[matroxication]

Hello All,

I have purchased Pentax DFA* 70-200 (Brand New) few weeks ago and took few pictures with my daughter at f2.8, 200mm from various distance and am not getting sharp images using phase detect when compared to Live view which nails the focus accurately almost every time.
So as usual, I put my service hat and started calibrating it as usual with every other lens. But am having hard time in getting the calibration right since this lens confuses me all around. Every method I tried, indicated calibration value from -ve spectrum to +ve spectrum. I used 200mm at 2.8 for calibration.
Below is what I have tried so far:

1) Used SpyderLENSCAL : Tried with near distance and also at 30 feet distance. Near distance stated lens is back focused and hence I tried calibrating it to +4 setting which seems good. Weirdly even -4 seems to have made it better and I have no idea how and why. Tested camera taking pictures in my balcony and around my unit and everything seems to be ok. But when I took it outside for a spin in park with my daughter, the focus is kind of hit and miss and I cannot get sharp image of her and live view does it correctly all the time. Even when the shutter speed is not high and slight shake, live view still nails the focus.
2) Tried the DOT Tune method and then it came up with +4 setting. Surprisingly, it also seemed better when I tested with multiple pictures. Also tried taking pictures at infinity and it compared well with live view images. Still took my camera outside for various distance and again its hit and miss. Also next time when I tried DOT tune, it pointed to different value.
3) I even tried a method from online which suggested to take image in live view and also multiple images on every calibration value. From -10 to +10 and compare the image size. Idea is that the right calibration value will have image size similar to live view since it should have nailed the focus every time. Got the value as +7. But again, the focus is not consistent.
4) Used DIY method of using measuring tape and it was back focusing and tried to fix that. Still its not good for all the distances.

I spoke to CR Kennedy who is the authorized service center for Pentax in Melbourne and they wanted me to ship the camera and lens for calibration. I already sent my Pentax K1 and Sigma 35 1.4 art multiple times and had to spend nearly half the cost of lens in shipping and insurance. Plus am not comfortable in sending the camera again since I have seen how some postal service personnel handle things. Hence wanted to check if there is any other method that I can use to get this right before making my decision to send it for calibration.

My expectation is to have sharp images at 2.8 in 200mm using phase detect focus. The only reason I spent lot of money in purchasing this lens is to use at this aperture. Also, I tried all testing with Tripod and monopod to avoid user error but the live view nails it every time when compared to the phase detect. Hence not sure where am making it wrong. Am using Sigma Ceramic filter and even tried couple of pictures without the filter as well.
The queries I have is:
1) Why calibration on both the end of spectrum seems to work better sometime. Never had this issue with other lenses since it either back focusses or front focusses.
2) Cant the phase detect focus match Live view focus on the focus accuracy. Is that always going to be hit and miss with phase detect?
3) Lot of times, its hard to differentiate the image sharpness between the calibration value. I had to pixel peep really hard to try to identify. Sometimes the image is with similar sharpness across multiple calibration value, and every time I compare them with live view image.

[pschlute]

Cant the phase detect focus match Live view focus on the focus accuracy. Is that always going to be hit and miss with phase detect?

PDAF is never going to be as consistent as LV autofocus, but you should be getting 8 or 9 out of 10 correct. Fist I would give the mirror box a clean with a rocket blower using the menu to lift the mirror. This should clear any debris on the AF sensor.

Lot of times, its hard to differentiate the image sharpness between the calibration value. I had to pixel peep really hard to try to identify. Sometimes the image is with similar sharpness across multiple calibration value, and every time I compare them with live view image.

Image sharpness should be identical on all test shots. What you are looking for is where the plane of focus is. You need a robust testing regime. Camera on a tripod, remote release , use a test chart. Every time you change the AF Fine adjustment you should do 10 tests at that setting....making the camera focus the lens from extreme settings (infinity/closest focus distance) each time. Do the tests under natural light. Try and avoid any shutter speed in the 1/30-1/180 range to eliminate the possibility of shutter shock.

