differences in metering with different cameras?

sineadw · 12-07-2009 07:35PM #1

Hi all. Myself and Buzz Lightyear did a studio shoot yesterday. We had the lights metered using an external meter and all was looking perfect with Buzz's camera (A Nikon - D60 I think?), yet it was blowing out a bit with mine - a 5D mk I. And on the histogram - not on the backscreen. All other things were the same - ISO, aperture, shutter speed, EFL.. Any idea why this would be? It didn't make that much difference - I just had to stop down on the aperture. I'm just curious as to why thered be as much as a two stop discrepancy in some instances.

waits for 'because canon are crap' comments.. :rolleyes:

kumate_champ07 · 12-07-2009 07:54PM

what kind of metering were u using? perhaps it was spot metering for the external and evaluative for your canon?

sineadw · 12-07-2009 08:02PM

The metering was external - using a separate light meter so we weren't going by the metering on either camera - just what the meter gave both of us, read from each light individually... The test shots were blowing out on me.

ThOnda · 12-07-2009 08:21PM

The lens. You had different lenses with different amount of elements, lenses and thickness of the glass (plastic). Even different amount of transitions from air to lens (and back) causes reflections in which you can loose light.

So you have cheaper lens with less elements or better lens with lenses made from better materials

But I may be more than wrong, of course.

DaireQuinlan · 12-07-2009 08:24PM

That's kinda wierd all right. You'd probably expect a little bit of a differance in practice I guess because of the vagaries of the individual cameras, lens mounted etc etc but it shouldn't amount to anything really noticeable. 2 stops sounds crazy. Did you have exposure compensation dialled in on your camera ? You double checked that everything else was the same between the bodies ? Were you shooting from the same angle ? That might make a bit of a differance to the highlights.

ThOnda · 12-07-2009 08:30PM

Just an idea - if you were shooting closer to the subject, that would also increase the amount of light recorded by the sensor. That would happen if he had used longer focal length than you for the same framing in the viewfinder.

CabanSail · 12-07-2009 08:36PM

Tis is quite a puzzle.

The Exposure Compensation will not affect things as it works on the internal meter, which you were not using.

Both camera's would be set on full manual. The Shutter Speed is irrelevant as the exposure time is set by the speed of the lights. So the only variables are Aperture & ISO.

Two stops is quite a difference, one sensor is seeing only a quarter of the light of the other.

Buzz didn't have a CPL Filter on by mistake?

CabanSail · 12-07-2009 08:39PM

ThOnda wrote: »

Just an idea - if you were shooting closer to the subject, that would also increase the amount of light recorded by the sensor. That would happen if he had used longer focal length than you for the same framing in the viewfinder.

That should not be a factor either as the light meter is reading incident light rather than reflected light.

DaireQuinlan · 12-07-2009 08:39PM

ThOnda wrote: »

Just an idea - if you were shooting closer to the subject, that would also increase the amount of light recorded by the sensor. That would happen if he had used longer focal length than you for the same framing in the viewfinder.

Nah, that wouldn't make any differance. Ideally to meter these things you'd use a flash meter to take an incident reading at the subject position pointing toward the camera. This is your metering for that point regardless of whether you're 1 foot or 10 feet away.

ThOnda · 12-07-2009 08:45PM

Let me disagree. The light goes from the source to the object. And is metered there. And then it is reflected and goes to the camera. And still, the light is receding with the root of the distance also between the reflected surface and the camera.

The CPL is also good hint, never thought about it (not having CPL for any of my recent lenses).

DaireQuinlan · 12-07-2009 08:50PM

ThOnda wrote: »

Let me disagree. The light goes from the source to the object. And is metered there. And then it is reflected and goes to the camera. And still, the light is receding with the root of the distance also between the reflected surface and the camera.

Trust me, thonda, that's not the way it works. Just as an experiment, try spot metering a wall across the room from you. Now walk up to the wall and spot meter the same place. You'll get the same reading. By your theory above you ought to get a higher reading the closer you get to the wall.

