Why not wide open in P mode with flash?

Ben Taylor

New member
If I want to force use of the built in flash ( to fill in dim subject against bright background ) I can use P mode and it will use a shutter speed between 60th and 200th to ensure the flash fires.
That works great outdoors in daylight.

However in a dim environment, in P mode with the built in flash popped up, it uses f7.1 or f8 and cranks up the ISO really high, say, 4000. (Without the flash, it shoots wide open and ISO above base but as low as it can get away with, say, 1250.) Why doesn't it open the lens as wide as possible and keep the ISO as low as possible with tree built in flash?
 

nickt

Senior Member
Auto iso with flash doesn't always do what you might think it should. It behaves differently on different Nikon models and might be different with internal vs external depending on the model. You could turn off auto iso and still use P or you might just as well use aperture priority. Manual mode might be better. Aperture mode probably will give you 1/60 second when you pop the flash up and maybe you want a little faster.
There are several threads here on auto iso and flash. Try this one:
https://nikonites.com/flashes/35340...-shoe-ttl-flash.html?highlight=auto+iso+flash
 

Ben Taylor

New member
Ok, interesting that auto ISO doesn't behave as expected and thanks for the link, but that can be eliminated.
(For the following test I have the 24-85 f3.5-4.5 on, zoomed right out thus wide open is f3.5)
Turning auto ISO off and just setting ISO to 800 in a (very) dim room, without the flash it meters at f3.5, 1/6th. But pop the flash up and it meters at f5, 1/60th, and underexposed. Can understand 1/60th as that is the minimum shutter speed with flash setting, but why f5 target than f3.5 if underexposed?
The conclusion I'm drawing is that P mode is not good in dim light and is only really useful when you want to limit
the amount of light coming in and you want tree camera to choose the combination of narrowing of aperture and shutter speed do it by. But other interpretations welcome...

I'm quite aware also that some people's natural instinct is to set ISO manually, possibly because they use/used to use film cameras, whereas another school of photographer the ISO is last on the list of the variables they want to set themselves. I come in the latter camp. I always read the exif on Flickr and you often get photos with unnecessarily fast shutter speed, say a2000 th for a still portrait, but higher than base ISO. The only possible reason is the photographer has set ISO manually I guess? This is one reason I like nikons max ISO/ min shutter speed settings.
 

Ben Taylor

New member
Ok thanks for the suggestion, and link -however, I can eliminate auto ISO from the problem.
If I set it to a specific high ISO with auto ISO off in a very dim environment, then with flash off it meters to wide open and a fairly slow shutter speed. But with flash popped up, it meters to a a narrower aperture i.e. not wide open, and underexposed.
 

Ben Taylor

New member
Also potentially a different problem but similar- the fill flash was a bit hit and miss today- when I was shooting some people standing on the doorstep of a building from inside the building and it was bright outside, I locked AE on one of them and then focus and re composed, and annoyingly the flash didn't fire, and the people were far too dark. This was 1/125, f5.6, ISO 100 (auto), spot metering (AE locked on someone's face), P mode, 24-85 f3.5-4.5 at 24mm.
Similar situation where they were sat under a shady tree (as was I) and it fired most of the time.
Any ideas as to any reason why the fill flash might not work?
 

Bikerbrent

Senior Member
Welcome aboard. Enjoy the ride.

It has been my experience that P mode does have some issues in tricky lighting and flash conditions. I would recommend trying Aperture, Shutter, or full Manual mode and see if this doesn't help.
 

Horoscope Fish

Senior Member
Also potentially a different problem but similar- the fill flash was a bit hit and miss today- when I was shooting some people standing on the doorstep of a building from inside the building and it was bright outside, I locked AE on one of them and then focus and re composed, and annoyingly the flash didn't fire, and the people were far too dark. This was 1/125, f5.6, ISO 100 (auto), spot metering (AE locked on someone's face), P mode, 24-85 f3.5-4.5 at 24mm.
Similar situation where they were sat under a shady tree (as was I) and it fired most of the time.
Any ideas as to any reason why the fill flash might not work?
Based on your description it sounds like Program mode is having difficulties when the dynamic range of the scene is extreme. I agree with the suggestion to take control of the situation by using aperture priority, shutter priority or manual mode instead of Program. Using the Exposure Compensation function might help, but I'm not sure it's available when in Program mode.
 
Top