Post your results on here.

[matroxication]

Thanks pschlute. I thought I had a hard time in calibrating Sigma 35 1.4 lens but this one is even harder. After I purchased this lens, almost all the pictures which I took is just for calibration. Used almost every time in the house hold that I can think of for calibration The challenge is, one calibration setting is not resolving the issue across all focal length and distance. This is the second zoom lens I have and not sure if thats the behavior. Took this picture in the park and few of them yielded similar results.

---------- Post added 07-05-21 at 02:47 AM ----------

Not to mention, I calibrated the lens prior to taking to the park. But looks like the calibration is not good for all focal length and distances with this lens. Anyone calibrated DFA* 70-200 successfully and if so, which method to use?

[AfterPentax Mark II]

Matroxication, I feel for you. If you buy this expensive camera and this expensive lens you may expect it to be tip top. No problems with getting things right. This kind of experiences on this forum prevent me from heavily investing in Pentax branded gear. Fortunately with the gear I bought in the last year or so I have not had any problems, such as the new KP and the DA* 11-18mm and the DA 35mm F2.4 to mention some purchases. But I am afraid to buy the new K-3 Mark III and the lenses such as the DA F*70-200, just because of the experiences I see on this forum. That there are problems with new camera's and lenses, that is alright, but nowadays it is so hard to get it solved by the service centers that Ricoh works with.
On the other hand, I always used Pentax after learning the tricks of the trade using Zenit camera's "When I was Young" and I do not intent to buy another brand. So that makes it a bit difficult, but perhaps I am being hard on myself? I do not like changes, that is one thing, but changing to another camera make, no way, I'd rather stop making pictures. So only thing I can do is continue with my Pentax lenses and camera's. And if they fail me....

[bratzmahn]

Hello All,

I have purchased Pentax DFA* 70-200 (Brand New) few weeks ago and took few pictures with my daughter at f2.8, 200mm from various distance and am not getting sharp images using phase detect when compared to Live view which nails the focus accurately almost every time.
So as usual, I put my service hat and started calibrating it as usual with every other lens. But am having hard time in getting the calibration right since this lens confuses me all around. Every method I tried, indicated calibration value from -ve spectrum to +ve spectrum. I used 200mm at 2.8 for calibration.
Below is what I have tried so far:

1) Used SpyderLENSCAL : Tried with near distance and also at 30 feet distance. Near distance stated lens is back focused and hence I tried calibrating it to +4 setting which seems good. Weirdly even -4 seems to have made it better and I have no idea how and why. Tested camera taking pictures in my balcony and around my unit and everything seems to be ok. But when I took it outside for a spin in park with my daughter, the focus is kind of hit and miss and I cannot get sharp image of her and live view does it correctly all the time. Even when the shutter speed is not high and slight shake, live view still nails the focus.
2) Tried the DOT Tune method and then it came up with +4 setting. Surprisingly, it also seemed better when I tested with multiple pictures. Also tried taking pictures at infinity and it compared well with live view images. Still took my camera outside for various distance and again its hit and miss. Also next time when I tried DOT tune, it pointed to different value.
3) I even tried a method from online which suggested to take image in live view and also multiple images on every calibration value. From -10 to +10 and compare the image size. Idea is that the right calibration value will have image size similar to live view since it should have nailed the focus every time. Got the value as +7. But again, the focus is not consistent.
4) Used DIY method of using measuring tape and it was back focusing and tried to fix that. Still its not good for all the distances.

I spoke to CR Kennedy who is the authorized service center for Pentax in Melbourne and they wanted me to ship the camera and lens for calibration. I already sent my Pentax K1 and Sigma 35 1.4 art multiple times and had to spend nearly half the cost of lens in shipping and insurance. Plus am not comfortable in sending the camera again since I have seen how some postal service personnel handle things. Hence wanted to check if there is any other method that I can use to get this right before making my decision to send it for calibration.

