[Ryan Tischer]

I just started noticing some exposure issues with my 645Z where despite having the exact same camera settings, the exposure varies widely from image to image. For example, let's say I'm shooting at 1/60 sec, f/8, ISO 100...I don't change any settings, but from image to image the exposure varies widely.

So far it only seems to do this when using my 645-FA 150-300mm, so I'm hoping it's an issue with the lens (this wouldn't surprise me as I dropped it a while back and cracked the lens hood) and not the camera.

Any ideas on troubleshooting this?

[Adam]

I'd start by looking at the aperture. Does the diaphragm work smoothly and stop down consistently?

[Alex645]

+1 @Adam. Also if you could post 2-3 examples with the EXIF metadata link, that would also help.

[Ryan Tischer]

These were all shot with the same camera settings and shot in rapid succession, so I'm sure the exposure difference wasn't due to changing light.

[Ryan Tischer]

Here's an image, they were all shot with identical exposure settings, but they're totally different exposures when you look at them:

(in case the attachment doesn't work: Expsoure Issue (Image only))

[bwgv001]

Would you have a DOF function on your Z? On my K3II I see a difference in Liveview for different apertures. So you might have a chance to repeat and check brightness of display and at the same time whether aperture closes always the same amount?
Just an idea.

I checked. this should be on page 67 in your manual.

[Alex645]

Ryan, In the attached image, what are we not seeing between these shots? For example between IMG9707 and IMG9710? Or between IMG9710 and IMG9713, or IMG9716 and IMG9718?

Because your lens has a range of f/5.6 thru f/45, with normal set at f/16, it still points to an issue with the aperture either not closing down enough or closing down or sticking closed.

To determine if it's the lens or the camera, trying another lens would probably reveal if it's the zoom lens or the camera.

[Ryan Tischer]

it still points to an issue with the aperture either not closing down enough or closing down or sticking closed.

To determine if it's the lens or the camera, trying another lens would probably reveal if it's the zoom lens or the camera.

I put both my 28-45 and 80-160 lenses on and had no issues, so like you said it may be an aperture issue with the lens, which was also my original suspicion (and what I'd hoped for, instead of a camera issue).

---------- Post added 04-09-20 at 10:20 AM ----------

I just compared my 150-300 lens to one that I know has been working normally...I'm pretty sure it's a sticky aperture because when I stop it down manually using the aperture ring and then move the little lever (or whatever that's called) it opens back up slowly, instead of instantly like my other functioning lens.

Now, the question is...can I get it repaired anywhere? Or does it just need some lubrication and can I do that myself?

[Alex645]

Now, the question is...can I get it repaired anywhere? Or does it just need some lubrication and can I do that myself?

@aslyfox mentioned in an earlier post getting their zoom fixed at:
Phototronic
119 NE US Highway 24
Topeka KS 66608
785 233 0231

Read more at: Pentax Repair Facilities (Wordwide listing) - Page 8 - PentaxForums.com

My hunch is that unless it's a one person operation like Eric Hendrickson, most shops are temporarily closed due to the Covid-19 situation. Unless you have the tools and experience, I would NOT try a YouTube repair. Zooms are trickier than primes....but hopefully a PF member has been there, done that, and can advise you otherwise.

[aslyfox]

@aslyfox mentioned in an earlier post getting their zoom fixed at:
Phototronic
119 NE US Highway 24
Topeka KS 66608
785 233 0231

Read more at: Pentax Repair Facilities (Wordwide listing) - Page 8 - PentaxForums.com

My hunch is that unless it's a one person operation like Eric Hendrickson, most shops are temporarily closed due to the Covid-19 situation. Unless you have the tools and experience, I would NOT try a YouTube repair. Zooms are trickier than primes....but hopefully a PF member has been there, done that, and can advise you otherwise.

he is a one man shop

call to check if he is open

[barondla]

I just started noticing some exposure issues with my 645Z where despite having the exact same camera settings, the exposure varies widely from image to image. For example, let's say I'm shooting at 1/60 sec, f/8, ISO 100...I don't change any settings, but from image to image the exposure varies widely.

So far it only seems to do this when using my 645-FA 150-300mm, so I'm hoping it's an issue with the lens (this wouldn't surprise me as I dropped it a while back and cracked the lens hood) and not the camera.

Any ideas on troubleshooting this?

As already mentioned it is probably a sticky aperture and will require service. It also wouldn't hurt to wipe the body and lens contacts clean. I've seen dirty contacts cause problems. Good luck.
Thanks,
barondla