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Forum: Pentax Medium Format
03-15-2023, 09:39 PM
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without clear coat，the brass will turn brown color after few month. I repolished it and add clear coat (gloss oil). It now hold the more golden color forever.
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Forum: Pentax Medium Format
04-23-2021, 07:42 AM
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Yes I fixed these problems with a shutter speed test device, a photodiode and an oscilloscope. I will write an article about that.
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Forum: Pentax Medium Format
02-26-2021, 02:59 AM
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Pentax 6*7 with MLU ___ high speed exposure issue
Hi friends,
I got a Pentax 6*7 with MLU, camera seems fine except exposure at high speed(1/1000 1/500 1/250 1/125)
At shutter speed of 1/1000 and 1/500 sec, the curtain did not open for >90% of the times
At shutter speed of 1/250 and 1/125 sec, I got uneven exposure from left to right. (see picture)
I already disassemble most of the camera covers, did anybody know how to fix this problem?
tension of the curtains problem? Electromagnet problem? lubrication problem?
I have a shutter speed meter with enough accuracy, also some comment tool and lubricant.
Could anyone give me some suggestion?
Thanks!
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Forum: Maintenance and Repair Articles
02-24-2021, 02:53 AM
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Hi Aristotle，
Very impressive job!
I have 6*7 with MLU, but the shutter curtain did not always open at 1/1000 and 1/500 (most time unopen, few times open). lower shutter speed seems OK. do you know what may be wrong? i already open the camera cover but did not disassemble the mechanics. could you give some advise?
Thanks!
Jie
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Forum: Monthly Photo Contests
01-01-2021, 07:55 AM
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hopping bird
SMC Pentax-DA* 300mm F4
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Forum: Post Your Photos!
01-01-2021, 07:48 AM
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Forum: Pentax Medium Format
06-23-2020, 09:33 PM
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Hi jimpurcell，
it takes about 5 hour to do the sandpaper work and hand-hold motor-spin polish.
better take the metal piece apart from the pentaprism. use lacquer diluent will make it easier
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Forum: Pentax Medium Format
06-23-2020, 06:50 PM
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Hi wa2kqy，
I use sandpaper to clean the black paint. and a hand-hold electric polish tool to polish the brass.
the logo is painted with a gold-color oil pen
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Forum: Pentax Medium Format
06-23-2020, 08:27 AM
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End up play with the camera body rather than taking photos....
Do you guys think it looks cooler?
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Forum: Film Processing, Scanning, and Darkroom
05-16-2020, 04:51 PM
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Thanks guys~
Finally get it to work with method in test #5.
here is a new roll with reversal process.
some image have flaw (black dots), is it defect of the film itself or film go mouldy or my chemicals have impurities?
thanks!
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Forum: Film Processing, Scanning, and Darkroom
05-14-2020, 07:37 AM
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Hi tuco, I do light re-expose by taking film out of reels.
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Forum: Film Processing, Scanning, and Darkroom
05-14-2020, 06:01 AM
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this is the image I used for test # 3-7
-2 -1 0 +1 +2 means under/over expose by 1/4 , 1/2 , 1 ,2 , 4 times the camera expose time.
I use pentax KX with 50mm lens @ F1.7 and 1/125 sec for normal expose. film iso 200 .
---------- Post added 05-14-20 at 06:51 AM ----------
Thanks Alex, i updated the image so you guys can have a better idea.
i agree with you that the problem is from agitation, and i am quite sure it is in bleach step.
so far I get a reproducible reverse process which suit my film and equipment, and it works without major fault.
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Forum: Film Processing, Scanning, and Darkroom
05-14-2020, 05:41 AM
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here is the result for test #3-7
I guess the fogging issue is most likely the agitation in bleach step.
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Forum: Film Processing, Scanning, and Darkroom
05-14-2020, 01:28 AM
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Thanks guys, here is an update with more tests (Alex maybe interested, I will update the image soon)
After 5 more test (test #3-7)，I think the problem is from agitation. But I cannot tell it is bleach or first development issue.
Here is how I redo the test. A little long in text.
---------------------------------
test #3 conventional negative process
step 0 wash the Anti-glare
Developer ( Kodak D76 for 7 minutes: 1 minute rotation + every 10 sec rotation in 60 sec.)
Stop CB-1
Fix F5
Get OK result (first time trying negative process, hahaha… )
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From test #1 and #2, I thought the middle fogging may cause by small film separation and the chemical (in between the films) get depleted locally. I guess this is why agitation is needed in both development or bleach.
Then I reduce the film length so that there is only one full circle warping film ( without concentric overlap). but in test #4, the fogging pattern still appear everywhere in the middle. so the problem is more likely caused by horizontal movement (rotation most likely ?). So, in test #5, I avoid all rotation movement by not agitating in first development combined with non-rotation in the bleach process.
