[Jeff Lopez]

I was testing a A50 1.7 and comparing focusing by viewfinder and Liveview. It came out that while Liveview focus was sharp, viewfinder focusing was not. I have tested with other lenses and every lens I have matches viewfinder (green hexagon)and LV focusing perfectly.
I noticed that focusing just before the green hex usually was sharp, but if I focused according to the hex, it would be front focusing..
WB is tuned to tungsten lighting..
My other SMC M 50 1.7 focuses perfect ,VF and LV..
Any ideas?

[pschlute]

Are you doing this test under tungsten lighting?

I have found that artificial lighting "can" affect the accuracy of the auto-focus system, which the green hexagon relies on.

[Adam]

There is tolerance in viewfinder AF confirmation. It's good at getting a ballpark estimate of the optimal focus point, but with a lens that has shallow dof things can still be a bit soft.

If this is the only lens that does this for you I suppose you can try an AF adjustment

[BigMackCam]

I was testing a A50 1.7 and comparing focusing by viewfinder and Liveview. It came out that while Liveview focus was sharp, viewfinder focusing was not. I have tested with other lenses and every lens I have matches viewfinder (green hexagon)and LV focusing perfectly.
I noticed that focusing just before the green hex usually was sharp, but if I focused according to the hex, it would be front focusing..
WB is tuned to tungsten lighting..
My other SMC M 50 1.7 focuses perfect ,VF and LV..
Any ideas?

This isn't an uncommon thing, Jeff. You need to fine tune the AF Fine Adjustment. It's a poorly named feature, really... it's better to think of it as "Phase Detect Focus Adjustment".

[D1N0]

Manual lenses corrections can't be stored in the camera, so any micro adjustments you do for them can only be done with the global correction (of course affecting all your other non corrected lenses.) I rely on the (corrected with shims because Pentax can't be bothered to critically calibrate it) focussing screen (a Katzeye) for focussing, And still it is often off. You need to very critically assess sharpness to get it right. Most secure way of focussing is live view, but I don't like the experience, so don't use it very often.

[Jeff Lopez]

Thanks guys! I AF microadjusted for this lens, without any result..it does work for my other AF lenses but not for my manual lenses, I suppose that adjusting AF only works for F,FA,DA lenses or third party AF lenses..What throws everything out of the park is that it focuses perfectly with 4 manual lenses, LV and VF+hexagon.
I will try again with natural lighting, as pschlute suggested, and ill be updating this post..

[BigMackCam]

Thanks guys! I AF microadjusted for this lens, without any result..it does work for my other AF lenses but not for my manual lenses, I suppose that adjusting AF only works for F,FA,DA lenses or third party AF lenses..What throws everything out of the park is that it focuses perfectly with 4 manual lenses, LV and VF+hexagon.
I will try again with natural lighting, as pschlute suggested, and ill be updating this post..

Just as an FYI, Jeff, AF fine adjustment works on all lenses, AF and manual. I have an old M42-mount Helios 44-2 that requires, from memory, something like -6 adjustment for the focus confirmation to light at the correct position - and my Takumar-A 28mm f/2.8 also required some considerable AF fine adjustment. As I mentioned, it's actually adjusting the phase detect focusing by applying an offset.

It could be, though, that your particular copy of the A50/1.7 is simply outside the range of adjustment. I've yet to experience that on a Pentax prime, but have seen this with a couple of Tamron lenses I own (and subsequently sent in for warranty service). That may be the problem here...

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Last edited by BigMackCam; 04-29-2017 at 06:41 AM.

[Jeff Lopez]

I see Mack..do you think if I use a HDMI monitor it will help af fine tune? I know for sure the dioper is tack on spot..but eyes are tricky nowdays jaja..

[BigMackCam]

eyes are tricky nowdays jaja..

Tell me about it

do you think if I use a HDMI monitor it will help af fine tune? I know for sure the dioper is tack on spot

There are a few ways to go about it. In this instance I'd probably do the following:

1. set the camera on a tripod to ensure it stays in the same position
2. switch to live view and accurately focus on the subject, using magnification to ensure you get it spot on (after this point, don't touch the focus ring)
3. switch back to regular operation
4. set AF fine adjustment to "ALL" (as you can't set individual parameters for an old manual lens)
5. set the level of AF fine adjustment to -10
6. check to see if you get focus confirmation when you half-depress the shutter button (no need to take a photo), and note down whether you do or don't
7. repeat steps 5 and 6, changing the amount of adjustment each time (-9, -8 and so on, all the way to +10) - i.e. go through all of the possible settings

You'll probably find there are three or four settings where you'll get confirmation. Pick one in the middle as your final setting. So, if you find you get focus confirmation with +4, +5 and +6 AF fine adjustment, use the setting +5 in future.

Does that make sense?

[pschlute]

Just humour me...take the lens off the camera and give it a shake...can you hear any of the elements moving at all ?

---------- Post added 04-29-2017 at 06:05 PM ----------

It could be, though, that your particular copy of the A50/1.7 is simply outside the range of adjustment. I've yet to experience that on a Pentax prime

My 31mmLtd needs a 10 adjustment on my K1 to correct back-focus and in truth could do with a 11 or if that were possible ! I have owned it for years and used it on my K10 before which had a split-prism focus screen so I always manually focussed it. The K10 did not have an "official" AF adjustment menu, so I never realised how "off" it was until recently.

[AggieDad]

I'll go the other direction. How about your eyes? Maybe an adjustment to the eyepiece diopter will do it.

[Wheatfield]

I was testing a A50 1.7 and comparing focusing by viewfinder and Liveview. It came out that while Liveview focus was sharp, viewfinder focusing was not. I have tested with other lenses and every lens I have matches viewfinder (green hexagon)and LV focusing perfectly.
I noticed that focusing just before the green hex usually was sharp, but if I focused according to the hex, it would be front focusing..
WB is tuned to tungsten lighting..
My other SMC M 50 1.7 focuses perfect ,VF and LV..
Any ideas?

If your viewfinder is not critically focussing, your choice is to calibrate the optical path (shim the screen properly) or rely on live view or AF.

[Jeff Lopez]

Today, rainy day so Ill be retesting, starting with the DA50..Mack, Im not sure, I kind of remember there is a focusing test procedure using a convex mirror, do you have heard of this? I think I saw something like that from a very old Navy service handbook, not sure though

[BigMackCam]

Today, rainy day so Ill be retesting, starting with the DA50..Mack, Im not sure, I kind of remember there is a focusing test procedure using a convex mirror, do you have heard of this? I think I saw something like that from a very old Navy service handbook, not sure though

I'm not aware of that convex mirror method, Jeff. However, I've fine tuned many lenses - enough that I can usually guess the necessary adjustment within a couple of attempts by now The method I gave you, if you follow it methodically, will work. It's especially suitable for finding the correct setting for focus confirmation on a manual focus lens. For your DA50 and other auto-focus lenses, there are quicker and more accurate methods - but you ideally need some form of focus adjustment chart - at a pinch, though, you can get away with a newspaper, book or ruler.

If you need any further explanation, PM me or post back here and I'll be glad to help