DaireQuinlan · 12-07-2009 08:55PM

I got it ! Everytime sinead went to take a shot, buzz stood in front of one of the lights :-)

nilhg · 12-07-2009 08:58PM

sineadw wrote: »

Hi all. Myself and Buzz Lightyear did a studio shoot yesterday. We had the lights metered using an external meter and all was looking perfect with Buzz's camera (A Nikon - D60 I think?), yet it was blowing out a bit with mine - a 5D mk I. And on the histogram - not on the backscreen. All other things were the same - ISO, aperture, shutter speed, EFL.. Any idea why this would be? It didn't make that much difference - I just had to stop down on the aperture. I'm just curious as to why thered be as much as a two stop discrepancy in some instances.

waits for 'because canon are crap' comments.. :rolleyes:

Just trying to think this through, you say the EFL was the same, so both cameras were side by side with lenses set to give the same field of view? That would rule out ThOnda's theory. I'm just wondering if any sort of in camera processing could account for the differences? A side effect of something like Nikon's D Lighting?

It would be interesting to see the images with full exif.

sineadw · 12-07-2009 09:00PM

Nope - no CPL, all manual and we were both using decent primes so I can't see the lenses making any real difference even if that were to be a factor. Odd, huh?

I thought maybe there'd be a bit of a difference in the sensors, but I was surprised at the different light getting in. It seemed to be my body that was at fault too - buzz's was spot on with the metering for the lights. I've never had a problem in the studio before though?

Buzz Lightyear · 12-07-2009 09:01PM

sineadw wrote: »

(A Nikon - D60 I think?)

D80 actually

. Either way we were both shooting manual. The light meter gave us a reading of say f8 for the subject. I dialed in F8 and got a correctly exposed image, however Sineads D5 was being blown out by the same settings. Very bizare ! She ended up shooting at about F11 to achieve the same on screen exposure as myself. Her ISO was equal, as was the shutter speed.

So on manual there should have been no difference - except if she had dialed in exposure compensation at some stage, which with it not being my camera I couldn't immediately tell.

Daire - shooting from the exact same spot.
Cabansail - As for a filter - I was shooting mainly with my 50 without a filter, however it was Sinead who was getting blown.

sineadw · 12-07-2009 09:02PM

nilhg wrote: »

Just trying to think this through, you say the EFL was the same, so both cameras were side by side with lenses set to give the same field of view? That would rule out ThOnda's theory. I'm just wondering if any sort of in camera processing could account for the differences? A side effect of something like Nikon's D Lighting?

It would be interesting to see the images with full exif.

Mine's full frame, but I was shooting with longer lenses. We were both shooting raw so nothing in camera should have impacted that much? Am I right there? Don't know what D lighting is...

sineadw · 12-07-2009 09:13PM

Don't think I can dial in exposure compensation in Manual Mode?

kumate_champ07 · 12-07-2009 09:24PM

ThOnda wrote: »

The lens. You had different lenses with different amount of elements, lenses and thickness of the glass (plastic). Even different amount of transitions from air to lens (and back) causes reflections in which you can loose light.

So you have cheaper lens with less elements or better lens with lenses made from better materials

But I may be more than wrong, of course.

the rated f stop for each lens would take that into account wouldnt it? or is the f stop just the size of the aperture/diaphragm relative to the focal length and not necessarily exactly how much light is transmitted thru it?

ThOnda · 12-07-2009 09:29PM

F-stop is just geometrical value, not considering optical properties of the materials of the optical elements.

Buzz Lightyear · 12-07-2009 09:41PM

ThOnda wrote: »

F-stop is just geometrical value, not considering optical properties of the materials of the optical elements.

F-stop maybe only a geometrical value, however unless you've bought your lens from Penny's or Dunnes Stores, they should be calibrated to allow a certain amount of light through the opening (aperature). So unless Sinead's Canon lens's were a monday morning jobbie, I can't see that being a factor ...

kumate_champ07 · 12-07-2009 09:47PM

DaireQuinlan wrote: »

Trust me, thonda, that's not the way it works. Just as an experiment, try spot metering a wall across the room from you. Now walk up to the wall and spot meter the same place. You'll get the same reading. By your theory above you ought to get a higher reading the closer you get to the wall.

that would explain how we dont have total darkness being so far away from the sun!

kumate_champ07 · 12-07-2009 09:51PM

have you had the 5d long? the jog wheel at the back might be set for exposure compensation. u can accidentally rub off it and change the settings. there should be a custom function to switch it off

if u both had f8 and f11 then thats only 1 stop off?

