[West Penn]

The overall tone of the subject being photographed dictates exposure when using P-TTL. White objects will be underexposed, black objects will be overexposed. It's the nature of P-TTL -- it's simply reacting to reflected light. Since the paneled wall is a light tone, it was underexposed and would require exposure compensation to achieve proper exposure.

[stevebrot]

Doing a little reading last night on how P-TTL actually works. Apparently there's more user input required then the marketing hype leads you to believe. Haven't had the opportunity to test it out, but it seems using both camera EC and flash EC is necessary. I also suspect that it is somewhat dependent on what your camera exposure metering mode is set to. Normally I leave it on Spot, but I was recently at an event where I switched to Matrix, and forgot to change it back.

The same writeup I was reading also mentioned using camera manual and setting the flash to P-TTL. I was unaware that was possible. I had erroneously assumed that you had to use both on Manual. I forsee more experiments ahead.

It is not well-appreciated, but P-TTL flashes take their orders from the camera. In short, they never over/under-expose unless told to do so or left with no other alternative (error conditions).

At core is the simple fact that the camera is serving as a TTL version of a flash meter with all the normal potential shortcomings of TTL light metering. Based on the meter reading, the flash is instructed on how much intensity to provide. If presented with a blank white wall, the meter will center the histogram with a "proper", though somewhat gray-looking exposure. If presented with a gray-toned gallery wall, the results will be equally proper, but more true.

Yes, camera metering mode is important. For best results, use matrix metering or center-weighted. Spot metering, even for non-flash photos, is a specialized tool and a sure guarantee for poor exposures unless used with a specific purpose in mind.* I tried, but could not think of a use case for spot metering with flash photography.

In-camera flash EC on my setup (K-3 and Sigma EF 610 DG Super) is additive to on-flash P-TTL EC. The genera exposure comp applies to ambient light, but will have an effect overall when flash is part of the mix.

Sometimes old-school manual flash using distance and guide number can be useful in diagnosing. I took the conditions from your second (manual flash) example and back calculated what the guide number exposure should be. According the tables in the user guide, the flash exposure in your example is about two stops over, based solely on ISO and distance.


Steve

* Exposure problems are a common help topic on this site and one of the most frequent causes for unexpected over/under exposure is use of spot metering for general photography. Unless one really wants Aunty Ida's face to be rather middle grayish, it is best to avoid spot unless wanting to place exposure (think Zone System) when using M mode.

[C_Jones]

Doing a little reading last night on how P-TTL actually works. Apparently there's more user input required then the marketing hype leads you to believe. Haven't had the opportunity to test it out, but it seems using both camera EC and flash EC is necessary. I also suspect that it is somewhat dependent on what your camera exposure metering mode is set to. Normally I leave it on Spot, but I was recently at an event where I switched to Matrix, and forgot to change it back.

The same writeup I was reading also mentioned using camera manual and setting the flash to P-TTL. I was unaware that was possible. I had erroneously assumed that you had to use both on Manual. I forsee more experiments ahead.

The way that I explained is the way I actually use my camera and flash, with camera in manual mode and flash in P-TTL mode. I am able to choose the shutter speed, aperture and ISO to the settings I see best fit when I use manual. If I switch to a camera auto mode, I do not have full control of what I may need for an image outcome, so I avoid using camera auto modes with my flash. For example, I could set my ISO to 200 or 400 depending on light needs, shutter speed to something reasonable according to how fast my subjects are moving (125 for stills or slow movement, something higher for faster movement), and the aperture to something that would provide detail in what I want to see in the image (depth of field to cover the subject). I usually use spot metering and spot AF area (center point). If the subject is partially covered in light and part not, then I try to focus on an area that is a sort of median if I can and crop what I want of the scene later. Something to note is that while using flash, you can have your subjects turned so that they are not facing direct sunlight, then you an use the flash P-TTL more effectively being that the subjects are lit evenly for the most part when not facing the sun.

When I use the camera in manual and the flash in P-TTL, I also have my camera exposure mode to "Flash" or "Daylight" which will usually give me relatively correct lighting. As you said, your metering method does work with what the camera and flash are going to figure as the lighting existent in the scene, and if you want to adjust that you may want to adjust the flash or camera exposure as you see fit. If it was me I would most likely adjust the flash exposure setting, but both are available.

Good luck with your experiments. The hands on use will always tell you what suits your style best and what you may like to avoid.