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test #4: B&W reversal process (failure)
step 0 wash the Anti-glare
step 1 First developer (Kodak D72 + adding 1g potassium rhodanate) ( 4 minutes: 1 minute rotation + every 10 sec rotation+ 5 second figure eight in every 60 sec.)
step 3 Bleach (5 minutes: continue rotation + figure eight.)
---Right after bleach, I re-open the bottle in light for wash (in step 4) , I saw the yellow milky pattern in the middle of film (in step 4) which become the grey fogging after second development. so the fogging problem is from step 1-4.
---feel bad but continue process anyway----
step 5 Sodium Metabisulfite clean bath ( 5 minutes: continue rotation + figure eight.)
step 9 second develop D72
unmentioned steps are same as test #1 #2.
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test #5: B&W reversal process (with success)
step 0 wash the Anti-glare
step 1_First developer (Kodak D72 + adding 1g potassium rhodanate) ( 4 minutes: complete still, no agitation except first-3-sec knock-off bubble) ( I see a YouTube video saying agitation only affect contrast in first development)
step 3_Bleach ( 5 minutes: open bottle in dark room. Pour in bleach liquid and continue agitation by Immerse and lift up（lift up 2cm, still submerged in the bleach liquid）and re-immerse the reel only in vertical direction)
I change to this agitation method to avoid any horizontal movement
setp 4-5-6 in darkness.
step 5 Sodium Metabisulfite clean bath
step 7 re-expose: no fogging pattern in the middle.
step 9 second develop D72
unmentioned steps are same as test #1 #2.
test #6: B&W reversal process (failure with known reason)
step 0 wash the Anti-glare
step 1_First developer (Kodak D72 + adding 1g potassium rhodanate) ( complete still, no agitation)
step 3_Bleach ( 5 minutes: complete still, no agitation）
I change Bleach without agitation to see if agitation is necessary for bleach (answer is YES!)
setp 4-5-6 in darkness.
step 5 Sodium Metabisulfite clean bath
step 7 re-expose (see image)
step 9 second develop D72
unmentioned steps are same as test #1 #2.
comments： inadequate agitation in bleach-step lead to an unwashed camera-exposed image.
test #7 all the same as test #5 to see if the result is repeatable. (YES! successful)
Conclusion：
The fog issue could come from 3 place based on my test:
1. First develop agitation (could be rotation since there is not figure-eight in test#1 and #2)
Personally, I did not think it is First develop agitation issue because the test#3 for negative develop is OK. And there is a lot of people using this type of reel.
2. bleach agitation (could be rotation since there is no figure-eight movement in test#1 and #2) most likely
3. early expose to light in step 4 (wash)
I guess I could do one more test to narrow down this fog problem:
First develop non-agitation + rotation bleach agitation. If fog show up. Must be bleach agitation issue
updated image below
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Forum: Film Processing, Scanning, and Darkroom
05-10-2020, 07:16 AM
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Hi guys,
I come across some fog issue when i develop my first B&W film.
I pick the reversal process because I can see the positive picture on film.
The exposure should be right since my KX camera (with light meter) works well on color negative film developed by a professional shop.
I pick FOMAPAN 100 negative ( NOT FOMAPAN 100 R). and kodak D67 for first development (7:30 first try. 5:30 second try), I reduce the development time and the agitation frequency for my second try because the contrast on first try is too high and the image also appear too light.
The end result for both all have fog issue. Even at the very beginning of the film (see the film head circled in the picture) .film head is full exposed to light at film install.
Could anyone tell me which step is wrong?
I guess the development process or the bleach process is not enough.
Thanks !!
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Forum: Pentax SLR Lens Discussion
04-18-2020, 09:21 PM
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Hi Guys,
I broken few screw (stripped screw) when trying to open a Pentax DA lens.
does anyone know the type of the screw so that I can buy some replacement one?
I guess the screws are of the same type for most DA lens. so is it metric or imperial ? what size ?
Thanks!
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Forum: Film SLRs and Compact Film Cameras
04-18-2020, 07:07 PM
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I take the focusscreen out and put it back ( need to remove the pentaprism), not destructively. You can clean all the dust by doing this.
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Forum: Film SLRs and Compact Film Cameras
04-18-2020, 05:21 AM
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I recently take apart an broken Pentax M42 Spotmatic for decoration.
Fun to see the inside...
Did not fully take it apart because that will be messy.
Leave your e-mail below if you want to DIY using this background with annotation and picture for reference.
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Forum: Monthly Photo Contests
04-04-2020, 06:09 AM
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I would like to nominate this photo
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Forum: Monthly Photo Contests
04-04-2020, 06:08 AM
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I would like to nominate this photo
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Forum: Winners' Showcase
04-04-2020, 06:07 AM
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I would like to nominate this photo
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Forum: Monthly Photo Contests
04-04-2020, 06:06 AM
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I would like to nominate this photo
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