Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-04-2008, 10:56 PM   #1
Veteran Member
morfic's Avatar

Join Date: Feb 2008
Location: San Antonio, TX
Photos: Gallery
Posts: 428
P-TTL W/ manual lenses

Can't find the thread where it's mentioned with manual lenses, you are stuck with full power on built-in flash, and that's true.
Now i wonder, does this apply to all P-TTL flashes? external and internal?
After seeing how Pentax does a nicer job on supporting old lenses with regard to focus confirmation and stopping them down and metering, it seems odd they missed flash exposures.
As a canon convert i love all those things, i am just surprised we can't get p-ttl with manual lenses, even Canon got that one right

So, P-ttl with manual lenses and external flash, yes or no?

Thanks,

Daniel

05-05-2008, 01:25 AM   #2
Veteran Member




Join Date: Dec 2007
Posts: 923
P-TTL will work with almost any lens with "A" setting on the aperture ring.
The P-TTL compatibility is related to the Auto-Exposure capability of the lens rather than autofocus.

Its in the K10D/ K100D manual, together with the few exceptions to this.

For pre-A lenses, P-TTL will fire at full power. That's because the camera can't get the signal of what is the exposure setting. I thought it was the same with Canon ?

In such cases its probably best to use "Auto" Flash on an AF360/AF540 rather than P-TTL.
05-05-2008, 01:27 AM   #3
Veteran Member
kuuan's Avatar

Join Date: Dec 2007
Location: Austria
Photos: Gallery
Posts: 401
QuoteOriginally posted by morfic Quote
......

So, P-ttl with manual lenses and external flash, yes or no?

Thanks,

Daniel
there seems to be a work around, see:

jr-worldwi.de: Photography: Technic

( just found this interesting resource, and would be very happy if I better understood how much of an advantage TTL flash support really is..)

cheers,
Andreas

Last edited by kuuan; 05-05-2008 at 02:07 AM.
05-05-2008, 05:14 AM   #4
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,314
QuoteOriginally posted by kuuan Quote
there seems to be a work around, see:

jr-worldwi.de: Photography: Technic

( just found this interesting resource, and would be very happy if I better understood how much of an advantage TTL flash support really is..)

cheers,
Andreas
Note the "work around" will function but metering of the flash will be wrong, because it won't know the lens apature range correctly, and because the apature movement is different on K lenses (apature lever movement proportional to diameter not area) therefore having a functioning but worng flash is not much value.

05-05-2008, 07:40 AM   #5
Veteran Member
morfic's Avatar

Join Date: Feb 2008
Location: San Antonio, TX
Photos: Gallery
Posts: 428
Original Poster
QuoteOriginally posted by kittykat46 Quote
I thought it was the same with Canon ?
IT may be the only ting they got right, but using any old manually stopped down lens creates a properly exposed shot. The camera really wouldn't concern itself with the aperture, it sends a preflash, and basedon that measurement then sets flash power required for a full exposure, the camera also has no idea about the aperture used, but the preflash gives it enough feedback to get it right.

That's why i was surprised Pentax chose to just shoot full power if it doesn't get feedback from the lens.
Wish they would add that to the firmware, as P-TTL using a preflash would be just as capable to meter (w/o knowing an aperture) using that as other brands can/do. I'd take a custom function on this, if it's left out since it's considered to break legacy behavior?

Daniel

(Since i keep reading how bad the manual is on almost every thread here, i barely cracked it open (I will, don't worry.))

Last edited by morfic; 05-05-2008 at 07:57 AM.
05-05-2008, 07:50 AM   #6
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,314
QuoteOriginally posted by morfic Quote
IT may be the only ting they got right, but using any old manually stopped down lens creates a properly exposed shot. The camera really wouldn't concern itself with the aperture, it sends a preflash, and basedon that measurement then sets flash power required for a full exposure, the camera also has no idea about the aperture used, but the preflash gives it enough feedback to get it right.

That's why i was surprised Pentax chose to just shoot full power if it doesn't get feedback from the lens.

