Different cameras - different light readings?

I was helping out on photoshoots for a brochure yesterday.  The first was an apartment.  I took a shot looking towards the window to get an idea of what shutter speed I would need to use to get the exposure right with an aperture of f8 and Bowens units.  The other photographer asked me for my settings as a guide - shutter speed, aperture and ISO, in manual mode - were given and she took a shot.  Her shot came out about 2 stops overexposed.
We checked the histograms and they confirmed it.

We were up against the clock so couldn't delay to figure it out and so made our necessary adjustments but it's been bothering me since.

There is a possibility that she wasn't using manual mode but I don't think so.  I've heard of differences in exposure results between different makers but are there different results between cameras from the same maker or am I completely off my trolley?   

There can be variations of exposure between lenses from the same manufacturer about 2/3 of a stop I have heard of.

2 stops seems excessive even between manufactured IMO

Was one a Nikon body and was the ISO 100? 

B

Thanks Brendan,
Hers was a Canon EOS 30D, mine a 5D MkII.
We were both using wide angle lenses - mine was an 11-18mm.  Not sure what hers was.
Paul T.

Hi Ross,
Unlikely as she asked me for the three settings.  On top of that she didn't want to go higher as she would get a lot more noise than I would.

I guess at this stage I should see if she still has the RAW files and check.

Paul T.

There are differences between cameras, between manufacturers and indeed bewyeen lenses. Some hand held meters allow you download specific camera profiles to them to allow you "calibrate" your meter to your specific camera. But two stops in the difference definitely suggests user error to me.

Suggest you check the EXIF on both photos to confirm.

That will eliminate (or confirm !) the possibility of user-error.

Thanks guys again!  Ross, we hadn't fired the flash units at this stage.  This was simply getting the exposure right for the windows and
then adding the flash later for the room.

I expect it's something stupid that I/she missed and we didn't have time to investigate - it was all very hectic!

Thanks for all your replies.  I'm trying to get her data from her.  Once I get something I'll post it here.

Paul T.

Lot's of useful information provided above, but one thing I haven't seen mentioned yet in relation to the lenses is the lenses maximum aperture. If both of you were using zoom lenses and both of the zoom lenses had variable maximum apertures, this may have been a factor in the exposure difference, particularly if setting the exposure manually. But without more details, I'm only guessing.

Well .................
I got the file from the 'lady' and I've put it with my photo and the result is below:



The EXIF data is identical with respect to shutter speed 1/50s, aperture f8 and ISO 1000.
I think I would concede that the difference may not be as severe as I originally thought but it still seems a lot to me.

Paul T.

Quite a considerable difference indeed, but as you point out now, certainly not 2 stops. I'm afraid the images, even with embedded EXIF don't tell the whole story as there are still many factors which can effect exposure.

JPG conversion - if you're shooting JPG, your camera will typically apply a curves adjustment and indeed can also change exposure, which can lead to a discrepancy. Similarly when converting, your WB choice can also effect exposure, even as much as a stop depending on the choice and the colours in the scene.

As Thorsten pointed out, the lens can also play it's part (I mentioned this at the tutorial acutally!).

If you had the two RAW files, I'd certainly be interested in having a look to satisfy my own curiosity?

Hi Ciaran,
I'll put the two raw files on my website and give you access.  My ISP only appears to want to allow me send e-mails - a restriction on the attachment sizes that I can't get them to tell me.

Thanks,
Paul T.

I'm not familiar enough with the 5D MkII to comment on this, so I'll ask a question instead. Does highlight priority also affect manual exposure images? From what little I know, I presume it does as it's something that alters the raw image data by the Digic processors before the file is finally written to the memory card.

Nope, the highlight priority was disabled.  I used to turn it on but I felt it was heading towards an automatic setting and, being a control freak, turned it off.  I just checked it though!  Good call.
My Internet connection is slow so I'm letting the RAW files find their own way to my website while I go to bed.

Cheers guys,
Paul T.

It's an interesting one alright.. first off, something seems to be going on in your RAW conversion. When I convert both to JPG, applying no additional settings to either (i.e. no contrast, brightness, exposure settings), I get very different images to you. Whilst there is still a difference between shots, it's even less pronounced again than you have shown.

As Thorsten has also pointed out, both lenses also have different maximum apertures, one being f4 and one f4.7. One other possible reason is simply the change in ambient light over time.. I know your clocks weren't synced, but between these shots, according to the time stamps there is almost a 5 minute difference. 

Maybe the viewpoint also playe a small part? One image has a considerable amont more white wall in the shot than the other, so will receive more reflected light?

Using the white wall in the background as the reference point, I reckon there is only a 1/3rd of a stop difference between both images.

Thanks guys for all the energy that went into answering my 'curiosity' question.  In reality there was only seconds between the shots but maybe that was all that was necessary.  The difference was very apparent on the camera displays but then I would expect that.  It was the amount that caught me and I seem to remember that her highlights were overexposed.

I have a 40D and a 10D as well so when I have a spare hour I'll set up the 3 cameras in a controlled condition and take a shot with each of the same setup and see what unfolds.

Thanks again for taking serious amounts of time out to look at this.

Paul T.