[Popty Ping]

Hi all

Firstly - I’m not sure this is strictly troubleshooting, more an observation and plea for information!

I have a K-r and it’s fine for my needs. I use it to shoot music events for friends and enjoy that very much.

I feel that the thing holding my back is the dark viewfinder and the difficulty focus in the low light.

I have tried a few things I hoped would help. These include:

- using Live View (I’m not too keen on it, as there seems to be a “lag” before the photo is taken and it drains the battery. I just like having the camera to my eye

- getting a replacement viewfinder with a bigger field of view (I can’t remember it’s name now)

- using lenses with a wide aperture e.g Sigma f1.4. My understanding is the view you see is that when lens is wide open. I could well be wrong on that though.

I guess I’m asking if there are any solutions to this I’ve not tried.

At some point, I may upgrade - are there Pentax models where the brightness of the viewfinder is significantly better?

Thanks for reading - at some point I hope to be good enough to answer questions on here, as opposed to just asking them!


Si

[UncleVanya]

The k-r has a pentamirror rather than a pentaprism. The latter is much brighter.

The k-r is also write a bit older and the af in low light has improved over time. A faster lens like the 24 1.4 may appear brighter, but that generation camera may struggle to focus it reliably. Focus sensors aren't typically calibrated for f1.4 and can miss critical focus. Newer cameras have more efficient live view as well.

What lenses do you have?

---------- Post added 04-29-18 at 09:50 AM ----------

Oh and I don't know of any replacement viewfinder.i think you may mean focusing screen. Katzeye made an optibrite screen but they are out of business.

[Popty Ping]

Thanks for the reply.

Interesting about the Pentamirror/pentaprism - I wasn't aware of that.

I just have the 18-55 kit lens, the Sigma 18-250 travel zoom, Sigma 31mm f1.4 and a couple of old Pentax film 50mm primes (given to me by a kind PF member)!

Sorry, I get my terms mixed up sometimes - still pretty new to photography. I just meant something that could be used instead/in addition to the normal viewfinder. I have a vague recollection where I'd seen cameras where they could be added to the camera somehow to give a better, brighter display than the one usually used. I could be really wrong on that though!

Thanks again.

[UncleVanya]

There is a magnifying eyepiece that can help with critical focus, but that doesn't increase brightness. The katzeye optibrite focusing screens did increase brightness. There may be some available used. As for your lenses. Those zooms are likely much darker than the primes. You can get faster lenses or a more updated body - the updated body with pentaprism will be brighter with every lens but faster lenses might be brighter still I can't say.

When you use the f1.4 lens is it significantly brighter?

[Just1MoreDave]

What you see through the viewfinder is the surface of the focus screen. The lens projects an image onto the mirror which bounces it up to the focus screen. The focus screen surface is etched - if it was perfectly smooth, it wouldn't work. Like everything else in photography, this etching is a compromise which works best for certain lenses and not so great for other lenses.

A typical lens is wide open when you look through the viewfinder, at whatever its maximum aperture is. (It doesn't matter what aperture the camera is set to, just the maximum aperture.) Say you are using an f1.4 lens. When you take a photo, you know that f1.4 lets through twice the light as f2.8, 4x the light of f5.6, and so on. So you expect to see the same thing through the viewfinder: the f1.4 lens should make the viewfinder really bright. That doesn't happen because of that compromise etching. The stock screen stops getting brighter around f4 or so. This is hard to demonstrate unless you use an M42 screwmount lens. With that lens, turn the aperture ring to f8 and the viewfinder is dark. Keep opening up the aperture and you'll see a point where the screen doesn't get brighter any more.

The stock screen is optimized for f4 to f5.6 brightness. This works great when you use inexpensive zoom lenses, which are exactly that brightness. There are focus screens optimized for brighter lenses like your f1.4, and those screens will show a brighter image in the above test. But the inexpensive zoom lenses will have a darker viewfinder.

Pentax uses pentaprisms now, so anything newer than the K-r will show a slightly brighter viewfinder because of that. The real problem is the focus screen, which will be similar in any newer DSLR. Live view skips the focus screen, but I don't actually know how that works because I don't use it either.

[Popty Ping]

Thanks so much for all the replies folks.

I didn't find the f1.4 Sigma lens significantly brighter to look through. I was a little disappointed about that.

Didn't know that about the focusing screen surface - I learn loads on here! I do now have an external flash with an AF assist beam - I think it would be a bit intrusive to use that at events I go to though.

Plenty to think about - thanks again.



Si

[mikesbike]

For the last 5 years or so, Pentax has been the only brand of DSLR, all of whose whose models, regardless of price, feature the more expensive glass pentaprism viewfinders. They also show 100% of the framing you will actually get in your picture. This type of VF is of professional standards. It doesn't get any better, regardless of cost, in the APS-C size sensor. So as it is currently, whether you buy a K-70 or whether you buy a KP, the VF will be of the same quality. Once you get a better VF, you would then likely notice the further improvement in brightness between a lens of f/3.5-6.3 and one of f/1.4 or so.

When in a dark environment, set your camera for center-only spot focus and choose something in the scene having more light on it that is of the same distance of that you wish to train your focus on, even though the better-lit subject itself is not centered right for your shot, then once you focus on that by using the half-press, continue holding that focus with the half-press while you re-position your camera to get the shot you are after, then complete the shutter button press to fire your shot.

The AF assist beam is only good for fairly short distances.

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Last edited by mikesbike; 04-30-2018 at 12:17 PM.

[UncleVanya]

Honestly I'd be looking for a new camera body - since the ISO performance has dramatically improved and the viewfinder is better and the AF is better. No need to get the latest if that is out of reach. Keep the K-r as a backup and buy a K-50 or a K-5ii or even a K-30 for that matter.

[Popty Ping]

Thanks for the latest advice guys.

Mike - I hadn’t thought of that technique.

Uncle - I’ll think about upgrading. It’s probably not possible money-wise though in the nearish future.

[UncleVanya]

Thanks for the latest advice guys.

Mike - I hadn’t thought of that technique.

Uncle - I’ll think about upgrading. It’s probably not possible money-wise though in the nearish future.

Let us know if the technique works for you. If it doesn't I think a body upgrade will cost less and have more direct impact than lens changes. But using what you have is the cheapest option if you can get what you need from it