[stillshot2]

I am just wondering why Pentax puts matte focusing screens in their DSLR's, such as what I have in my K30? Are there any benefits to having one as opposed to a regular clear viewfinder? I find it does not help me manual focus any better than my old Sony DSLR that did not have a matte focusing screen, so I would like to know if there is a certain technique to using a matte screen?

[elliott]

I've never seen a completely clear focusing screen in any SLR, I don't see how you'd be able to focus with one.

Which Sony did you have?

[stillshot2]

It was a Sony a330 with a small pentamirror viewfinder. By clear I mean that the images I saw through the viewfinder didn't have a grain-like texture to them like I noticed the first time I used the K30. I sold the a330 before I bought my K30, but I definitely remember the a330 was as clear as looking at a mirror and I focused it by going off what looked best to my eye. I feel this texture on the K30 doesn't make things any easier, so that's why I am wondering if there is something more to the K30's screen that I am not understanding? Or is this more of a property of having a larger pentaprism viewfinder?

[maxfield_photo]

I don't think Pentax does put a matte focusing screen in their cameras as a stock option. I have an older K20d and I've replaced the stock screen with a Katzeye. Even without the split prism and microprism collar, I can notice a big difference between the rendition of the matte Katzeye and the stock Pentax screen. It may be that Pentax's screen is just less shiny than the Sony screen.

[stevebrot]

I am just wondering why Pentax puts matte focusing screens in their DSLR's, such as what I have in my K30? Are there any benefits to having one as opposed to a regular clear viewfinder?

Define "regular clear viewfinder". A fine-grained Fresnel field such as the one in your K-30 has been pretty much the standard in SLR cameras for a long time (several decades). There are better screens available from a manual focus standpoint, but I don't know that any are clearer.


Steve

[stillshot2]

By clear I mean that the images I saw through the viewfinder didn't have a grain-like texture to them like I noticed the first time I used the K30.

Such as looking at the sky through my Sony a330 just looked exactly like the sky, not a blue background with a luster type photo print look to it like the K30 does. That's the best I can explain it. As far as I can remember DSLR cameras I have tried from other brands did not have this noticeable effect either. My Canon AE-1 with it's huge pentaprism a grainy effect too, but it also has a split prism focusing screen, which is why I am guessing this is a property of a focusing screen more than the actually prism or mirror?

[stevebrot]

I have used both the K-30 and K-50 and would not characterize either display as grainy. Part of what you are experiencing may be due to the Sony only having 0.74x magnification vs. the K-30 0.92x magnification. Translation? The viewfinder image for your K-30 is 24% larger which may mean that you are able to see the graininess that is there on the Sony, but invisible due to small size. Just a thought.

My Canon AE-1 with it's huge pentaprism a grainy effect too, but it also has a split prism focusing screen, which is why I am guessing this is a property of a focusing screen more than the actually prism or mirror?

Well, there you go. The AE-1 had about 95% frame coverage and 1:0.86 magnification making for a huge viewfinder image with a bit more magnification than the K-30. If you had complaints about graininess of the AE-1, I can see why you are seeing the same thing on the K-30. As for the split-image...yes, that is a feature that is built into the focus screen. Your K-30 will accept aftermarket screens having a similar split image (I use the Katz Eye in my K10D), but it will probably still appear grainy to you. There are trade-offs and cautions, but if you frequently use manual focus lenses and want to use the viewfinder for focus, an aftermarket screen is a strong recommendation.


Steve

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Last edited by stevebrot; 03-26-2014 at 07:31 PM.

[elliott]

I think I can see the difference you're talking about when I look through my K100D and K-5, granted neither have their original screens (Chinese split in the K100D and Canon Ee-S in the K-5). It must be down to magnification of the viewfinder, the only difference mirror vs prism should make is brightness. The big viewfinder with high magnification is allowing you to see more detail of your shot, but also the detail of the screen itself.

[stillshot2]

I just looked through a Nikon D7100 viewfinder at a local store today and it has the same size pentaprism viewfinder as the K30 but was crystal clear sharp without the grainy-like appearance. Wish the K30 was like that

[AquaDome]

Did you purchase your K-30 used? Maybe someone put a matte screen in it?

[Imageman]

I think I understand this.


