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10-13-2008, 10:24 AM   #1
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Jupiter-9 85mm and exposure

i use a Jupiter-9 85mm f2 (black version) on my K10D.
it is a M42 lens. i have original pentax adapter.

i use this lens in AV mode.

there is a strange situation:
when i use in f2, if i want to have a goode exposure i must put +1.3 EV
when i use in f2.8, if i want to have a good exposure i must put +1.0 EV
when i use in f8. if i want to have a good exposure i must put 0 EV

it is normal?

10-13-2008, 10:53 AM   #2
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This is quite normal. As with all M-42 lenses on the K10D, exposure with the Jupiter-9 is variable. The causes are poorly understood and the workarounds sort of clunky. Here has been my experience with the Jupiter-9 (newest version...MC black):
  • Upwards of 2-3 stops underexposed wide open in bright light. 1-2 stops under dimmer conditions.
  • 1 stop underexposed at f/4
  • Accurate metering at apertures at or narrower than f/5.6

My general practice with the Jupiter-9 is to use AV mode and chimp the histogram if I am using apertures wider than f/5.6. This technique is a little ponderous, but it is entirely in character with the ponderous nature of the J-9, in general .

Steve

P.S. Glad to see that you got your copy. Post some pics when you get a chance

Last edited by stevebrot; 10-13-2008 at 10:59 AM.
10-13-2008, 03:35 PM   #3
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really with all M-42 lenses on the K10D, exposure is variable?
i didn't know this info. thanks.

but at f2.0 i must put +EV and you must put -EV (underexposure)!!
why???
very strange!

P.S. do you want to see my jupiter or a photo made by jupiter?
10-13-2008, 03:48 PM   #4
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QuoteOriginally posted by platinum Quote
really with all M-42 lenses on the K10D, exposure is variable?
i didn't know this info. thanks.

but at f2.0 i must put +EV and you must put -EV (underexposure)!!
why???
very strange!

P.S. do you want to see my jupiter or a photo made by jupiter?
Sadly, the potential for strange metering exists for all lenses that lack the A-mount electrical contacts. The issue is documented in the user manual and in the lens compatibility matrix for the K10D, but not in a very clear way.

I put +EV compensation to correct substantial underexposure when full open. Sorry about the lack of clarity.

Yes, share your photos taken with your new lens! If you like, post a picture of the lens as well. We all like to see each others gear

Steve

10-13-2008, 06:05 PM   #5
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note the following from some time ago

https://www.pentaxforums.com/forums/241716-post69.html

There is another thread running today in the DSLR forum on K10D exposure with manual lenses.

The issue is the focusing screen, and what I suspect is off axis scatter impacting the metering sensors.

if you put an *istD screen into the K10D it meters great on manual lenses, but for each different maximum apature on "A" lenses it has a different error.
10-14-2008, 01:13 AM   #6
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QuoteOriginally posted by Lowell Goudge Quote
note the following from some time ago

https://www.pentaxforums.com/forums/241716-post69.html

There is another thread running today in the DSLR forum on K10D exposure with manual lenses.

The issue is the focusing screen, and what I suspect is off axis scatter impacting the metering sensors.

if you put an *istD screen into the K10D it meters great on manual lenses, but for each different maximum apature on "A" lenses it has a different error.
your words are interestings.
so the *istD focusing screen is important for manual lens on K10D.
about you if i use a *istD focusing screen on my K10D when i take photo by jupiter-9 m42, i will thake photos without exposure problems?
10-14-2008, 03:48 AM   #7
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QuoteOriginally posted by platinum Quote
your words are interestings.
so the *istD focusing screen is important for manual lens on K10D.
about you if i use a *istD focusing screen on my K10D when i take photo by jupiter-9 m42, i will thake photos without exposure problems?
this was the experience I had when I ran the test.

My experience with my *istD is that it always has metered well with manual apature lenses. My line up includes

24mm F2.5 tamron
50mm F1.4, M-100mm F4 macro, 105mm F2.8 135 mm F2.5, 300 mm F4 pentax
70-21- F3.5 Series 1 (Version 1) and 400 mm F5.6 Vivitar


when I ran the test, I only used one lens, but since the exposure as measured by the K10D was identical to the *istD, when the K10D had the *istD focusing screen installed, I can only assume that all other lenses would respond the same.

The real problem is that the K10D will have its metering with "A" lenses biased with the knowledge of maximum apature, and this is used to take out the problem introduced by the focusing screen. As a result, with an A lens, the K10D would have a metering error on any lens not at F4. It would, however be a constant exposure error but you would have to change the compensation each time, and unlike the *istD, on the K10D, you cannot set compensation to function in manual mode.
10-14-2008, 08:47 AM   #8
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see here a jpeg photo taken by my jupiter-9

iso 400
1/200
f4
+0.7 EV

i resized it



10-14-2008, 04:39 PM   #9
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Some people will probably be upset that I'm saying this, but my personal experience as a Pentax and Olympus system user is that Olympus DSLRs do a better job than Pentax DSLRs when it comes to consistently metering with old Pentax lenses.

