Focusing Screen #42217 and #42170

[ian_kie]

what's the difference between #42217 and #42170?

I know #42217 is a D type screen,but what does "D" mean?

and which one is brighter ?

 

I've heard people said that #42170 is brighter but bit lower contrast.

but how come the older one to be brighter? o_Oa

 

thanks a lot .

[q.g._de_bakker]

Both screens are equally bright.<br><br>The "D" screen is a bit more like the old, pre-Acute Matte, diffusing screens, i.e. easier to focus, and better suited to judge the appearance of the out of focus parts of the image.<br>But only a bit.<br><br>The trouble with the Acute Matte screens, both non-"D" and "D", is that they use micro-lenses to project light towards your eye, in stead of scattering it in all directions, like the old screens do.<br>These microlenses do not project an image in a definite plane, but allow your eyes to focus on the image they produce, even if that does not coincide with the plane of the screen. In other words: you can see the viewfinder image being sharp, even when it is not.<br>The old diffusing/scattering screens had no such problem: the depth of the image they present is euqal to the depth of the rough, scattering surface. And that's not much.<br><br>So though much brighter than diffusing screens, the Acute Matte screens are harder to focus accurately. The "D"-screens are a first attempt to correct that: the screen was roughened more, so it scatters more. It helped only a very tiny bit.<br>SO the next thing that was done was to change the "standard" screen, the one you get when you buy a new camera, from a plain one to one with a split image rangefinder. And that indeed helps!<br><br>The contrast mentioned probably is the one between in focus and out of focus parts of the image. Or if they did not mean that, they should have.<br>A side effect of the optical trick the Acute Matte screens perform is that the bits that are not in focus are rendered rather differently from how the sharp bits appear. So it is easier to see what is and what is not in focus (though harder to get the in focus bits truly in focus). But what's also very important about this, is that the out of focus bits also appear very much different as they do appear both on diffusing screens and on film. You cannot judge how the final image will look like when using an Acute Matte screen as well as when using the older screens!<br>Making the "D" screens more diffusing helps to change that too, but again only a bit. So "D screens - like the old diffusing screens, but not nearly as much - have a lower "in focus - out of focus" contrast.<br>The contrast in terms of brightness is not much different, no matter what screen you use.

[james_brand]

Interesting. I have a hard time focusing with my D screen. I thought it was me. I prefer the split microprism screen that I have now. My eyes work better with the microprism.

 

Are the older screens interchangable with the new ones? They are so cheap, I may want to try a non Accute Matte screen for kicks.

[q.g._de_bakker]

They indeed are: older screens and newer, Acute Matte screens, all fit alike.<br>The only thing to remember is that when using a metered prism finder, you need to adjust according to what screen is used and with what finder, with the older screens being 1 stop less bright.<br><br>The old standard screen is perfectly fine, a bit less so when light levels get low. And the Fresnel lens of these old screens is rather coarse, very visible lines. But that doesn't interfere with either focusing or judging the image as a whole.

[jenny_jaques]

Photographing at a seaside location recently, I was glad I'd kept the old standard screen in the kit bag. It was much easier on the eyes than the Acute Matte screen.

 

I'm glad of the Acute Matte when inside doing table-top photography, especially with slower lenses like the f5.6 S-Planar 120mm. But even then, I will often take off the magazine and fit the early Viewing Screen adapter (which has a standard screen) with chimney finder. (This set-up also gets round the mirror cut-off) Even when stopping down to the working aperture, the old standard screen with chimney finder is very user-friendly. Just as important is the ability to adjust the ocular on the chimney finder, fine-tuning it to suit my eyesite. Once I can see those great big chunky Fresnel rings and all the dust on the screen, I then look at the image.

[ian_kie]

Thanks a lot , these information are really helpful .

[jenny_jaques]

You're very welcome Ian.

 

(Isn't it nice when people come back and acknowledge with gratitute the help that is offered?)