645Z-Is Fine AF lens tuning always expected.

[algrove]

I know I must be more thorough, but after reading many of D&A's postings, I realize he AF Fine Tunes each and every lens.

Questions--

Do you have to AF Fine Tune each lens on each 645 body or just copy over the initial data to a second body?

If primarily shooting landscape, do you start with AF fine tuning at infinity?

If using the 150/2.8 for portraits do I assume you fine tune that lens at nearest distance first?

Any and all suggestions welcome since I do believe I have LOTS of work to do in a relatively short period of time.

 

[D&A]

I know I must be more thorough, but after reading many of D&A's postings, I realize he AF Fine Tunes each and every lens.

Questions--

Do you have to AF Fine Tune each lens on each 645 body or just copy over the initial data to a second body?

If primarily shooting landscape, do you start with AF fine tuning at infinity?

If using the 150/2.8 for portraits do I assume you fine tune that lens at nearest distance first?

Any and all suggestions welcome since I do believe I have LOTS of work do do in a relatively short period of time.

Hi Lou,

As I often say...its a bit hard at the moment to post anything lengthy at thr moment since I'm both on my cell phone and at work...but I'll give it a go. Yes, if you have two bodies, often times their AF null point is different, so AF fine tune must be done on both boides with any given lens.

It may be convention to AF fine tune at the min focusing distance of a lens and any shot taken at longer distance whereby its lightly off, should have the larger depth of field at longer distances covering up for any discrepancy. Also lens should be adjusted wide open. This is how it generally wprks with most 35mm DSLR's. Yet as I might have pointed out in older postings, I found better success with regards to 645 lenses, by AF fine tuning a lens wide open at mid distance range. It varies from lens to lens but it's.a good starting point.

I do believe that if you use a lens such as the 150mm f2.8 mostly at portrait distances , you could fine tune lens at that distance for best performance, but depending how much adjustment thr lens requires...ypu might be off at infinity (depending which way you have to adjust AF fine tune (neg or positive direction). I've had instances whereby a lens actually didn't quite focus at infinity if adjusted at close range.

After you fine tune a lens, I'd recommend then double checking for accuracy at 3 different distances...min, mid range, and infinity. You might have to re-adjust based on results and pick a compromise in the actual setting.you settle on.

All files should be examined at 100%. Many don't examine at this magnification and don't realze they are not getting max sharpness from. their lenses.

Legacy lenses most often need critical fine tuning as there is much more variabilty between lens samples vs. the newer WR lenses.

Needless to say all these adjustment should be performed using a tripod.

Dave (D&A)
.

 

[algrove]

Thanks Dave
As I suspected, I have lots of work to do.

I understand your comment about starting at mid distance, but with wides for example I will want near, middle and far in focus and usually dial in a high f stop number to give me plenty of depth of field where I want all distances in focus. I would put the infinity symbol center about one f stop below what I manually dial in just as a safety factor.

Also on the Z there is a selection called "Program Line". Its default is auto. C4 menu (Menu Reference p. R18) brings it up, but appears it only works with "P" mode which I would seldom use as I normally use M mode. However, if I were to use P mode then I would select for landscape the DOF priority (deep). Since I have never seen MTF charts for Pentax 645 lenses I would not choose "MTF priority" although that does sound intriguing.

Just wonder if anyone has had positive experiences with this "Program Line" setting.

 

[Deleted member 7792]

Lou,

I use LensAlign and FocusTune with my Nikon D810 to fine tune focus for each lens with the camera. I was surprised by the amount of lens-to-lens variance there was and by the magnitude/value of fine tuning necessary for precise focus. Lesson learned.

Your question has prompted me to plan to use the same setup with my 645Z and lenses. As you may know, the LensAlign and FocusTune tools are designed to be used at closer focus distances than Dave recommends for the 645 lenses. I'll use those tools as a starting point and evaluate my results. Stay tuned.

Joe

 

[D&A]

Lou,

I use LensAlign and FocusTune with my Nikon D810 to fine tune focus for each lens with the camera. I was surprised by the amount of lens-to-lens variance there was and by the magnitude/value of fine tuning necessary for precise focus. Lesson learned.

Your question has prompted me to plan to use the same setup with my 645Z and lenses. As you may know, the LensAlign and FocusTune tools are designed to be used at closer focus distances than Dave recommends for the 645 lenses. I'll use those tools as a starting point and evaluate my results. Stay tuned.

Joe

Hi Lou and Joe,

Thats the both interesting and confusing thing about using lens align/focus tune when used to AF fine tune Pentax 645 lenses (especially legacy lenses). It makes logical sense to AF fine tune at minimum or close distance (lens wide open) with these tools simply because depth of field for a given lens is at its minimum when focus is set for closest distance (and lens is wide open). As I explained in my post above, when a lens is fined tuned this way, any slight variance in focusing accuracy or even focus shift, will be covered at greater distances by the increase of the depth of field (as focusing distance increases). One would then conclude that at infinity where depth of field is greatest, most any focusing error would certainly be covered. Unfortunately that was not the case in a good number of legacy lenses.

