Focusing Screens

There are two things there johnriley. Firstly it's nothing to do with eyesight, secondly you obviously missed my mention of "using a standard Pentax focussing screen"

Actually 'we' can see more DOF than actually exists. Indeed this is the problem. As Algi and I keep trying to explain, the DOF shown in the viewfinder is greater than actually exists in reality.

This is easily proven by looking through the viewfinder, taking a picture at 1.2 and comparing the DOF.

Nothing to do with 'nomenclature'

And where is this Pentax screen that is designed for 1.2 or 1.4 ?

Pentax Lenses and Accessories, 9/87, page 77.

And in that article he actually mentions that canon do make a screen for lenses great than 2.8

http://www.kenrockwell.com/canon/slrs/5d/focus-screens.htm

And that's where the EE-S screen is recommended and of course why the Pentax Community has also recommended a cut down version of the EE-S screen and a company even cuts them down to order for people not confident enough to do it themselves

Link?

I just looked on the official Pentax Site and couldn't find any such thing.

http://www.pentax.co.uk/en/viewfinder-focusing-screen.html

'9/87' ?? Are you sure you're not referring people to a dinosaur product that's not available any more?

I am referring you to the items that were contemporary with the lenses themselves. And I'm suggesting that it might be a good idea to use these screens if its possible to adapt them.

They are no more dinosaur than the lenses as they were provided at the time. The lenses too are not available any more. 9/87 refers to the copy of the book that I happen to have in front of me. This means September 1987 and there are both earlier and later editions.

As for what people want to do, that is entirely up to them and I'm sure they have all the information now in this thread and others that they need.

While a pentax 1.2 lens isn't available new anymore there are wide aperture lenses that are currently available ( all on SRS Website )

Pentax smc FA 50mm f1.4 Lens
Pentax smc DA* 55mm F1.4 SDM Lens
Pentax smc FA 31mm F1.8 AL Limited Lens


The Canon EE-S Screen is available now. A company will cut it down to order. Trying to source a Pentax Accessory that was available in 1987 may not be completely impossible, but I would imagine would be little better than a wild goose chase. It might be uncomfortable but sometimes a non-Pentax product is the best solution.

In theory what you see through the viewfinder is Lifesize and has nothing to do with 36x24mm. In practise with the K-5 what you see is 92% of Lifesize. The apparent distance in theory would be at infinity, but because that means using the eye muscles to focus most manufactures set it optically at about 1M. The big selling point about the OM-1 used to be that it had a big viewfinder, but they had actually moved the apparent image closer to the eye which made it very hard to see the full viewfinder.

With the old ground glass camera screens... coarse ground ones snapped in and out of focus better than smooth ground, but you couldn't see as much small detail.

That's the correct one for actually focusing using the microprism, but it may not work with DOF, although I would expect older screens to work better than modern ones. The original Nikon F screens were ground glass and should work, but probably wont fit Pentax K-5's

Having read all the threads in the other place about focusing screens I was hoping for a further reasoned debate in this house. Some pertinent comments have been raised thus far, as have some others that have indirectly led me towards a greater understanding of my enduring problem. Namely capturing acceptable (to me) sharp manually focused images in low light situations. For myself I found that fitting the Tenpa type magnifier with the flat eye-cup and keeping my glasses on while focusing produced a marginal improvement in matters. However the great leap forward towards acuity (or backwards if that's your focus problem) came when I plucked up the courage to remove the GX20's focusing screen and experiment with shimming it. The DOF I am seeing in the viewfinder using the 50mm f1.7 is now much closer to what I am seeing up on my screen.

It seems to me that the standard focus screen ain't that bad but it ain't that good either (try shimming it :wink. I'd like to try something different and the Canon substitute looks promising, but I have read that it is no good in low light and I baulk at paying more for a screen than I would for any of the lenses I can afford. Especially if it leads to no further improvement in my affliction. I've not read anything positive about the cheap Chinese screens, are they really worse than what came with the old 35mm SLR's? If not I could live with that.

Meanwhile as I watch this discussion develop, I'll try further experiments with my manual focusing technique and hope that at some point in the not to distant future I'll crack it, or Pentax Ricoh comes up with a solution to my vexing problem. Perhaps an upgrade to the next big thing might improve matters?

Some one correct me if I'm wrong, but I was always under the impression that shimming the focuss screen was to ensure it's lightpath distance was exactyl the same as teh distance to the sensor, for focus accuracy, and not for altering the perceived DOF.

You are quite correct Smeggypants.

I don't have a f/1.2 lens, but I can focus my SMC-A 50mm f/1.7 quite accurately fully open using the KatzEye screen. My main reason for buying a KatzEye was that I was using a 300mm zoom, sometimes fully open at the long end, and had problems focusing manually - plus having grown up with an old fully manual film SLR I expect to see a split prism when I look through the viewfinder!

Has anyone tried a KatzEye screen at f/1.2, and does it work?

I cut down an ME split prism for my K100D years ago and loved how useful it was. Only downside apart from metering and disc blackout ( which never bothered me) was the scaled up view of the disc diameter. Had a squiz through my ME super and was surprised how much smaller and less dominant the disc is.

I have modified a new Ee-s Canon screen for my K-5. Has no markings what so ever.
The extra pop with the K50/1.2 is obvious. Makes focus pretty certain but not convinced a small split disc wouldn't be better for me. My eyes aren't 100%.

Pete