[viper56]

I have a Metz AF24 pttl flash. It does not have a manual mode at all. I was trying to get it to work with an older M lens. Is this possible and if so how do I do this?

[Lowell Goudge]

P-TTL flash simply does not work with older lenses because they lack the aperture coding.

Just so you understand, P-TTL flash is a predictive flash, as opposed to the older TTL flash which is reactive.

TTL flash terminated the flash when the combined light from exposure plus flash was deemed correct, but had problems because the exposure can continue on for some time after the flash ends, therefore, the longer the shutter speed, the larger the exposure error.

P-TTL flash meters the natural scene, with open aperture metering, and also measures the impact of the preflash, on the overall scene, and can therefore predict, knowing the open aperture value, AND the selected shooting aperture, and the ambient light, the correct flash duration for the scene, that's the theory any way.

SO unless your lens has aperture coding and an A setting, it simply lacks the data it needs, so it fires at full flash intensity.

this means you have only 2 levers of control for exposure, ISO and Aperture. and you need to do the manual flash calculations for the full guide number.

There are some reported hacks, including using bits of tinfoil to trick the camera into thinking it has an A lens connected, but these all require corrections to get things right.

[RioRico]

What Lowell said. Using old TTL flash with our pTTL dSLRs and lenses lacking A contacts is a royal pain in the butt real challenge. The most straightforward approach, besides the tinfoil trick, is just to calculate, with much trial+error. Keep tweaking aperture+shutter+ISO+distance+filters+diffusers, and testing exposures, and chimping and re-tweaking, until you get something acceptable. Or stick with A-type and AF lenses when using TTL flash. Good luck!

[Anvh]

A flash with Auto-mode will work and you can get them from a couple of dollars second hand.

[grhazelton]

A flash with Auto-mode will work and you can get them from a couple of dollars second hand.

And of course you can look at the LCD to evaluate the result. This is how I use my AF400T "flame thrower."

[Anvh]

But not everyone is confident enough to use the flash in manual mode but it surely is an option.

[JimJohnson]

P-TTL flash DOES work with non-A lenses. Only a quick, minor and completely reversible modification to the camera is needed. There are several threads on fooling your camera into thinking all lenses have the 'A' setting.

[Anvh]

Does it then still meter correctly?

[Lowell Goudge]

P-TTL flash DOES work with non-A lenses. Only a quick, minor and completely reversible modification to the camera is needed. There are several threads on fooling your camera into thinking all lenses have the 'A' setting.

You will note I mentioned there is a hack

Does it then still meter correctly?

no, it needs adjustments because the open aperture metering is done with the aperture configuration of all pins shorted, I forget what that is without looking it up. Your lens will not be at that native aperture, therefore, it is applying open aperture readings to the wrong aperture. Then there is the potential interference of the aperture activating lever, which will move only as far as the aperture setting suggests it should move. This may or may not limit the aperture different to what you mechanically set.

Also note it does not work for M42 lenses, for the same reasons. It gives a measure of control, but that is all.

If you really want flash with legacy lenses, the two reliable ways are to use a flash with an auto sensor built in, just like the old data , or get an *istD which supports both TTL and PTTL

[dlacouture]

No, it does work with m42 and PK-M lenses... What is needed is:
- short the A pin,
- on the camera, select the widest aperture available,
- use a preset lens (either a m42 lens, or a modified PK-M lens) set to the wanted aperture (the viewfinder will darken).

This will enable full P-TTL support for legacy lenses.

Edit: a modified PK-M lens is one where the aperture lever does not engage the camera's coupler anymore, either by cutting or bending it (savage way), or by drilling a second locking hole into the lens so it will lock halfway turned into the mount.

[JimJohnson]

You will note I mentioned there is a hack ... no, it needs adjustments because the open aperture metering is done with the aperture configuration of all pins shorted,

Yes, but the hack is quick and non-destructive. In addition to shorting the "A" pin on the body, you need to communicate the lens' minimum and maximum apertures by putting insulators (Magic Tape) on the lens mount to emulate a KA lens. You can permanently insulate contacts too, but I have no idea what that might do to the lens' value - probably drop it for a collector, but increase it for a working photographer.

I have a couple posts in this thread on using the same technique to fit inexpensive extension tubes and retain full automation:
https://www.pentaxforums.com/forums/pentax-camera-field-accessories/113756-pk...ion-tubes.html
I also showed yesterday in another thread that the same technique allowed the photographer to mount a DA lens (no aperture ring) on less expensive extension tubes and still retain automation.

Here is my example of mounting a manual lens and obtaining P-TTL flash automation:
https://www.pentaxforums.com/forums/pentax-k-r/187981-onboard-flash-manual-le...ml#post1974314

I don't disagree at all with the thought that using an auto-thyristor flash is going to be a much easier solution in most cases. Rather, I am trying to say never say never. And fooling your camera into thinking you have an "A" lens is sometimes the only way you can use some fine older glass with the other equipment you have at hand.