There apparently was a wide varience of how each sample of legacy lens focused and exactly focusing what distance focusing was optimized for. Most of these lenses were constructed and put together in the film era and as such, tolerances were somewhat sloppy. I found with some lenses when adjusting at minimum focusing distance, longer subject focusing would be way off. I'm still not sure of the theory behind this but often times when adjusting a lens at close range, said lens might either not reach infinity focus or might even overshoot it, and correct focus could not be achieved.

It was at this point that I moved back the focusing distance as a starting point, where I first fine tuned a lens and then depending on sample, would check and readjust at different distances if necessary. Compromises often had to be made with some lenses, in order to get acceptable accuracy at close, mid distance and infinity.

Keep in mind fine tuning is done with lens shot wide open. In addition to the growing depth of field at longer focusing distances, the depth of field naturally is bigger when using the lens atopped down. Therefore if one uses their legacy lens at say f9, and also at longer distances, and didn't af fine tune their lens, they may never notice that their lens was "off" or possibly not reaching its full potential.

The one exception to all this was the Pentax FA 120 macro. All samples seem to require almost no AF fine tune. Due to the nature of this lens being a macro lens and thus optomized for min close focusing distance to be exceptional in the macro range, Pentax was very careful to adjust these lenses for near perfect accuracy in focusing. One cannot afford a focusing error where lens is used with a depth of field of an inch or so (in macro range).

Conversely, some of the longer telephotos needed a great deal of AF fine tuning. Part of this is due to the varience too in 645D bodies.

As time went on...the current 645z bodies are factory adjusted to much closer tolerances than the 645D as are many of the lenses now being produced today and as such, AF fine tune is not as critical but I believe still necessary to get best performance.

This is much like the story of early Leica M8 bodies and legacy leica lenses made in the film era. Inaccurate focusing was all over the place and both bodies and and lenses had to be sent in to be adjusted. Since the 645D was Pentax's first 645 digital medium focmat body and it was being used with lenses adjusted in the film era, it too was prone to severe misfocusing with certain samples of lenses combined with bodies that weren't carefully adjusted for "null" (neither front nor back focusing).

As others has aptly pointed out, these annomolies/focusing discrepancies still exist with current Nikon bodies and lenses for example after so many generations of digital bodies and lenses designed in the film era.

Dave (D&A)

 

[algrove]

I have Lens Align (LA), but not Focus Tune (FT). Will check into it.

My LA kit says what to do and then import results into LR and viewing at 100% minimum and basically determine the best correction number..

I did that first with my FA 150/2.8 at 2.8 and it needed no adjustment. Being the lazy guy I am, I assumed that my new lenses like the 25, 28-45, 55 and 90 were made for the 645D/Z so they must have tighter tolerances and did not bother with them since it seemed like I took a solid two hours to get LA all setup and zapped off abouit 10-15 shots and took a look in LR. So that was one lens on one body.

I am thinking I had better get out the older glass and check starting with LA in the house and do some 100 foot testing close by. Inifinity will have to wait, but to me that will be most important for landscape work.

Since I have 2 bodies this will all take forever, but if I want to extract maximum advantage out of this system I better to it NOW.

So to recap what I must do.

1. Start with LA for all lenses on both bodies. To be sure I do not screw this up I assume I set in the C4 menu, and select "Apply One". I see it says the camera will take up to 20 individual lenses!
2. Do this for all lenses wide open and on both bodies.
3. Then download all results into LR and determine the best setting.
4. Then do mid-distance and download and check in LR at 100%. Is 200% just over kill?
5. Finally do infinity and download and check in LR at 100%.

Now to get even more specific. I must assume for each lens at whatever distance I start with zero correction and then with each successive shot go +1 to +10 and -1 to -10 for each lens and both bodies.

Also Dave you mention to recheck. When?

The most important unanswered question to me is--What correction value to I use? If wanting infinity for a specific lens do I then change the Apply One number to my best infinity correction> Then if mostly mid-distance do I then change to my best mid-distance setting?

Also if shoot very wide and I have near say 3-5 feet, and mid at say 100" and I also want infinity in clear focus, what correction number do I use? I can see a vote for using the near number, but with that I might chance getting near and mid, but without infinity in focus. However if I use mid I could miss the near and for me having a near subject out of focus might ruin the shot.

Sorry this sounds all to simplistic, but I want to try to get this right in my mind before traveling over 10 hours (ground+air) to my next shoot and mess it up.