My expectation is to have sharp images at 2.8 in 200mm using phase detect focus. The only reason I spent lot of money in purchasing this lens is to use at this aperture. Also, I tried all testing with Tripod and monopod to avoid user error but the live view nails it every time when compared to the phase detect. Hence not sure where am making it wrong. Am using Sigma Ceramic filter and even tried couple of pictures without the filter as well.
The queries I have is:
1) Why calibration on both the end of spectrum seems to work better sometime. Never had this issue with other lenses since it either back focusses or front focusses.
2) Cant the phase detect focus match Live view focus on the focus accuracy. Is that always going to be hit and miss with phase detect?
3) Lot of times, its hard to differentiate the image sharpness between the calibration value. I had to pixel peep really hard to try to identify. Sometimes the image is with similar sharpness across multiple calibration value, and every time I compare them with live view image.

I also bought a brandnew DFA 70-200 f2.8 a few years ago - and have the same problems!
Everytime the focus was a tiny bit wrong and I never had a chance to resolve the problem with the AF-fine tuning
But it was brand new and sent it back to the seller...he put it to a Pentax repair service and a few weeks later I get it back: absolutely sharp and focus on spot!
The lens was decentered! With such failure there is no chance to fix it by yourself...maybe your lens is also decentred?

[matroxication]

Thanks bratzmahn. I googled about de-centred issue and everything pointed to edged being soft in an image. Probably will test with Zeiss star lens chart to see if its decentered. How did you confirm on yours that its decentered?

[bratzmahn]

Thanks bratzmahn. I googled about de-centred issue and everything pointed to edged being soft in an image. Probably will test with Zeiss star lens chart to see if its decentered. How did you confirm on yours that its decentered?

It was only a suggestion...I can't confirm it, but after it returns it was really "as new" and the enclosed writing pointed to such a cause...

[pschlute]

But looks like the calibration is not good for all focal length and distances with this lens

That can often be the case with zoom lenses.

For the bird picture, what AF points are you using ?

[matroxication]

ok sure, thanks bratzmahn. I did a test using star charts but could not confirm if its decentered. Used my monitor instead of printing it out.

[Paul the Sunman]

My DFA* 70-200 and K1 needed no calibration. Perfect from day one.

I hope you can sort it out. The easiest option may be to return the lens.

If it were me, and the time for returning the lens hadn't elapsed, that's what I would do - return that one where you bought it and buy another copy. If it can't be calibrated by someone such as yourself who obviously knows what he's doing, then the lens is defective. I'm also assuming, of course, that this behavior doesn't appear with any other lens on that same K-1 (i.e., it's not the camera that's busted).

[bdery]

But looks like the calibration is not good for all focal length and distances with this lens.

That's the point. Pentax are nice in offering a calibration function, but it's limited. A lens might need different settings at different focal lengths and, rarely, at various focus distances.

As others said, I'd exchange it if at all possible.

[DWS1]

But looks like the calibration is not good for all focal length and distances with this lens.

This is a common problem of zoom lenses, and not just Pentax. Zoom lenses are a compromise and are normally optimized for the middle of the zoom range. They may front focus at one end and back focus on the other. Fine focus adjustment is most effective on prime lenses, and less effective on zoom lenses. I would suggest you pick the section of the zoom range you intend to use the most and fine tune the focus for that area.

[matroxication]

Thanks DWS1. Am calibrating using 200mm focal length but getting issues with different distances. I spoke to the CR Kennedy and they requested me to send both the camera and lens. Surprisingly they said they still do the K1 Mark 2 upgrade but am not sure about the cost. Really not sure if its still worth to upgrade to Mark 2 since I have read reviews that its not making much difference and few people got horror stories about upgrade going wrong.

[Paul the Sunman]

I spoke to the CR Kennedy and they requested me to send both the camera and lens. Surprisingly they said they still do the K1 Mark 2 upgrade but am not sure about the cost.

Wow, I thought that horse had well and truly bolted. Whether it is still worth it may depend on your view about how far away is the K1iii. My guess would be sometime in 2022.