[Smoke665]

The way that I explained is the way I actually use my camera and flash, with camera in manual mode and flash in P-TTL mode. I am able to choose the shutter speed, aperture and ISO to the settings I see best fit when I use manual. If I switch to a camera auto mode, I do not have full control of what I may need for an image outcome, so I avoid using camera auto modes with my flash. For example, I could set my ISO to 200 or 400 depending on light needs, shutter speed to something reasonable according to how fast my subjects are moving (125 for stills or slow movement, something higher for faster movement), and the aperture to something that would provide detail in what I want to see in the image (depth of field to cover the subject). I usually use spot metering and spot AF area (center point). If the subject is partially covered in light and part not, then I try to focus on an area that is a sort of median if I can and crop what I want of the scene later. Something to note is that while using flash, you can have your subjects turned so that they are not facing direct sunlight, then you an use the flash P-TTL more effectively being that the subjects are lit evenly for the most part when not facing the sun.

When I use the camera in manual and the flash in P-TTL, I also have my camera exposure mode to "Flash" or "Daylight" which will usually give me relatively correct lighting. As you said, your metering method does work with what the camera and flash are going to figure as the lighting existent in the scene, and if you want to adjust that you may want to adjust the flash or camera exposure as you see fit. If it was me I would most likely adjust the flash exposure setting, but both are available.

Good luck with your experiments. The hands on use will always tell you what suits your style best and what you may like to avoid.

Well I should've known there's no shortcuts. Went to manual on the camera, flash on P-TTL and camera EC to get consistent repeatable results. Then added a modifier to the flash raising the EC on the flash to compensate. Think I have a workable solution now.

---------- Post added 05-05-21 at 04:07 PM ----------

It is not well-appreciated, but P-TTL flashes take their orders from the camera. In short, they never over/under-expose unless told to do so or left with no other alternative (error conditions).

At core is the simple fact that the camera is serving as a TTL version of a flash meter with all the normal potential shortcomings of TTL light metering. Based on the meter reading, the flash is instructed on how much intensity to provide. If presented with a blank white wall, the meter will center the histogram with a "proper", though somewhat gray-looking exposure. If presented with a gray-toned gallery wall, the results will be equally proper, but more true.

Yes, camera metering mode is important. For best results, use matrix metering or center-weighted. Spot metering, even for non-flash photos, is a specialized tool and a sure guarantee for poor exposures unless used with a specific purpose in mind.* I tried, but could not think of a use case for spot metering with flash photography.

In-camera flash EC on my setup (K-3 and Sigma EF 610 DG Super) is additive to on-flash P-TTL EC. The genera exposure comp applies to ambient light, but will have an effect overall when flash is part of the mix.

Sometimes old-school manual flash using distance and guide number can be useful in diagnosing. I took the conditions from your second (manual flash) example and back calculated what the guide number exposure should be. According the tables in the user guide, the flash exposure in your example is about two stops over, based solely on ISO and distance.


Steve

* Exposure problems are a common help topic on this site and one of the most frequent causes for unexpected over/under exposure is use of spot metering for general photography. Unless one really wants Aunty Ida's face to be rather middle grayish, it is best to avoid spot unless wanting to place exposure (think Zone System) when using M mode.

I think based on marketing hype, I mistakenly believed the communication was a two-way street, when in reality it's not. Once I understood how it worked it didn't take long to dial it in.

Thanks for the help everyone.

[C_Jones]

Well I should've known there's no shortcuts. Went to manual on the camera, flash on P-TTL and camera EC to get consistent repeatable results. Then added a modifier to the flash raising the EC on the flash to compensate. Think I have a workable solution now.

---------- Post added 05-05-21 at 04:07 PM ----------



I think based on marketing hype, I mistakenly believed the communication was a two-way street, when in reality it's not. Once I understood how it worked it didn't take long to dial it in.

Thanks for the help everyone.

Sounds like you are getting some well controlled results. Congratulations and happy shooting!

[stevebrot]

I think based on marketing hype, I mistakenly believed the communication was a two-way street, when in reality it's not.

There is some exchange, but the two are "loosely" bound for the case of single flash. I don't know for certain, but it appears the flash provides a guide number range (or equivalent) along with with the usual flash ready. Of course, thing like HSS and second curtain sync require a few more bits from the flash.

Multi-flash, either wired or optical is another matter entirely and I have no idea how the logic is split up, particularly for wired with 5P cabling.


Steve

[Smoke665]

There is some exchange, but the two are "loosely" bound for the case of single flash. I don't know for certain, but it appears the flash provides a guide number range (or equivalent) along with with the usual flash ready. Of course, thing like HSS and second curtain sync require a few more bits from the flash.