[Lowell Goudge]

Yes, but the hack is quick and non-destructive. In addition to shorting the "A" pin on the body, you need to communicate the lens' minimum and maximum apertures by putting insulators (Magic Tape) on the lens mount to emulate a KA lens. You can permanently insulate contacts too, but I have no idea what that might do to the lens' value - probably drop it for a collector, but increase it for a working photographer.

I have a couple posts in this thread on using the same technique to fit inexpensive extension tubes and retain full automation:
https://www.pentaxforums.com/forums/pentax-camera-field-accessories/113756-pk...ion-tubes.html
I also showed yesterday in another thread that the same technique allowed the photographer to mount a DA lens (no aperture ring) on less expensive extension tubes and still retain automation.

Here is my example of mounting a manual lens and obtaining P-TTL flash automation:
https://www.pentaxforums.com/forums/pentax-k-r/187981-onboard-flash-manual-le...ml#post1974314

I don't disagree at all with the thought that using an auto-thyristor flash is going to be a much easier solution in most cases. Rather, I am trying to say never say never. And fooling your camera into thinking you have an "A" lens is sometimes the only way you can use some fine older glass with the other equipment you have at hand.

Jim

a long time ago I converted a ricoh 50mm F2 to PKA by adding a spring loaded pin in the A pin location and by spot drilling the aperture coding into the lens mount. the results, while it did somewhat function, had serious errors due to the interference i.e. relitive movement of the aperture control lever and the lens action when stopping down. it seems that the aperture movement of K mount lenses cannot be successfully implemented unless the aperture lever is allowed to be fully released, which means that the only correct apertures are wide open and fully stopped down, all others have errors regardless of how you set them, i.e. in body, with lens at F22 or what ever, or combined in body and aperture ring., Exposure errors ranged from -1 to +2 stops, and while I agree this is infinitely better than full flash power every time, it by no means results in reliable exposure control. As i said, it is a hack.

[JimJohnson]

a long time ago I converted a ricoh 50mm F2 to PKA ... it seems that the aperture movement of K mount lenses cannot be successfully implemented unless the aperture lever is allowed to be fully released, which means that the only correct apertures are wide open and fully stopped down, all others have errors regardless of how you set them

Good information. You went further than I would to convert a lens. I am not sure with your description, could you confirm a couple points? Did you retry this lens on a current dSLR? And did you set the same aperture value both on the lens' aperture ring and within the camera body?

When I look at how the aperature works mechanically when off-camera, the aperture is sprung to completely close the aperture. The aperture ring moves not only the blades to the desired position but also the aperture lever to a coresponding position, the ring prevents the lens from closing further than a specific position. On an A lens, there is no difference in aperture between the smallest designed aperture and the A position. The only additional change is the A pin is extended from the lens.

When the lens is mounted to the camera, a cooresponding lever in the body pushes against the spring in the lens to fully open the aperture. On a non-A camera body during exposure, the body side of the lever would move to fully release the lens' lever - which would then stop at the pre-set point based on the aperture ring. However, on a A type camera body, when the camera believes an A type lens is attached, the body side of the lever moves only far enough to allow the lens to stop down to the aperture specified by the camera's electronics. The correct aperture is a percentage of the available lever movement, and why it is critical the body knows both the minimum and maximum available apertures.

In theory, if I have pre-shorted the A pin on the body and set the same aperture on both the lens and the camera, during exposure, the body side of the lever would stop movement at exactly the same distance as my lens' lever would allow. There are only two possible variations:

If the body side of the lever moves farther than the aperture set on the lens, the aperture would still be the value set on the lens because the lens would mechanically prevent the lens from stopping down further.
If the body side of the lever stops short of the aperture set on the lens, the aperture opening would also stop short of the value set on the aperture ring. The photograph would be overexposed according to the meter.

Unless the camera body has misinterpreted the lens' minimum and maximum aperture (and therefore how far the aperture lever would move for a given intermediate aperture), or the camera's meter misreads the exposure at full aperture, I cannot see how you could achieve under exposure. And overexposure whould be limited by however far short the body side lever travelled.

All of this assumes that a lens' lever movement correspondes to Pentax's calculations as to what percentage of movement equates to a specific f/stop. I think it is pretty safe to assume all lenses specificed as Pentax compatible do just this. I don't know if an alternate K-mount lens would do this. And I mean that literally, I don't know - I am not making any claim that alternate K-mount compatible lens do or don't.

What I can say is with my experimentation - and all my limited collection of lenses are all specified Pentax compatible - my hacking has produced exposure on my K-r body as accurate as what I see with my Pentax DA lens.

Given the equipment specified by the OP and how easy it is to make these easy, fully reversible modifications, it would be worth it to me to give it a try and see what happens.

