[Noisychip]

As most Pentaxians will know, M lenses can not be used with P-TTL flash. Flash alway fires at full power. Negative flash power compensation is also not possible, as is slow syncro and trailing curtain (IIRC).

I'd love to be able to use flash to a certain extent at least, because there are very nice and affordable M lenses especially for portraits.

How do you solve that problem? Sure, selling all M glass and buy all FA Limited would be one solution - pricey, though

Are there more creative approaches? Do any of you use grey filters on lens and/or in front of the flash? Any other cool ideas out there?

[arpaagent]

You won't be able to use your onboard flash with M series lenses on a digital body, unless you can somehow stop the lens down enough to get just the amount of light.

You can, however, use M lenses if you have an external flash that supports "Auto" mode, as most do. These flashes can be set to measure their own light output and cut off at the right time. You would just need to set your M lens to the correct aperture, and put your camera into manual mode, at a speed low enough (<1/180 for example on the K200D) that will sync with the flash. I have used older flashes (Pentax AF280T) like this and it works fine. The auto mode on these older flashes is pretty reliable and is quite usable. Not quite as worry-free as P-TTL, but works well under most situations, including bouncing off of ceilings and walls.

[Lowell Goudge]

I find myself contnually recommending that if people want a second / back up 6MP camera, they should get an *istD. Why? because it is fully TTL capable, both with hot shoe and internal flash.

NO other DSLR can do that.

If you are using a K10D yoru best option is to get an AF540 FGZ and use it in Auto mode (that's right, it has its own flash sensor just like the old days)

[stevebrot]

As hinted above, you will have to do it the old fashioned way. According to the K10D owner's manual, the guide number table is:

Code:

ISO                Guide Number
-------------------------------
100                    11
200                    15.6
400                    22
800                    31
1600                   44
-------------------------------

Aperture = guide number / shooting distance (meters)

So for ISO 200 at 3 meters the aperture is f/5.2 (may be safely rounded to f/5.6)

In practice, I make a quick guess, do a test shot, chimp the histogram, and adjust accordingly.

Steve

---

Last edited by stevebrot; 12-10-2008 at 03:22 PM.

[stevebrot]

You won't be able to use your onboard flash with M series lenses on a digital body, unless you can somehow stop the lens down enough to get just the amount of light.

You can, however, use M lenses if you have an external flash that supports "Auto" mode, as most do. These flashes can be set to measure their own light output and cut off at the right time. You would just need to set your M lens to the correct aperture, and put your camera into manual mode, at a speed low enough (<1/180 for example on the K200D) that will sync with the flash. I have used older flashes (Pentax AF280T) like this and it works fine. The auto mode on these older flashes is pretty reliable and is quite usable. Not quite as worry-free as P-TTL, but works well under most situations, including bouncing off of ceilings and walls.

A note of caution regarding external flash. Many older (and some newer) flashes have an overly high trigger voltage that may damage the circuitry of your camera. There have been a number of threads on this forum on the issue. There are also a few resources on the Web that have tables of known voltages.

Photo Strobe Trigger Voltages

There is some discussion about where the upper threshold of safety lies and I would be the last to make any suggestions, though there is some thought that under 7.8V is safe. (My old Vivitar flash measured in at 140V!)

Steve

P.S. You might also want to check out this poll https://www.pentaxforums.com/forums/pentax-camera-accessories/43200-flash-tri...nown-work.html

[CFWhitman]

I've used my AF540 in manual mode with a manual lens before. I mostly just calculated power by eye (1/1, 1/2, 1/4, 1/8, or 1/16). Take a few test shots to get the feel, and it doesn't seem too hard to get it right that way. You should be able to do this with older flashes too, but you should watch the trigger voltage as Steve mentioned.

[dlacouture]

Hello,

Well, in fact, you can trick the camera into thinking it has an A lens attached... Just short the A and Data electrical contacts on the mount, and Tadaaaaa! you've just enabled P-TTL and matrix metering (Focus point still stays centered, though).

It'll will even transform some PK-M lenses into PK-A (not all, you'll have to try!). To do this, just set the aperture ring on the smallest aperture available.

Only downside for m42 and pure PK-M (those not working as PK-A): you have to select the biggest aperture available on the body, or the pics will be overexposed.

[Mike Cash]

You won't be able to use your onboard flash with M series lenses on a digital body

I don't like to do it, but I have used onboard flash with M lenses and M42 lenses. You just have to know the GN and guesstimate your subject distance to get you in the ballpark of the correct aperture. Then review your histogram and adjust accordingly.

The option you outline of using external flashes with an auto feature is far preferable.

[richard64]

Well, in fact, you can trick the camera into thinking it has an A lens attached... Just short the A and Data electrical contacts on the mount, and Tadaaaaa!

Huh? With K and M lenses the mount on ther lens is metal, so all the contacts will be shorted. IIRC this is how the body detects that the lens is K or M rather than an A or later. Si IMO shorting the A and Data pins will do nothing because they are already shorted.

Perhaps you are thinking about this modification? Mark Roberts actually insulates part of the mount so that the camera can determine the maximum and minimum aperture.

you've just enabled P-TTL and matrix metering (Focus point still stays centered, though).

