Beginner Odd metering discrepancy between liveview and view finder with ND grad

[Fussyfez]

Wasn't sure where to put this...

I have a canon 600d and yesterday bought a hama ND vario. I'm currently having a little play, and have noticed a metering difference between the two viewing modes.

Whilst at the lightest setting on the ND, liveview reads 1/3rd of a stop over the view finder, and with the ND at its darkest, live view is about 5 stops over what view finder metering is saying.

The live view metering is much closer to correctly exposed, with a viewfinder metered shot being under exposed.


I've re-read that and it doesn't make much sense so here's an example.

Compose shot in live view manual iso 400 (I'm doing this as we speak)

F5.6 / 6 seconds gives a perfect exposure according to the meter, now got live view button to enter view finder mode, half hold shutter to trigger meter, and it says the photo will be 3 stops over exposed, recommending 2 seconds / f5.6, which will come out under exposed.

Hope that's clearer.


Any ideas why this might be happening?

Is it just a case of playing with the ND for best results and just using liveview for metering/composure as they will all be tripod landscape /water /clouds etc anyway?

Thanks.

 

[HoppyUK]

Could be light entering the viewfinder, skewing the non-live view reading. Canon provides an eye-piece cover for this as the meter lives in the pentaprism and is easily influenced by viewfinder light. Use it during the actual exposure too.

 

[MarkLG]

I suspect the meter in the pentaprism which is used in normal viewfinder mode is struggling to get an accurate exposure at very low light levels. With a fixed value ND you'd just meter without the filter and work out the correct exposure with the filter from there. Probably not possible on a variable ND unless it's accurately marked.
In live view the camera will be metering off the image sensor itself which seems to cope better with the low light level and can still get an accurate reading. I've use NDs upto 10 stops on mirror less bodies which only have live view mode and found the metering to be very accurate.

 

[Fussyfez]

Thanks guys, I'll have a look for the view finder cover but I'll test tomorrow just blacking it out.

 

[Brian G]

I did a back to back test using my ND3 filter on my Canon 6D and on a 25 second exposure in bright conditions there was no difference between the eyepiece covered or not covered.

 

[HoppyUK]

Thanks guys, I'll have a look for the view finder cover but I'll test tomorrow just blacking it out.

The viewfinder cover is primarily intended for tripod use, ie when you don't have your eye to the viewfinder to shade it and the camera is in an auto exposure mode. Light will get in and upset the meter and hence the exposure.

With a strong ND filter, the problem is different and it's light coming through the viewfinder and then finding its way around chinks in the mirror mechanism, mainly around the piggy-back mirror that is used to direct light to the phase-detect AF sensors in the base of the camera. This miniscule amount of light is normally insignificant, but with say a ten-stops ND filter fitted, light coming through the lens is reduced by 1000x and in that situation the miniscule amount of light creeping around the mirror becomes a noticeable proportion of the exposure. Some cameras are worse than others, but they all do it.

Edit: a quick google search for examples, this is typical http://scottreither.com/blogwp/2012/07/01/nikon-d800-e-long-exposure-issues-problems-2/

 

[Pookeyhead]

Live view on many cheaper cameras does not stop down the lens, and will automatically adjust the live view image. It often bears no resemblance to the exposed image you get. It's usually just used as a electronic viewfinder in cheap cameras, not an accurate preview of what you will get. Live view also cripples the camera's AF abilities as it drops back to a contrast based system, and also, because your mirror is up, it uses a crude metering system that measures light reflecting off the sensor surface.

Quite simply... stop using live view. It sucks. I use it to manually focus accurately, and to frame sometimes... yes... but drop out of live view to meter, and if using AF, focus, before taking the shot.

 

[Brian G]

An ND3, 10-stop filter, is too dense to see anything through, so you would normally frame the scene and then add the filter.
I find on my 6D, that even with the ND3 in place you can still get a good image in Live View, so you can at least check the framing.
When I'm using my ND3 I always set everything manually, including focus.
I always take a range of bracketed exposures too, and certainly don't rely on the camera to meter with the filter in place.
What I usually do is meter the scene without the filter and then make a rough exposure calculation based on the filter density. Having added the filter I know I need an additional 10 stops of exposure, and I base my exposures on that, although obviously, with a variable filter you don't know exactly what the equivalent filter density will be.
Hence, it's a good idea to either bracket, or at least take a test shot and review it.

 

[HoppyUK]

Live view on many cheaper cameras does not stop down the lens, and will automatically adjust the live view image. It often bears no resemblance to the exposed image you get. It's usually just used as a electronic viewfinder in cheap cameras, not an accurate preview of what you will get. Live view also cripples the camera's AF abilities as it drops back to a contrast based system, and also, because your mirror is up, it uses a crude metering system that measures light reflecting off the sensor surface.

Quite simply... stop using live view. It sucks. I use it to manually focus accurately, and to frame sometimes... yes... but drop out of live view to meter, and if using AF, focus, before taking the shot.

Disagree. Live view is my preferred method when the camera is on a tripod, as it always must be when using an extreme ND filter. The only exception to that is when it's hard to see the LCD properly, such as shooting into bright light.

To say that live view cripples AF is not really true. Sure, the camera switches to contrast-detect AF and that is much slower, though that's not a problem with tripod working and it's extremely accurate - with the magnifier and ability to scroll around the screen, you can focus on anything with great precision.

Exposure should be the same as normal metering, as it reads the actual image on the sensor. There's nothing crude about live view metering, and it's not reading anything reflected from the sensor surface. With extreme NDs though, good exposure can be unpredictable, eg with a ten-stopper in place, that can be asking a bit much of any metering system - it might be accurate, it may not be; a ten-stop filter will not be exactly ten stops, they all vary a bit and also some brands vary from batch to batch; infrared suppression varies so exposures can go up and down a bit according to how much IR light is around. Basically, make your best estimate and then be prepared to adjust as necessary, with reference to the histogram and blinkies (highlight over-exposure warning) rather than how the LCD image looks.