I am sure I missed something, but luckily with Leica I have never had this issue come up thatb I was aware of, but then again I use larger f stop[ numbers for landscape and maybe just lucked out all these years.

 

[D&A]

Hi Lou,

If I omit answering all your questions, its simply that it took forever to type my previous posting on my cell phone and not at a computer. So I'll address the most salient points in no particular order. Let me just say with the Leica system, especially in the early days of thr M8 and M9 and with many legacy lenses...there were many many instances of incoorect focusing. Many though didn't notice or know what to look for or possibly didn't examine their files at 100 percent.

No need to use 200%...100 is sufficient. What you outlined above is mostly correct. You can use lens align at minimum distance and then check focusing accuracy of your files in LR at 100%. After doing so I would urge you to recheck focusing accuracy at mid distance and infinity in any case.

With regards to af fine tune in the camera, use the setting of "one" lens as you indicated for up to 20 lenses. I generally start by testing at -10, -5, 0,+5,+10. Then I examine my files at 100% to narrow down the range I need to set. Lets say the best focusing is between 0 and +5. I then would go back and check every # between 0 and +5 for that lens and again look at files at 100%. If say you had two different 645D bodies...you would absolutely need to do all testing on both bodies. Given that the 645z bodies are nulled with better consistancy, you might want to risk testing one body and use same settings for the other. How close that 2nd body is, is anyones guess.

If you have a given lens that is important to use at a specific distance (say infinity), and best performance at infinity is not achieved when adjusting lens at closer distances, you can opt for optomizing that lens fine tune focusing for that critical distance it will be used at. Keep in mind though that other docusing distances with that lens may be way off. Again its often a compromise.

Again one would assume fine tuning at close range with lens align would be sufficient since any longer focusing distance would have a larger depth of field which would cover for any discrepancy as would stopping down a lens to say f9. Unfortunatelt that was not always the case.

A fellow forum member had tried many samples of a given pentax 645 lens on his 645D and if he optomized for close range, his corners at infinity for landscapes were awful. Some of this had to do with lens sample...the rest because optimizing at close distances didn't quite work for infinity subjects. Strange indeed.

Keep in mind you are using the 645z and so far less varience should be observed with these bodies vs. The 645D....although there is the issue of legacy lens variability.

Oh forgot the most important step. After all testing is done, immediately go to nearest tavern and have a cold one...no make that two! You're going to need it and don't be surprised if you swear off all photography for quite a while and take up knitting as a hobby. .

Dave (D&A)

 

[algrove]

Dave
Thanks for the continued input.

Knitting-NO, but 2 beers=YES!

Still not clear in my mind if I vary my corrections based on subject matter, i.e., use + or - X for near, + or - y for mid distance and yet another correction setting such as + or - z for infinity if using the same lens under varying conditions. Don't know if I made myself clear just now. Perhaps I should have a beer and rephrase it.

 

[D&A]

Dave
Thanks for the continued input.

Knitting-NO, but 2 beers=YES!

Still not clear in my mind if I vary my corrections based on subject matter, i.e., use + or - X for near, + or - y for mid distance and yet another correction setting such as + or - z for infinity if using the same lens under varying conditions. Don't know if I made myself clear just now. Perhaps I should have a beer and rephrase it.

Lou, sit down and have one beer prior to reading what I write (below) and then another after reading it

The problem is if say you adjust a particular lens and settle on a plus (+) or minus (-) setting while adjusting focusing at close range and then afterwards test at infinity and find it needs a different plus (+) or minus (-) adjustment anf set it to that new setting....it will throw off your original close range focusing. The 645z only allows you to imput one setting for each lens. Thats why I urged testing the lens at mid distance as an average setting for distance when first determining the AF fine tune setting for a given lens and then retest at both close range and infinity if the accuracy is close.

If it was like Nikon or Canon af fine tune, then simply testing at minimum distance should be enough to cover the entire focusing range nut as I explained earlier, this doesn't quite work reliably with Pentax 645 lenses in their mediun format digital bodies.

Ok, at this point you should be starting to pour that 2nd beer as instructed...LOL.

Dave (D&A)

 

[algrove]

Dave
Now those are instructions I finally like and will follow to a T. Beer and more beer!

 

[D&A]

Dave
Now those are instructions I finally like and will follow to a T. Beer and more beer!

Lou I found it strange that you questioned my instructions and methodology regarding af fine tuning but when it came to following instructions when and how to drink beer, you followed those suggestions to a "T" and had no issues at all...Lol!

I couldn't help but tease you. Lou its my fault if my instructions weren't clear. My last few lengthy posts were done while I was typing at work on my cell phone and my explanations weren't always clear.

Please let me know how it goes and if you have any additional questions just ask.

