Please Help - D90 + Sigma 28-70mm F2.8DG....very strange results.

[mikeyw]

Guys,

I took my new D90 out today with the Sigma 28-70mm F2.8 that i'll be mainly using on it but was very deflated when the camera seemed to have a mind of it's own at times

I'm familiar with Nikons having shot a D40 for a couple of years but I think the multi-metering, multi focusing might be getting the better of me - either that or the lens or body has a fault.

The gist of the problem is that using A mode (which often do) or P mode (occasional) the camera seemed to be choosing ridiculously fast speeds...far too quick to let enough light in, noticably so indoors without flash. I like to shoot F2.8 indoors and let the camera chose the speed / iso and would normally expect 1/30 or 1/40 but the D90 was wanting to shoot much quicker giving underexposed results.

Here's some examples (excuse the crap pics - I was just collecting examples of the problem) :-

A mode F2.8 - Camera selected 1/4000th....far too dark

Tried again this time it choose 1/100th but focus appears to have locked on the bldgs behind

Indoors set to A mode F4...bit soft but lighting is correct...camera used 1/50th which is as i'd expect

Tried again this time it somehow decided I needed 1/400th !!

Another at F3.2 in A mode - camera decided it needs 1/2000th !!

Outdoors at F5 - again opts for 1/4000th

Finally when I got in to check the lens wasn't playing up I popped it on the D70s

Indoors at F2.8 in a darkish area....pretty much on the money light wise by the D70

Again the D90 is way off with the same lighting and lens :-

I'm really confused and to make matters worse as you zoomed in / out on the lens you could see the camera switching between shutter speeds it should have been using low light indoors ie 1/50, 1/60 to ones it shouldn't ie 1/500 1/1000th.....almost as if something was throwing it.....even down to the connection between lens and body....

I think tomorrow a hard reset on the camera is needed and I start again but i'm very confused at the moment as I love to shoot in A mode and at the moment it's a lottery whether to D90 makes the right choice or not regarding to shutter speed to match the aperture.

Sorry for going on but if anyone has any thoughts i'd love to know....I can only put it down to the complex multi focusing / multi metering

TIA
Confused Mike.

 

[wack61]

Is the ISO set to auto, if so set it to 100 to remove one of the variables, does it do it with any other lenses or just the sigma

 

[mikeyw]

Left ISO at Auto but i think i've found the problem. Either fully zoomed in or at the widest the camera gets confused and up the shutter speed too high, just by moving it slightly inside the extremities it gets it's brain back and the shutter drops to sensible levels.....tried this on the indoor shelf shot and it reduced it from 1/125th to 1/30th just by moving the lens very slightly off max zoom........very weird but it looks like the reason.

Need to do some more tests tomorrow as i'm sure was still seeing this behaviour inside 28 & 70mm

 

[puddleduck]

I'd suggest making sure your D90 isn't in bracketing mode?

 

[mikeyw]

Will also do some further testing with Nikon 18-55 tomorrow

 

[mikeyw]

I'd suggest making sure your D90 isn't in bracketing mode?

Yeah that did trip me up on the first day but turned that off now

When doi people use bracketing ? - Be good for landscapes to get the sky & land metered properly but any other uses ?

 

[TG.]

Yeah that did trip me up on the first day but turned that off now

When doi people use bracketing ? - Be good for landscapes to get the sky & land metered properly but any other uses ?

HDR photos

 

[foodpoison]

I bracket with film.
That's it though.

fingers crossed you get this sorted mate! Not cool!

 

[mikeyw]

Had some more tries this morning and seems to be getting better - Moved to centre weighted meter / focus and this seems to help (obviously better for portraits)

Still far from convinced - my mate has a D200 so taking the sigma there tonight to test

 

[MJ Stebbings]

Try using manual settings.
And are you exposing off the same thing every time?
What exposure setting are you using? Try using centre weighted and use the same area to expose for a couple of shots along with choosing centre AF point and see if that helps.