I love my Pentax DSLRs and my Pentax DA and FA Limited primes (and Pentax DSLRs meter perfectly with these newer lenses) but when it comes to using old m42 screwmount glass or old manual K-mount lenses the Pentax DSLRs meter all over the place.

I've found that using spot metering with Pentax DSLRs and old lenses produces the most consistent results, but I now use m42 and Pentax K-mount adapters on my Olympus cameras whenever I want to use an old lens for a particular look.
10-15-2008, 04:16 AM   #10
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QuoteOriginally posted by JJJPhoto Quote
Some people will probably be upset that I'm saying this, but my personal experience as a Pentax and Olympus system user is that Olympus DSLRs do a better job than Pentax DSLRs when it comes to consistently metering with old Pentax lenses.

I love my Pentax DSLRs and my Pentax DA and FA Limited primes (and Pentax DSLRs meter perfectly with these newer lenses) but when it comes to using old m42 screwmount glass or old manual K-mount lenses the Pentax DSLRs meter all over the place.

I've found that using spot metering with Pentax DSLRs and old lenses produces the most consistent results, but I now use m42 and Pentax K-mount adapters on my Olympus cameras whenever I want to use an old lens for a particular look.
I think it is a question of which body you have.

To be honest, the *istD meters perfectly with old lenses, and has TTL flash so you can do everytinng with that body.

I agree the K10D has some difficulties metering, but they can be addressed with a different focusing screen, This is very important for people who use mostly old lenses, as they can make a change that resolves it totally for old lenses.

If you shoot both, the issue is do you make the change for old lenses, and then have a correction factor for each new lens, or do you live with new lenses working perfectly and correct for old lenses.

If I ever replace my K10D for every day shooting, I might just put an *istD screen in permantly, or a Katz eye and make it a manual only body
10-15-2008, 05:04 AM   #11
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QuoteOriginally posted by Lowell Goudge Quote
I think it is a question of which body you have.

To be honest, the *istD meters perfectly with old lenses, and has TTL flash so you can do everytinng with that body.

I agree the K10D has some difficulties metering, but they can be addressed with a different focusing screen, This is very important for people who use mostly old lenses, as they can make a change that resolves it totally for old lenses.

If you shoot both, the issue is do you make the change for old lenses, and then have a correction factor for each new lens, or do you live with new lenses working perfectly and correct for old lenses.

If I ever replace my K10D for every day shooting, I might just put an *istD screen in permantly, or a Katz eye and make it a manual only body
I have one K10D with a Katz Eye screen, one K10D with a cheap Chinese screen, on *ist DL with a cheap Chinese screen, and I've done extensive testing with the K20D and K100D Super (that I reviewed for a website before needing to send them back to Pentax).

I've never used the original *ist D with old lenses, so I suppose it's possible that the *ist D is more consistent with exposures when using manual lenses, but I've never seen very consistent results with the Pentax cameras I've used with manual lenses.

Again, the Pentax DSLRs I've used are more consistent with spot metering, but still not as consistent as when I mount those same lenses to an Olympus E-system body. Also, I've found that the Pentax DSLRs meter just fine when using newer lenses.
10-15-2008, 05:14 AM   #12
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QuoteOriginally posted by JJJPhoto Quote
I have one K10D with a Katz Eye screen, one K10D with a cheap Chinese screen, on *ist DL with a cheap Chinese screen, and I've done extensive testing with the K20D and K100D Super (that I reviewed for a website before needing to send them back to Pentax).

I've never used the original *ist D with old lenses, so I suppose it's possible that the *ist D is more consistent with exposures when using manual lenses, but I've never seen very consistent results with the Pentax cameras I've used with manual lenses.

Again, the Pentax DSLRs I've used are more consistent with spot metering, but still not as consistent as when I mount those same lenses to an Olympus E-system body. Also, I've found that the Pentax DSLRs meter just fine when using newer lenses.
Not to argue the point but have you posted the results from the extensive testing. I.e. measured and plotted greyscale as a function of apature in manual metering mode?

I would love to see the results
10-15-2008, 05:32 AM   #13
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Newbie question

QuoteOriginally posted by JJJPhoto Quote
Again, the Pentax DSLRs I've used are more consistent with spot metering, but still not as consistent as when I mount those same lenses to an Olympus E-system body.
Forgive the newbie question, folks. Do I understand from above that manual Pentax glass will mount directly on the Olympus E bodies? Do they use the same K mount as Pentax, or are we talking about an M42 to Oly-specific adapter ring?

Sorry if this was covered, didn't see it in the thread.

Regards,

germar
10-15-2008, 05:56 AM   #14
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QuoteOriginally posted by germar Quote
Forgive the newbie question, folks. Do I understand from above that manual Pentax glass will mount directly on the Olympus E bodies? Do they use the same K mount as Pentax, or are we talking about an M42 to Oly-specific adapter ring?

Sorry if this was covered, didn't see it in the thread.

Regards,

germar
There are M42 adaptors for many different types of SLRs. I believe canon also has one.
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