Since i keep reading how bad the manual is on almost every thread here, i barely cracked it open
I have offered pentax 2 solutions to this issue, and they have not implemented either.

solution 1,

Press the green button and let the camera determine the ration of light wide open to stopped down, then set P-TTL accordingly

Solution 2

allow useer inout of lens data, min and max apature and then control the apature and flash set by the camera.
05-05-2008, 04:09 PM   #7
Veteran Member
morfic's Avatar

Join Date: Feb 2008
Location: San Antonio, TX
Photos: Gallery
Posts: 428
Original Poster
Lowell: What they should do is, in either green button mode, AE-L press or every time shutter is fully pressed (custom function?) is meter the scene with the preflash, with the lens stopped down, be it a M42 lens already stopped down, or a K mount lens after the lever moved out of the way to allow lens to close.
It does not need to know the aperture range of the lens, nor does it need to know which aperture the lens is set to, sounds overly complicated to tell cam such info to be honest.
Using the preflash in either green button, AE-L or full shutter press would allow the cam to determine the brightness of the subject, and how much power is required to full light the subject.
This should easily work in M (and even Av) if the preflash would be used when a manual lens is attached. So rather than cheating the cam into thinking a certain aperture is used on a newer mount, have it use a much simpler algorithm for a K mount.
This would easily get us within a FEC range, which i wouldn't mind, heck, slap a 580EX on a 5D and tell me you will not end up with -1 to -2 FEC when using e-ttl II on a fully microchipped lens
The FEC should be pretty consistent for a given lens and aperture.
(I admit, i might be describing your solution 1, i just don't get the need for a wide open to stopped down ratio, especially since M42 lenses would never see a pre-flash wide open)

So for K-Mount (or M42 in K-Mount adapter) it woud go like this:

Press shutter.
Cam stops down K mount lens (M42 are already manually stopped down by user)
Cam sends out pre-flash.
Cam receives data (light) back.
Cam calculates the flash power required to light subject.
Cam opens shutter curtain all the way.
Flash fires close to perfect power.
Shutter curtain closes.

We evaluate and adjust FEC.
We keep happily shooting the event with our old K-mount lenses for the rest of the day.

And i am convinced Pentax could turn the K20D into an even better product when it comes to legacy support, with a simple firmware update that incorporates this.
And for those that actually like the whole full power flash thing it could be default, with "our way" being a custom function choice.
05-05-2008, 06:09 PM   #8
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,314
QuoteOriginally posted by morfic Quote
Lowell: What they should do is, in either green button mode, AE-L press or every time shutter is fully pressed (custom function?) is meter the scene with the preflash, with the lens stopped down, be it a M42 lens already stopped down, or a K mount lens after the lever moved out of the way to allow lens to close.
It does not need to know the aperture range of the lens, nor does it need to know which aperture the lens is set to, sounds overly complicated to tell cam such info to be honest.
Using the preflash in either green button, AE-L or full shutter press would allow the cam to determine the brightness of the subject, and how much power is required to full light the subject.
This should easily work in M (and even Av) if the preflash would be used when a manual lens is attached. So rather than cheating the cam into thinking a certain aperture is used on a newer mount, have it use a much simpler algorithm for a K mount.
This would easily get us within a FEC range, which i wouldn't mind, heck, slap a 580EX on a 5D and tell me you will not end up with -1 to -2 FEC when using e-ttl II on a fully microchipped lens
The FEC should be pretty consistent for a given lens and aperture.
(I admit, i might be describing your solution 1, i just don't get the need for a wide open to stopped down ratio, especially since M42 lenses would never see a pre-flash wide open)

So for K-Mount (or M42 in K-Mount adapter) it woud go like this:

Press shutter.
Cam stops down K mount lens (M42 are already manually stopped down by user)
Cam sends out pre-flash.
Cam receives data (light) back.
Cam calculates the flash power required to light subject.
Cam opens shutter curtain all the way.
Flash fires close to perfect power.
Shutter curtain closes.

We evaluate and adjust FEC.
We keep happily shooting the event with our old K-mount lenses for the rest of the day.

And i am convinced Pentax could turn the K20D into an even better product when it comes to legacy support, with a simple firmware update that incorporates this.
And for those that actually like the whole full power flash thing it could be default, with "our way" being a custom function choice.