Dave (D&A)

 

[algrove]

Thanks Dave. I have started the process and while sipping a beer last night I was trying to figure out where I should consider mid-distance for landscape purposes. It could be all over the map and of course can vary with different lens selection. This might take more beer than I have in the fridge so now I must go shopping before starting this arduous task.

 

[D&A]

Thanks Dave. I have started the process and while sipping a beer last night I was trying to figure out where I should consider mid-distance for landscape purposes. It could be all over the map and of course can vary with different lens selection. This might take more beer than I have in the fridge so now I must go shopping before starting this arduous task.

Lou, mid distance focusing setting for a wide angle lens would obviously be somewhat different than for a long telephoto. Personally I'd put mid distance for a say a 50mm focal length lens around 25-35 feet , so that its aort of in the middle range of its focusing scale. It doesn't have to be precise but different than aay its min focusing distance and also its infinity focus setting.

Dave (D&A)

 

[algrove]

Lou, mid distance focusing setting for a wide angle lens would obviously be somewhat different than for a long telephoto. Personally I'd put mid distance for a say a 50mm focal length lens around 25-35 feet , so that its aort of in the middle range of its focusing scale. It doesn't have to be precise but different than aay its min focusing distance and also its infinity focus setting.

Dave (D&A)

Thanks. So if I put the mid for a 25-28 WA at 15-25 that sounds OK. Conversely for a 90 it might be 45-55 and a 150 it could be 75-100 with the 300 mid point coming in at around 150-175 feet.

Sound like good gueses or would you change any. I was basically calling the nearest mid point at 50% of FL. Of course these comments are made prior to sipping my afternoon beer(s) in contemplation of doing all this "work".

 

[D&A]

Hi Lou,

Those figures for the midpoint sound reasonable but you do know after a few beers, those estimates will keep changing...LOL!

Seriously a precise midpoint range isn't critical but what is important is that both the midpoint and infinity focusing when the lens is tested wide open "is". The closest focusing point of a lens is hardest to get perfectly accurate (when shot wide open), since the depth is smallest at that setting. I did though find some samples of lenses most often off when shot at long distances than at any other focusing distance. Why that was I could never precisely figure out. That's why I suggested not to rely solely on Lens align alone at close range.

Dave (D&A)

 

[algrove]

Dave,
On near adjustment I am just using the Lens Align tables for FF cameras and converting my 645 lenses to 35 equivalent for thispirpose. That's the best I can do. Michael Tapes said he is trying to get his hands on a 645Z in order to run it through his analysis, but I do not have time for that.

So it sounds like I am going to be walking around with 3 sets of data for each lens for each body and then dial in the correction needed for whatever shot I am attempting.

 

[D&A]

I fully understand Lou about three sets of data...although thats a lot of data. I wonder after all is said and done whether for each given lens your three AF fine tune settings for each individual lens...are roughly the same. In other words are the AF fine tune aetting for min distance, mid distance and infinity of each given lens fairly close? I found in many instances they were...with a few very consitant exceptions.

Dave (D&A)

 

[algrove]

OK, So I started with the 28-45/4.5. I am using lens chart from Lens Align (LA), where LA suggests with a 22mm on a FF Nikon for example one should do the near distance at 1.8 ft. The 28-45 documentation says closest focusing is 1.32 ft so I seem to be OK there. I am measuring from front element to the face of the LA chart as opposed to measuring from the focus plane of the sensor. It will do 28 35 and 45 FL measurements even though the lens also shows 32 and 40mm.

I have centered bullseye and all is good. Now I sip a beer.

Using LV I take the shot on M mode at f4.5. Then in review at 100% (x13 on the 645Z) I arrow to the right side to see the DOF scale and it looks really good since the front and rear scales are very close. It seems 1 or 2 notches will zero it in pretty close. So I guess that is nearly perfect. Plus I am thristy again. Any suggestions?
I'd send you a PM except underlined user names I cannot do on this site.

 

[D&A]

Hi Lou,

From what you described, the 28-45 zoom seems really good and I would expect that, as its a very recent addition to the Pentax 645 line of lenses. Just double check thr zoom at infinity. Use the same focal lengths you used when testing close range. It may look sharp at 100% at infinity using the close distant settings for af fine tuning, but that doesn't mean that by tweaking the AF fine tune, you can't improve upon the image sharpness.

I'll be curious how your legacy lenses work out too.

One last thing I forgot to mention. Only have beer nearby to sip when you're fine tuning the newer WR lenses. Stay completely sober and away from drinking while working with legacy lenses since they are not waterproof (weathet resistant) . I actually think thats what Pentax had intended when they designed WR medium format lenses...LOL!

Dave (D&A)

 

[algrove]

Dave
I am starting out with the newest lenses I have decided since they are mostly my go to lenses, i.e., 28-45-,55, 90. Then comes long legacy glass. Thanks again for all your hemp. Will keep you informed.
Lou