CabanSail · 12-07-2009 10:31PM

Exposure Compensation is an offset to the Metering in the camera, so as neither meters were being used it cannot be a factor.

The Nikons have 200 ISO as minimum (but you can reduce that down to 100 ISO)
The Canons have 100 ISO as minimum.

Are you sure both ISO's were the same?

Buzz Lightyear · 12-07-2009 10:44PM

CabanSail wrote: »

Exposure Compensation is an offset to the Metering in the camera, so as neither meters were being used it cannot be a factor.

The Nikons have 200 ISO as minimum (but you can reduce that down to 100 ISO)
The Canons have 100 ISO as minimum.

Are you sure both ISO's were the same?

My D80 has ISO 100 as min and was set for that and correctly exposed. I know Sineads 5D was set the same. It has to be a custom setting somewhere - only I don't know the Canon kit.

I know on the D80 you can set the exposure comp even when in manual. Sinead's checked her users manual and it's not possible with the 5D

Confusus still reins

kumate_champ07 · 12-07-2009 10:46PM

CabanSail wrote: »

Exposure Compensation is an offset to the Metering in the camera, so as neither meters were being used it cannot be a factor.

so if u use full manual and enter the shutter speed u cant use exposure compensation also? i know it wouldnt be done but cant the setting be changed while in manual mode?

AnCatDubh · 13-07-2009 12:38AM

Go back to the quality of the lens (glass/plastic/optics/construction) for a minute - anecdotally and without as scientific a setup as has been posted here, I have found a significant difference between two lenses which I have - different brands. With same camera at f2.8 on both, and identical settings in so far as I can remember - IIRC the shutter speed drops significantly on one. One's a Tamron, the other is a Pentax prime. The Tamron drops the shutter speed. I always assumed it was the quality of the Pentax over the Tamron.

sineadw · 13-07-2009 07:44AM

I was using the Canon 85mm 1.8 USM, the Canon 50mm 1.4 USM and the Canon 135mm L, so no problem with quality. And nope - you can't use exposure compensation in manual mode - moving the wheel just changes the aperture. Manual is manual on the 5D - changing the settings simply changes the shutter speed or aperture.

100 ISO *definitely* - I can drop to 50 though

AFAIR (and I may not be remembering correctly - we were shooting for 11 hours all told :eek: ) the differences seemed to grow more when the lights were toned down and we were working with a higher aperture. So one stop difference when I was up around 11 or 16 but almost two stops when Philip was down at 2.8. Philip am I remembering that correctly?

Its all just out of curiosity really.. I'm happy with the shots. We can't put them up for comparison as yet though as they're for an album cover and the client has asked us not to publish anything until it's released..

DaireQuinlan · 13-07-2009 09:18AM

Buzz Lightyear wrote: »

F-stop maybe only a geometrical value, however unless you've bought your lens from Penny's or Dunnes Stores, they should be calibrated to allow a certain amount of light through the opening (aperature). So unless Sinead's Canon lens's were a monday morning jobbie, I can't see that being a factor ...

I used to think this aswell. We had some discussion about this ages ago here. Look up the difference between F-Stops and T-Stops. F-Stops are purely geometrical. T-stops are f-stops with the transmissive quality of the lens taken into account. T-stops are used in the film and motion picture industry (I think it was Hugh_C who illuminated the issue originally, he's got a background in the film industry IIRC). With modern lenses its not really an issue any more. I think the conclusion was that modern zooms don't lose anything more than maybe 1/3rd of a stop, primes even less, so in practice its not really anything to worry about. In any case the lenses on each of the cameras would be affected similarly.

DaireQuinlan · 13-07-2009 09:29AM

Actually, I'd be interested in seeing what would happen without the added variable of having strobes going off. IE take a meter reading with the external meter in daylight and take the shot with the metered readings and see what the exposure is like.

Morrisseeee · 13-07-2009 09:32AM

One was a Nikon and the other was a Canon, so they're bound to disagree !!! :pac::D:p

stcstc · 13-07-2009 10:03AM

does the D80 actually do iso 100, some of the nikons start at 200 and have a approx for 100 in lo1 i think its called

It not something like that that causeing it is it?

differences in metering with different cameras?

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