This is exactrly what I told them. Calculate with the camera meter, specifically the change in light when stopped down from wide open.

All that matters is the number of f stops. BUT and this is a big one. The K10D metering is screwed up and unreliable. It does not meter correctly with Manual apature lenses, at F1.4 it is 1 to 1.5 stops under exposure, shifting to correct by F4 to +2 stops over exposed by F11. This is due to the reflective properties of the focusing screen. SO there is a problem, either replace all focusing screens and re-calibrate exposure, or allow to enter the apature in software.

Note this is how it meters correctly with AE lenses. Take them out of AE mode and they meter just as badly as manual apature lenses

05-05-2008, 06:22 PM   #9
Veteran Member
morfic's Avatar

Join Date: Feb 2008
Location: San Antonio, TX
Photos: Gallery
Posts: 428
Original Poster
the under, correct over exposure is just a shifted version of Canon's correct wide open to increasing amounts of overexposure as you stop down.
Note that Canon's mismetering does not interfere much with e-ttl (II).
Perhaps it's easier to deal with since i tend to change apertures much less when using flash. So the amounts of EC and FEC won't change much (FEC on my 30D was always at -1, rarely i had to move it, and if i did, mostly to -2, manual or automatic alike)

Point is, Pentax could get us a mode very easily that works even on permanently stopped down M42 lenses due to P-TTL already using a preflash, there is no reason to just go "Hm, a manual lens, 1/1 power it is!"

If P-TTL relies on an aperture, SR asks for a focal length, they could ask for a "Flash Aperture" just as well, i can't let go of the whole idea of "ignore the aperture and use the preflash on manual lenses", since i saw it working on the 30D, that cam has no clue about the aperture of any adapted lens attached, and if you use a focus confirm chip on your adapter (on 30D) you even fake the cam to think it's a f/2.0 - 2.0 lens it has attached, yet flash exposure is still "correct" (within the usual/typical e-ttl II margin of error)

Last edited by morfic; 05-05-2008 at 09:54 PM.
05-06-2008, 03:59 AM   #10
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,314
QuoteOriginally posted by morfic Quote
the under, correct over exposure is just a shifted version of Canon's correct wide open to increasing amounts of overexposure as you stop down.
Note that Canon's mismetering does not interfere much with e-ttl (II).
Perhaps it's easier to deal with since i tend to change apertures much less when using flash. So the amounts of EC and FEC won't change much (FEC on my 30D was always at -1, rarely i had to move it, and if i did, mostly to -2, manual or automatic alike)

Point is, Pentax could get us a mode very easily that works even on permanently stopped down M42 lenses due to P-TTL already using a preflash, there is no reason to just go "Hm, a manual lens, 1/1 power it is!"

If P-TTL relies on an aperture, SR asks for a focal length, they could ask for a "Flash Aperture" just as well, i can't let go of the whole idea of "ignore the aperture and use the preflash on manual lenses", since i saw it working on the 30D, that cam has no clue about the aperture of any adapted lens attached, and if you use a focus confirm chip on your adapter (on 30D) you even fake the cam to think it's a f/2.0 - 2.0 lens it has attached, yet flash exposure is still "correct" (within the usual/typical e-ttl II margin of error)

All I can suggest is you write pentax directly, not bitch about it in the forum because we can't change this.

I have written pentax about this issue, and a list of others which are all software correctable flaws in the K10D and have now reached a point where they don't even respond to my requests. The more people who write them, and advise them of a functional problem, the better the chance they will change.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, canon, dslr, flash, lenses, p-ttl, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
P-TTL w/ manual lenses? gsrokmix Troubleshooting and Beginner Help 25 04-18-2012 12:18 PM
P-TTL flash - Camera in Manual mode - ISO shouldn't change exposure right? Josť Ramos Flashes, Lighting, and Studio 5 05-29-2010 10:00 PM
goodbye P-TTL, hello manual flash WMBP Flashes, Lighting, and Studio 14 08-28-2009 10:39 PM
Non-ttl / manual flash confusion Sasquatch Pentax Film SLR Discussion 7 02-04-2009 03:22 PM



All times are GMT -7. The time now is 10:21 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top