P-TTL means that the camera sends test flashes, and meters, then it adjusts the flash accordingly, do you see this with your modification?

When you say you get matrix metering, are you saying that you can set the camera to the matrix metering setting?

It'll will even transform some PK-M lenses into PK-A (not all, you'll have to try!). To do this, just set the aperture ring on the smallest aperture available. Only downside for m42 and pure PK-M (those not working as PK-A): you have to select the biggest aperture available on the body, or the pics will be overexposed.

If you have to use the smallest aperture then it means that the flash is using full power. This means that there is no metering from the body, so P-TTL is not working. If you could use any aperture (and you can change the flash power for the on-board flash using the menu) then it would mean that P-TTL is working.

Richard

[Lowell Goudge]

I've used my AF540 in manual mode with a manual lens before. I mostly just calculated power by eye (1/1, 1/2, 1/4, 1/8, or 1/16). Take a few test shots to get the feel, and it doesn't seem too hard to get it right that way. You should be able to do this with older flashes too, but you should watch the trigger voltage as Steve mentioned.

I'm surprised you didn't select Auto mode on the AF540, it has it's own sensor, and all you have to do on the flash is set the F-stop you set thelens to, the camera sends the ISO, and you are all set.

[Lowell Goudge]

lets just clarify a little, I've been there

Huh? With K and M lenses the mount on ther lens is metal, so all the contacts will be shorted. IIRC this is how the body detects that the lens is K or M rather than an A or later. Si IMO shorting the A and Data pins will do nothing because they are already shorted

no not all contacts touch the mount, the one that tells the camera that the lens is automatic apature (3rd from the locking pin) is recessed on the camera body, the pin must stick out from the lens

Perhaps you are thinking about this modification? Mark Roberts actually insulates part of the mount so that the camera can determine the maximum and minimum aperture.

this does not work, because the DSLRs disable matrix metering if the lens is out of auto apature mode I think mark roberts also states this only works on film bodies

P-TTL means that the camera sends test flashes, and meters, then it adjusts the flash accordingly, do you see this with your modification?

When you say you get matrix metering, are you saying that you can set the camera to the matrix metering setting?

if it is working, but you need the lens in auto mode to do this, meaning that you have to also short the third pin from the lens locking pin, and that causes all sorts of other problems. Specifically the camera now thinks it has an A lens, and tries to figure out the metering based on the other contacts, and gets it wrong. Also, when you short the A poin, the apature activation lever operates to the extent necessary to set the F stop on an A lens, which is not the same as a manual apature (Non A) lens

If you have to use the smallest aperture then it means that the flash is using full power. This means that there is no metering from the body, so P-TTL is not working. If you could use any aperture (and you can change the flash power for the on-board flash using the menu) then it would mean that P-TTL is working.

Richard

All of these work arounds in my opinion are a waste of time. I did an experiment where I actually converted a lens to A from K mount, by marking the apatures according to the Mark Roberts instructions AND adding the pin for Automatic apature. Did it work, sort of, but exposure is all over the map. Why? Because the apature activation lever on a non A lens controls the apature differently. Most Non A lenses have the apature change diameter linearly with motion of this lever, where A lenses have the area change linearly with this lever. As a result the converted Non A lens got the exposure wrong at every setting varrying from -1.5 stops at max apature to +2 stops at min apature. In other words, it was almost useless.

If you are serious about flash work with non A lenses, as I said earlier, you have at this point 2 options, get an *istD (or DS but on the DS the internal flash isnot TTL capable) or get an AF540 FGZ and use it in the Auto mode.

[roy]

the DS also works in TTL. that's why i'll keep mine..
this subject is my only peeve with pentax. all but the D&DS will not work in TTL. you can get around it but ti still PMO that they did this.

I find myself contnually recommending that if people want a second / back up 6MP camera, they should get an *istD. Why? because it is fully TTL capable, both with hot shoe and internal flash.

NO other DSLR can do that.

If you are using a K10D yoru best option is to get an AF540 FGZ and use it in Auto mode (that's right, it has its own flash sensor just like the old days)

[Mike Cash]

If you are serious about flash work with non A lenses, as I said earlier, you have at this point 2 options, get an *istD (or DS but on the DS the internal flash isnot TTL capable) or get an AF540 FGZ and use it in the Auto mode.

Or any of several other flashes that have an auto mode.

[Lowell Goudge]

the DS also works in TTL. that's why i'll keep mine..
this subject is my only peeve with pentax. all but the D&DS will not work in TTL. you can get around it but ti still PMO that they did this.

Roy

does the internal flash on teh DS work also in TTL mode, SOmeone posted earlier it did not.

I know the *istD does.

As per your pet peeve, my wish list for the next high end, i.e. K30D is that it returns with the TTL sensor reading off the sensor plane. Why, not because I like to use old glass, but because for wildlife, the preflash disturbes the subject, and sometimes the pose is lost, and the lag that preflash adds results in less perfext shots. For wildlife, TTL is the only way to go.

[bdery]

The best advice is, indeed, to get a flash that has an auto Thyristor mode, and set the exposure parameters accordingly. No problems then.