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03-02-2017, 01:16 AM   #1
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Pentax MX SA-1 vs SA-3 focusing screen for f/1.4 Lens?

My MX has an SA-1 (01 on the tab), I'm wondering if using my Pentax-M 50/1.4 and Rokinon 85/1.4 would benefit more from the SA-3 screen which states it's specifically designed for lens with widest aperture between f/1.2 to f/2. (the only other lens I have for Pentax mount is a Tamron SP Adaptall 90mm f/2.8 1:1 Macro, and Pentax-M 28/3.5, the latter I probably won't use as much, and wouldn't need as critical a focus).

I was curious about it because it seemed easy to pop down the focus screen (much like on my old Pentax K10D digital SLR I used to have) to blow out some dust, and also did that so I could make sure the screen was correctly seated (I imagine if it was incorrectly seated, the focus would be quite a bit off even for f/2 in the resulting negative).

Pricing online seemed to be around 20 to 50 for various screens, I just haven't found a SA-3, just wondering if it'd be worth my while to keep an eye out for it.

03-02-2017, 01:39 AM   #2
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I haven't thought of that. I don't have an MX, but an LX with an SC-21 screen. I found it quite demanding to focus with the M 50/1.4, but thought it was nothing I could do about it. Maybe I should look for an SA-23?
03-02-2017, 02:05 AM   #3
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QuoteOriginally posted by deus ursus Quote
I haven't thought of that. I don't have an MX, but an LX with an SC-21 screen. I found it quite demanding to focus with the M 50/1.4, but thought it was nothing I could do about it. Maybe I should look for an SA-23?
Yea, not sure what your definition of demanding is, the MX I have was fully CLA'd in november, and it came with a 28/3.5 from the seller. I don't know if the repair person (receipt shows Eric Hendrickson as the person doing the work) checks against their own high speed lens, or if it's basically just a collimator (sp) to the focus screen.

I would have to do another test to be sure, but for example, close up at f/1.4, I could have sworn I focused on the toy robot, but it seems like the camera in front of it was focused. There were other shots at a distance indoors at f/2 (and some f/1.4) where the point of focus seemed 'soft', but it wasn't any sharper closer in front (and the wall would be behind it, so no way to know if the lens is just softer on film than adapted on my digital, or if the focusing screen isn't critical enough for 1.4) But course it was a handheld shot, the only way I can be sure for certain is to tripod it, especially since 1/60th with a 50mm approaches the bare minimum to handhold an SLR (I'm used to mirrorless and rangefinders which don't have a mirror slap). But I also wonder if I changed my distance slightly when I metered, moved the camera way from my eye, changing settings, and then recomposing without refocusing.

From my past experience the split in the middle is usually sufficient enough for f/1.4, it's the microprism ring that could be a little harder to discern (more so as the lens gets slower, but I guess there might be a point where precision becomes harder to pinpoint when the lens gets faster?)




Though these two seemed spot on, though I can't remember if it was f/1.4 or f/2, I know for sure it wasn't over f/2, I think on the smokey artwork, I had it at f/1.4 because I bumped the shutter up to 1/125 to make it easier to handhold. On the first one I focused for the edge of the artwork (and not the plaque), so that might have been 1.4 as well. The second I focused on the slit down the middle.





PS: You can use the MX and LX screens interchangeably, from what I read using an LX screen in an MX does affect the meter reading slightly, but an MX screen in an LX doesn't affect it (apparently metering isn't reliant thru the screen on the LX).
03-02-2017, 02:53 AM   #4
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Yeah, the LX meters off the film plane, so neither the screen nor the viewfinder affects the metering. To me it was the shallow DOF that made the focusing demanding. Maybe it doesn't come down to the focusing screen, but it would be interesting to find out.

Now I've gone digital, and the LX hasn't been used for a while. I have a dream, though, that I some day can make myself a darkroom and develop some film myself. Until then, I won't be looking very actively for accessories for the LX.

03-02-2017, 03:24 AM   #5
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:P You could always send me your LX...

By the way if you're curious, the rest of the scans of Tri-X off the MX earlier here in this Imgur Album.

Pentax MX + Pentax-M 50/1.4 & 28/3.5 + Kodak Tri-X - Album on Imgur
03-02-2017, 09:46 AM   #6
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QuoteOriginally posted by kb244 Quote
:P You could always send me your LX...
Ha ha, nice try! :-D

Those shots look great. Is that Tri-X really that grainy, or have you pushed the film?
03-02-2017, 09:56 AM   #7
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If I pushed the film, it couldn't have been by much, because even if I take into account the mishap in setting 640 on the internal meter, the development times I followed here for what was intended to be 400, his isn't as grainy, but I may be producing more in scanning the negs with underexposed shadows. (I might be slightly thinner than what his negs were)

FilmDev | jeielef's recipe | Kodak Tri-X 400 in Ilford Microphen stock

But here's the same dev time (with just a little more agitation) where someone rated it at 320 (medium format though, so much larger negative).

http://filmdev.org/recipe/show/11197

I've found that Tri-X tends to have a 'sharper' grain than most other 400 speed films depending on how it's developed. Not necessarily grainier, but sharper than say HP5+. Even in HC-110 (Which would produce a softer grain pattern), Tri-X next to HP5+, Tri-X is going to be noticeably crisper on the grain shape (and probably more contrasty). But that's one of the reasons I like Tri-X over HP5+.

Arista EDU Ultra 200 (aka Foma 200) however has more grain at 200, but it's an older looking tabular style grain, the only problem I have is the quality control (emulsion is either more delicate or they come pre scratched sometimes).

This is on AEU 200 in Microphen 1:3 (from my understanding a higher dilution tends to make the negative have more contrast, AUE200 develops too quickly in HC-110 to really be usable for me, at around 3.5 minutes for dilution B).



Edit The roll I have came from my professor, it expired late last year. I don't know the condition he stored it in, but it could account for the grain if it seems way more than anticipated. But usually a couple months past expiration shouldn't be an issue, especially as I deal with stuff that's been expired over 10+ years.


Last edited by kb244; 03-02-2017 at 10:04 AM.
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