Some history first to put it in perspective


Originally focussing screens were a sheet of ground glass, these were fitted to plate, 5x4, and 6x6 cameras. The reason is the lens would focus an image on it and you could see and focus correctly. All screens were dark and awkward to focus well.


35mm screens were ground glass or plastic, dim and awkward to focus in marginal light but the appearance of focussing aids like microprisms and split screens helped with focussing, Fresnel screens helped in brightening the image in marginal conditions for composing.


Focussing screens were all relatively dark and grainy looking.


With autofocus the camera focussed without help from the photographer and traditional matt ground glass or Fresnel interfered with the cameras autofocus sensors so clear glass was adopted for screens, the clear glass helped composing the image in poor light, they were much brighter, but they were useless for focussing the image so manual focussing had to be abandoned.


Manufacturers found however that some matting was helpful in depth of field perception and in manual focussing for those photographers who complained the new screens were unhelpful in these areas. All adopted their own version of matt typically just enough to not affect the autofocus.


So today different camera bodies have different screens with different amounts of matting, therefore some will appear more grainy than others, and some appear like clear glass.


I think these are the differences the OP refers to.

[stillshot2]

Yes! These are the differences I am referring to. Might I also add that I have owned 2 K30's I bought used from KEH, and both looked the same way (the first one was replaced under a warranty with a different one). I personally felt it was easier to manual focus with the D7100 in the store, so what is the proper technique to use with a grainy screen that would help me focus better than a clear glass-like screen? (I mainly use manual focus when birding at 300mm when there are lots of tree branches so efficient manual focus is critical).

[lmd91343]

What most folks said here is right on. SLR focus screens are matte with a fresnel lens component in the screen or the condenser lens between the screen and the pentaprism. The matte surface is to aid in focus. The slight fresnel component is to make the VF image appear to have the same brightness across the field of view.

In the 1970s, Canon made some experimental focus screens for the F1 and F1n, 1st and 2nd generation models. I have two of those screens the "J" and the "Y". The have almost no fresnel component and a perfectly clear screen. They are for very low light use. Each one is optimized for a specific FL lens. They are hard to use in normal circumstances.

Here is a picture of them taken with my cell phone today:

[Imageman]

OK stillshot, this will be tough,


First the focussing screen must be at least slightly matt, no screen will be perfect but a clear screen cannot under any circumstances be used for manual focus.


Its still going to be hard but this is the method.


First you have to look through your viewfinder and set the dioptre so you see the most focussed and sharpest image of the marks on the screen, the autofocus marks. This is the most critical and will make the most difference.


Next, you must focus your lens on an object and then focus your eye on one of the autofocus marks on the screen, so your eye is focussed on that. This makes sure your eye is focussing on the screen surface and not slightly above or below it.


Then keeping looking at that autofocus mark bring the object in the viewfinder to focus, so both the autofocus mark and the object are focussed together. This aligns the focus.


Do this for 1 hour constantly, Then start taking test photographs, point focus shoot, point focus shoot. peep the pixels and check if you achieved focus successfully.


After 1 week of this you should be able to hit focus quickly and efficiently, you will still fail on low light and low contrast subjects, but you will achieve a high proportion of good focus.


Your target is to focus and shoot on 12 different subjects one after the other, and then after shooting all 12, peep the pixels and see if you hit focus on all 12. 11 is a fail.


Only when you hit all 12 and no missed focus should you take it to the field.


In the field set 2 f stops below wide open, then you will nail every focus, The occasional missed focus will be sharp due to the depth of field you dialled in. On critical subjects take 3 images refocusing after each, if you miss a focus the first time you nail it the second.


Birding will be awkward all I can suggest is practice and multiple exposures as I suggested above.


You don't mention the lens you use. If its a zoom, the focus ring will be a short travel ring, I recommend using a long travel ring, focussing is slower and more lengthy but will be more precise.

[maltfalc]

With autofocus the camera focussed without help from the photographer and traditional matt ground glass or Fresnel interfered with the cameras autofocus sensors so clear glass was adopted for screens, the clear glass helped composing the image in poor light, they were much brighter, but they were useless for focussing the image so manual focussing had to be abandoned.


Manufacturers found however that some matting was helpful in depth of field perception and in manual focussing for those photographers who complained the new screens were unhelpful in these areas. All adopted their own version of matt typically just enough to not affect the autofocus.

i don't know of a single slr that has the autofocus built into the viewfinder and that uses a clear screen. care to name one?