I recently got a Pentax 645n and have been playing around with it. I have noticed I am unable to change the ISO by pressing the buttons on the right, even with the dial on the left turned to the ISO option. It’s just stuck on ISO 100. I’m hoping there’s something super easy I’m missing.
When you say the dial on the left is at the ISO position, are you holding the small lever on the side of it pushed up so the pointer is straight at ISO? The lever itself doesn't quite show in your photo - it's on the outer side of the dial, near the front.
You’ll need to slide and hold the Auto bracketing selector on the Exposure compensation dial to the ISO position - while holding the Auto Bracketing selector depress the up / down buttons.
No problem! We're happy to help. And I LOVE my P645N and have the manual (obviously). If you have any other questions about it, just ask. For me, it's a simple camera, but it wasn't my first film camera.
pentax brings back alot of nice memories - starting with the pentax spotmatic (35mm) and last used a pentax 645 for about 15 years. very nice camera, workmanship, pictures.