 

[Pookeyhead]

Disagree. Live view is my preferred method when the camera is on a tripod, as it always must be when using an extreme ND filter

I'm not referring to using live view to get a visual idea of where your grad is placed,(although why you can't do that through the viewfinder I've no idea) I'm referring to using live view throughout the whole process. Metering with live view is NOT using the camera's full metering capabilities: You can not use spot or centre weighted in most cameras while in live view, and are limited to a fairly crude evaluative system that is NOT as sophisticated as using TTL metering. You've paid for that metering sophistication, why not use it? Also, many cheaper SLR can do NOT stop the lens down when aperture is adjusted when in live view, so you wouldn't get an accurate preview of your grad anyway, as the lens will be wide open.

You're talking about landscapes and studio though. I've seen people using their cameras in all manner situations in live view, including AF and metering. Your AF is slow, and your camera's TTL metering is being by-passed. Why would anyone want to do that? Why bother buying a DSLR?

To say that live view cripples AF is not really true.

Yes it is. It's slow, hunts around, and is not as accurate. Why would you want to by-pass the camera's phase detection AF in live view? It is not as good in live view. That's a fact.

Live view is an alternative working method designed for when you can't get your eye to the viewfinder, not how you should be using your DSLR 24/7. I agree it's very useful for landscape.... but I'd still be metering with TTL for accuracy.

Sure, the camera switches to contrast-detect AF and that is much slower,

In what way is that not crippling your camera's AF abilities?

though that's not a problem with tripod working and it's extremely accurate - with the magnifier and ability to scroll around the screen, you can focus on anything with great precision.

A) It's NOT as accurate, unless as you say... you zoom in... and if you're going to do that, why bother using AF at all? Just manually focus. Manually focusing on a zoomed in live view probably the most accurate way of focusing. Anything other than landscape though, and live view focus is utter sh*t.

Exposure should be the same as normal metering, as it reads the actual image on the sensor. There's nothing crude about live view metering,

In ever DSLR I've used, you're limited to a very basic evaluative metering system. No spot, no RGB capability, no centre weighted. In fact... no ability to switch metering modes at all. Why do this? Why not meter before you drop into live view then you can spot meter, which is incredibly useful in high contrast situations. Better still.. if you're at all bothered, use an incident meter?


Plus... don't forget what I said earlier. Most lower end cameras are live previewing at wide open aperture only, so your still not seeing an accurate preview anyway, and most cameras lock out the DOF preview when in live view. basically... on many low end SLRs you've no real way of previewing DOF in live view at all.

 

[HoppyUK]

David, despite the thread title, the OP is not talking about ND Grads, but a Hama Vario ND filter, with six seconds exposure time, on a tripod, for landscape. And as you say, live view is "very useful for landscape...."

 

[Pookeyhead]

. And as you say, live view is "very useful for landscape...."

...but sh1t for metering and AF. So long as you know this FACT...


That is all.

 

[Blank_Canvas]

I have always used the viewfinder and still prefer it even today. LCDs and liveview didn't exist when I picked up my first camera. I just meter the scene, add the ND filter. If I'm using a linear ND I will also just check it using the DoF preview button ND and calculate the exposure adjustment in my head.

Don't get me wrong Liveview is very useful in some situations and the articulated screen on X-T1 is very handy for some low level shots or if photographing over an obstacle. However the LCD is useless in bright light. I personally prefer the viewfinder - it's all horses for courses.

 

[Pookeyhead]

Don't get me wrong Liveview is very useful in some situations.

Agreed. I'm not anti-live view. I just think people need to be aware that A) they are not using the super duper AF they paid for, and B) they are not using the super duper metering they paid for. So long as you know that.. as many do not realise this. This was the purpose of my post... simply to enlighten those that thought the camera used the same AF and metering systems as it does out of live view.

Live view is incredibly useful, yes.

 

[HoppyUK]

...but sh1t for metering and AF. So long as you know this FACT...

That is all.

Agreed. I'm not anti-live view. I just think people need to be aware that A) they are not using the super duper AF they paid for, and B) they are not using the super duper metering they paid for. So long as you know that.. as many do not realise this. This was the purpose of my post... simply to enlighten those that thought the camera used the same AF and metering systems as it does out of live view.

Live view is incredibly useful, yes.

So is live view 'sh1t' or 'incredibly useful'? Hand-held, I would say sh1t, but on a tripod with fairly static subjects, live view is usually my preferred mode.

Live view focusing is slow for sure, but it is versatile, precise, and very accurate. I use both live view AF and manual, always with the magnifier. Live view is also excellent for checking depth of field with the lens stop-down button, unlike the viewfinder that doesn't show DoF accurately at f/numbers lower than about f/2.8, and is hopeless at high f/numbers because the image is too dark to see much of anything at all.

Live view metering is definitely not sh1t, and neither is it the crude system you described - rather the opposite. It even provides a live histogram, and on some cameras you also get live highlight blinkies, shadow blinkies, and zebras, plus a ton of other useful info if you want it. I use evaluative 99% of the time anyway as it will always get you pretty close, then for tricky subjects adjust with reference to the histogram and blinkies. It's not fast, but there is no better method than that.

 

[Pookeyhead]

So is live view 'sh1t' or 'incredibly useful'?

Sh*t if you use it as the de facto way of shooting in all situations, and useful for things like fine manual focusing, or framing in dark conditions.