Multi-flash, either wired or optical is another matter entirely and I have no idea how the logic is split up, particularly for wired with 5P cabling.


Steve

I have a few odd speed lights for location shots where I don't want to lug studio equipment around. Primarily I used Youngnu with simple wireless triggers and a light meter to set them up, worked well for years. The whole purpose of going with the Pentax flash was to simplify and speed up the process, unfortunately it's not been anything close.

The first problem I encountered was moving off camera. A simple cable should have been the solution, but two different inexpensive Vello cables (despite working on the FGZ) refused to work on the FGZII. Calls to customer service at both Vello and Pentax had everyone scratching their heads, with the final solution...use the 5P cable. To this day having thoroughly inspected both cables I am clueless as to why one works and the cheaper one doesnt.

Supposedly another advantage of the 360FGZII is the ability to do ratios with multiple lights which would be great, but this old dog isn't going there, not after all the problems I've had.

[stevebrot]

I have a few odd speed lights for location shots where I don't want to lug studio equipment around. Primarily I used Youngnu with simple wireless triggers and a light meter to set them up, worked well for years. The whole purpose of going with the Pentax flash was to simplify and speed up the process, unfortunately it's not been anything close.

I use mostly Yongnuo speedlights and triggers as well and use my P-TTL Sigma for convenience with on-camera or wired off-camera or as slave to the in-camera flash, but that is all.

Supposedly another advantage of the 360FGZII is the ability to do ratios with multiple lights which would be great, but this old dog isn't going there, not after all the problems I've had.

I did wired contrast control sync with the Sigma balanced against the K-3's flash once, just to see if it works. It did so, and quite nicely, but more involved setups involving optical wireless P-TTL and ratios means just too many very expensive P-TTL slaves, even to test.


Steve

[West Penn]

For off-camera wireless slaves in P-TTL you can use the Yongnuo 585EX and they're selling now for $90 on Amazon. According to Adorama, this flash has been discontinued, however. The Yongnuo can't be used as a controller or master, but they work fine with a AF360FGZ or AF540FGZ (or the Mark II models) on camera as the master/controller. Additionally, the YN585EX doesn't do High Speed Sync..

I have this set-up, so I know it works, but I've not found a real benefit to using off-camera P-TTL. I find that on-camera P-TTL works well enough to very well if the distance to the subject being photographed is changing constantly. In that case, manual flash setting would have to be changed for each shot and that's impractical. If the distance between subject and flash(s) is fixed, manual setting are best option. Also, whenever I'm using flash, the camera is in manual mode.

[C_Jones]

I sold all but one of my Pentax flashes (AF360FGZ). I learned a a lot with them and they performed well, but I decided to switch to the Godox lineup. The Godox flashes I have have built in receivers and act as transmitter/trigger master (on camera) or receiver (off camera). I have the two Godox V1 for Pentax flashes which act as transmitter/trigger or receiver, two Godox AD200 lights (built in receiver) which are for off camera shooting (no on camera), and a Godox AD600 light (build in receiver/cordless). The V1 can control other V1s, control AD200s and the AD600. I also have a Godox XPro-P transmitter which is used on camera to control all off camera lights (Godox). The XPro-P trigger or a V1 for Pentax gives the user compllete control of the Godox off camera lighting. If buying the Godox V1, the Godox V1 for Pentax model would be the one to use with Pentax cameras. The AD200 and AD600 models would either be activated/controlled by a Godox flash such as the V1 for Pentax or the XPro-P as I had mentioned. The batteries used in the Godox lights store quite a bit, and are very reliable. They are cartridge like and come with the lights along with a charger. The amount of bursts I get now as opposed to the AA type batteries is a large improvement (seriously). P-TTL and HSS are available on all of the light products I mentioned, on or off camera. Please note that I am just suggesting this type setup in case you would be interested in a very reliable lighting system. On the other hand, if you are satisfied with what you have for now, this may be just something good to know.

Good luck and happy shooting!

Below are shortcuts to the V1 for Pentax, the Godox AD200, and the Godox XPro-P transmitter/trigger products listed at B and H.

https://www.bhphotovideo.com/c/product/1466064-REG/godox_v1_p_v1_round_ad200...981&

https://www.bhphotovideo.com/c/product/1341870-REG/godox_photo_equipment_ad2...981&

https://www.bhphotovideo.com/c/product/1432377-REG/godox_xprop_ttl_wireless_...981&