Originally posted by A there are two parts to this.
I think the issue is that in certain exposure conditions TTL is not as accurate because after the flash there is still ambient light which can lead do over exposure in some cases. Also TTL requires a separate flash sensor, and inout channel. P-TTL uses the main metering system and is therefore cheaper.
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Not correct with TTl and ambient light when you set up to shoot a photo the ambient its taken into consideration by the camera and a lesser amount of flash is provided by the flash this usually is done in aperture or manual modes with the digital cameras they no longer provide this ability unless in full manual mode the result is for example at a wedding you want to capture a room full of people with the bride and groom you would set your camera to 30-125 shutter speed and a F3.5 this will capture the main subject with the flash at a lower intensity and the ambient light will allow the rest of the people to be exposed and because a low shutter speed is used the amount of over exposure would not occur why? because its practicly impossible to over expose film at night unless the interor lighting is too bright. I also do long exposures at night with digital without overexposure. TTL actually measures the ambient light then caculates the amount of additional light required by the flash. This is why TTL was so good.
The reason over exposure occurs with flash is because program mode is used which reduces the the ambient light as the aperture is heaps smaller and a full flash of light is displayed on the finish product this happens to beginners and and people that want to play the safe game. This P-ttl stuff it is all new to me I've only learn't it exist the last few days but TTL I won awards with it because I understand it and how it works. Now I have to learn P-ttl See my Pentax istd has ttl and last year I got a K-m and it doesn't have TTL so now I have to learn it.
The fact that digital sensors read extra light is mostly incorect as the new lens are coated with a metalic coating to reduce flare so sensors are also not an issue.
Years ago I had a flash that metered its own light and when taking a photo of the sunset with subjects in the fore ground I would have to put tape over the sensor that read the light because as soon as I took a photo the flash would switch off and leave me with an under exposed photo because the sunlight was switching my flash off hence the tape over the sensor took a few sessions to solve that issue. This was pre TTL. I think I might still have that flash could be handy.
Looks like P-ttl controls the F stop and the flash blast taking control away from the photographer even though the shutter speed is set by the flash. I think we need a camera where the photographer can set the F stop setting which controls the flash and measurers the ambient light because ambient light is currently ignored by P-TTL hence a exposed person and a black background. Mabye some clever dick used the ambient light factor in a misleading way when premoteing digital cameras hence eneryone thinks abbient light is being measured when in fact its only being dealt with by cutting it out by using smaller apertures. So looks like I am starting to get my head around this. We need better digital cameras these aren't good enough.
---------- Post added 11-13-17 at 10:01 PM ----------
Bring back TTL
Haven't tried this yet but I think the further away from you subject the better the lighting from your flash will appear. as this will open your aperture bigger which will let in more light and may also reduce the flash required however it may or may not wash out items closer than your subject but to be honest I have a feeling it won't because I think its still the same metering system but the control have been given to the camera and not the photographer hence the requirement for it to know / set the F stop. If we can make the camera change the f stop possibly by moving away we regain some control. But there is the full manual mode which will not let us down i hope. Well I better go test these new theories now.
I think also the 1.5 factor with DSLR's over 35mm helps with the reduced over exposure with flash as we are 50% further away when taking photo's now which should have opened the aperture a stop or 2 causing less flash on the subject as the subject is further away.
Most of above was based on 200 iso with 080c ring flash Just shot off some around the house with my in camera flash on the K-m and I found opening the ISO to 800 introduced extra ambient light and I figure it either opens the aperature or extends the shutter timing I went from 200 to 800 iso that is 2 stops now I have no idea where these two stops were gained but when I added 2 stops to the exposure before increasing the ISO next to no change was gained so I think somthing weird is going on here because all settings are a stop apart. any way a great improvement in light indoors when increasing iso. I am going to have to try that on the ringflash. Hope you guys don't mine me experinenting with my thoughts here. I guess the change in ISO makes the sensors more receptive to light as the shutter speed would remain the same in flash mode and the aperture should be two stops down.
Wish I had of kept my interest up in photography after going digital as back when film was around we didn't have the advantage of changing the ISO each shot as it would have meant changing the roll of film over. so this is definitely a plus over film. It was the flash problems that really discouraged me and the fact that I don't believe photo's should be edited beyond a touch up. They never look right there is always a flaw even if only the photographer know's it it's still there. Most mistakes are with lightening and colour and to me they look awful but to the public their beautiful.
Last edited by Kombivan; 11-13-2017 at 11:46 PM.