the CCD line, if it is focused to narrow these two images have a shorter distance then in the ´zero´ position. Out of this image-, phase-shifting the computer calculates the number and direction of rotations for the auto focus motor. It is not possible to stop right now from a full speed focusing to the exact point. So the speed is reduced before the right focus point is reached. The computer of the camera subdivide the number of turns to reach the right focus point. A photo interrupter in the lens count the impulses and send it back to the camera. The camera compares the actual value with the rated value. A certain steps before the rated value is reached the speed of the auto focus motor is reduced. To the motto "Trust is good — control is better" the computer starts a control measuring."
The last sentence hints at the double, triple or whatever it takes to get a perfect max in phase image the Pentax AF will do. Ever wonder what the AF was doing in low light with the click, click, click back and forth, its not confused as much as making sure... in mid to bright light its plenty fast and very accurate, in low light its still good but slower, yes. So the Pentax system does not rely on DOF and looks and looks again... good/bad(?) depends on the user needs, as its probably truthfully the most accurate AF system, maybe not more accurate than the best, but as accurate as it gets compared to any! As stated in the Canon AF paper the Canon system never focuses at the exact plane of perfect focus, it relies on DOF... good, bad, I have no problems with my K20D, but agree its time for an update to the tracking AF, tracking AF is another story all together and Canon fanboys can write what ever they want about Pentax tracking AF, and I will sign it lol. At least with my K20D, don't know how good the K-7 is?
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jamesm007,
http://s195.photobucket.com/albums/z77/jamesm700/
WSSA member 266PX
The K-7 is even bested in AF by the entry level Rebel. Again, look after EV6. (Pophoto.com)
K-7 focus speed results vs EV:
Canon Rebel focus results vs. EV:
People keep throwing in red herrings to ignore the limitations of the K-7 focus speed. It is only competitive with the competition until EV6 (that is brighter than typical indoor lighting.) Even as high as EV3, the Rebel will focus twice as fast as the K-7.
Now go ahead and list all the problems with Popular Photography methodology. The bottom line is that no methodology that shows the K-7 to be slower is acceptable right?
K-7 focus speed results vs EV:
Canon Rebel focus results vs. EV:
People keep throwing in red herrings to ignore the limitations of the K-7 focus speed. It is only competitive with the competition until EV6 (that is brighter than typical indoor lighting.) Even as high as EV3, the Rebel will focus twice as fast as the K-7.
Now go ahead and list all the problems with Popular Photography methodology. The bottom line is that no methodology that shows the K-7 to be slower is acceptable right?
Richard Murdey
Senior Member
It's the biggest difference between my D200 and my K10, and what definitively marks the D200 the superior machine.I just got my hands on a K7. Here is a myth I found out about it:
"Hunt, hunt, hunt... focus, beep."
D200 AF : zi-ip, beep. zi-ip, beep. Even a dimly lit room, even with the multi AF points tuned on. There's no overshoot and no hunting, just quickly ramps down to the right spot and then stops. This is with screw mount lenses.
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