[Lowell Goudge]

Good information. You went further than I would to convert a lens. I am not sure with your description, could you confirm a couple points? Did you retry this lens on a current dSLR? And did you set the same aperture value both on the lens' aperture ring and within the camera body?

i tried thiis with a K10D so that i couold use the internal flash with legacy lenses just like my *istD which supports both TTL and P-TTL, I tried both setting aperture on the lens to F22 and let the camera control it fully, and also matching settings. both gave similar results, but open aperture the metering was spot on.

When I look at how the aperature works mechanically when off-camera, the aperture is sprung to completely close the aperture. The aperture ring moves not only the blades to the desired position but also the aperture lever to a coresponding position, the ring prevents the lens from closing further than a specific position. On an A lens, there is no difference in aperture between the smallest designed aperture and the A position. The only additional change is the A pin is extended from the lens.

true, but the rate of change of diameter is different, on a K lens the movement is proportional to diameter, on an A lens proportional to area, or diameter squarred

When the lens is mounted to the camera, a cooresponding lever in the body pushes against the spring in the lens to fully open the aperture.

the lever moves to the theoretical distance of the number of stops set on the body

On a non-A camera body during exposure, the body side of the lever would move to fully release the lens' lever - which would then stop at the pre-set point based on the aperture ring.

yes

However, on a A type camera body, when the camera believes an A type lens is attached, the body side of the lever moves only far enough to allow the lens to stop down to the aperture specified by the camera's electronics. The correct aperture is a percentage of the available lever movement, and why it is critical the body knows both the minimum and maximum available apertures.

yes again, but the movement in terms of number of stops is linear on an A body and total range divided by number of stops determines the amount of lever movement,

In theory, if I have pre-shorted the A pin on the body and set the same aperture on both the lens and the camera, during exposure, the body side of the lever would stop movement at exactly the same distance as my lens' lever would allow.

no, this is assuming the lever movement is the same on K and A lenses, IT IS NOT that is the problem

There are only two possible variations:

If the body side of the lever moves farther than the aperture set on the lens, the aperture would still be the value set on the lens because the lens would mechanically prevent the lens from stopping down further.
If the body side of the lever stops short of the aperture set on the lens, the aperture opening would also stop short of the value set on the aperture ring. The photograph would be overexposed according to the meter.

see above the action is not the same for K and A lenses

Unless the camera body has misinterpreted the lens' minimum and maximum aperture (and therefore how far the aperture lever would move for a given intermediate aperture), or the camera's meter misreads the exposure at full aperture, I cannot see how you could achieve under exposure. And overexposure whould be limited by however far short the body side lever travelled.

All of this assumes that a lens' lever movement correspondes to Pentax's calculations as to what percentage of movement equates to a specific f/stop. I think it is pretty safe to assume all lenses specificed as Pentax compatible do just this. I don't know if an alternate K-mount lens would do this. And I mean that literally, I don't know - I am not making any claim that alternate K-mount compatible lens do or don't.

What I can say is with my experimentation - and all my limited collection of lenses are all specified Pentax compatible - my hacking has produced exposure on my K-r body as accurate as what I see with my Pentax DA lens.

Given the equipment specified by the OP and how easy it is to make these easy, fully reversible modifications, it would be worth it to me to give it a try and see what happens.

the whole argument makes sense except that as I point out above, the movement of the aperture for a K lens is not the same as that for an A lens, and as a result, the whole thing breaks down badly

[JimJohnson]

the whole argument makes sense except that as I point out above, the movement of the aperture for a K lens is not the same as that for an A lens, and as a result, the whole thing breaks down badly

I love this discussion! Note to viper56, I do still suggest you give my suggested modification a try. There is no risk to either camera or lens.

Okay, Lowell. I don't know enough to contest your description of relative lever movement between A-series and non-A-series K-mount lens and its impact on effective aperture, so I'm not going to bother. We agree that full open aperture metering would be the same for either lens series.

I am however having trouble seeing how a photograph could be under exposed when the lens' minimum sized aperture is controlled by the lens via its aperture ring. If the body's lever moves either just far enough or too far, the lens' aperture ring will stop the lens from closing further than the lens' calibrated f/stop. And I have to assume that calibration is far more accurate than the camera body's estimate of relative lever position.

Over exposure would be a whole different critter. If the body's lever stops short, the lens won't close all the way to the value on the lens' aperture ring and there isn't anything the lens' own aperture setting can do about it. And over exposure wouldn't be like the lens was stuck wide open. It would be whatever the difference might be in effective aperture for the two lens series - a quarter stop? half-stop? full stop? more? Regardless, unless critical highlights are blown, the image should be salvageable in post processing.

If my thoughts are wrong, I'm hoping you can help me see my mistake. Seriously. Because if I'm wrong it will impact one of my upcoming projects.