Thanks neuro, I knew I could count on you for a great response! Good info, I find the evaluative metering using only one AF point very interesting. Sounds kind of like roulette...you never know which point you're gonna get for the exposure. [:O]
Thanks neuro, I knew I could count on you for a great response! Good info, I find the evaluative metering using only one AF point very interesting. Sounds kind of like roulette...you never know which point you're gonna get for the exposure. [:O]
R6 II --- RF 14-35mm f/4L IS --- RF 24-105mm f/4L IS --- RF 100-400mm F5.6-8 IS
70D --- EF-S 10-22mm f/3.5-4.5 --- EF-S 17-55mm f/2.8 IS --- EF 70-200mm f/4L IS --- EF 85mm f/1.8
Originally Posted by Carlos Lindado
Hi Alex,
Could the problem be due to light entering the viewfinder from the rear of the camera?
When you use LiveMode, you obviously have to take your face away from the viewfinder to view the LCD Screen. This lets more light in through the back of the viewfinder and therefore the camera thinks it has more light then it really does have in front of the lens, so it under exposes. Try your experiment again with the tripod, but use the viewfinder cover on your neck strap and test it again.
I know it sounds very simple, but I noticed this happens when I take a test shot with my tripod looking through the viewfinder and then I step away and use a remote switch and the exposures are always different.
Rich
Good thought, but no. You're correct in that it's a good idea to cover the eyepiece when shooting in 'normal mode' on a tripod, due to light entering the VF and affecting the metering. That's why Canon provides the little rubber eyepiece cover (on the strap), although personally I just hang the lens cap over the eyepiece since that saves me having to remove (and lose?) the eyecup.
But, in Live View mode the mirror is flipped up, blocking light entering through the VF.
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Yep. That's one reason I'm glad I almost always manually select an AF point (even though the 7D offers an in-between option - Zone AF - where you select a smaller cluster of AF points, I still prefer to choose one myself).
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Hi Richard, I guess your reply was addressed to me, so: I always use the viewfinder cover when shooting with a tripod (normal or live view), nevertheless, sometimes the shots are underexposed (or overexposed) with live view depending on the lighting conditions. As neuroanatomist states, it's not a systematic error but kind of a random one (unless one could be able to figure out the live view exposure calculation algorithm and know ahead if the shot will be underexposed or overexposed).
Updated: neuro makes a good point about the mirror being flipped when live view is active: no light from the viewfinder should reach the sensor as the mirror blocks it.
OK Guys, Thanks for the clarification about the mirror being up in Live Mode.
Rich
Neuroanatomist, when you say "mirror is flipped up", is it as same as mirror lock up?, the reason I 'm asking is that your post actually reminds me of something about [url="http://www.juzaphoto.com/eng/articles/live_view_mirror_lock_up.htm]live view and mirror lock up from Juza's web site[/url], here is what it says
<span style="color: #6daa37;"]"Different types of
Live View and MLU
Nearly all cameras have Live View, but
there are four main different types of Live
View.
A) The most advanced Live View
implementations (currently found in the
Canon 7D and 5DII) allow to shoot
using the electronic first curtain; in other
words, when you press the shutter the camera
reset electronically the sensor to begin the
exposure, then it closes the physical
shutter curtain to end the exposure. With
this kind of live view, you no longer need
MLU.
B) Another implementation of
live view is found into older Canon cameras
(1DIII, 1DsIII). These cameras don't have
the electronic first curtain; when you press
the shutter the camera closes the physical
curtain to reset the sensor, it opens the
curtain to begin the exposure and it closes
again the curtain the end the exposure. With
this kind of live view, you still need MLU."
I'm not a tech guy, I don't even 100% understand what the above is saying, I got really confused. my question is that for rebel XSi, when use live view mode, is the mirror locked up or it's just flipped up but not locked? and how it effects the exposure? thanks.
Yes, when the mirror is up for Live View, that's equivalent to mirror lock up. In fact, since mirror lock up is somewhat buried in the menu options, in situations where you'd want MLU it's often easier to simply activate Live View. So yes, on the XSi in Live View mode, the mirror is locked up and will stay locked up until the end of the exposure, unless you're using 'Quick AF' or you're using a flash with E-TTL (see below).
To counter Juza's misinformation, curtain = shutter. Curtain ≠ mirror. Witholder implementations of Live View that Juza mentions (in cameras without an electronic first curtain), the camera has to close the shutter to start the exposure. In that case, MLU is still not needed, since the mirror is already up. It's likely Juza is confusing the issue by thinking of the autofocus modes in Live View - in 'Quick AF', the mirror is flipped down to use the camera's AF system for focusing. The metering is still performed using the image sensor rather than the dedicated AE sensor. In 'Live AF' (aka contrast-detect AF), the mirror is never flipped down at all, meaning MLU is not needed then, either. On Nikon cameras, apparently, the mirror always flips down then up during Live View shooting - that would make that mode rather handicapped, IMO, since there'd be no way to use Live View and avoid the shake from mirror-slap that can affect exposures of certain lengths (which is the purpose of MLU).
It's also worth noting that even on the 7D, the electronic first curtain (EFC) is not used by default. In Live View, that feature is only usedwith one of the silent shooting modes. Otherwise, the first curtain is mechanical just like on models lacking an EFC. Unlike the 1DIII and 1DsIII that Juza mentions, which don't have EFC, on the XSi in Live View mode, an EFC is used (and is the only option). With the Rebel series, the mirror will cycle after the exposure, since a single motor drives both the mirror and the shutter, so the mirror must cycle to reset the shutter curtains (the 50D/7D/5DII and 1-series bodies have separate motors for mirror and shutter).
There is one situation in which the mirror is flipped down for exposure in Live View, in all Canon cameras offering Live View - that's when you're using an external flash with E-TTL (I or II) metering enabled. For E-TTL metering, a pre-flash detectedthrough-the-lens (thus, TTL)is used to determine the proper flash exposure, and the dedicated AE sensor is needed to measure that pre-flash. But even in that case, for Live View shooting the image exposure determination is still made by the CMOS imaging sensor, not the AE sensor (the AE sensor is used only for determining flash exposure, in that case). Page 26 of the 1DIII White Paper has a nice flow chart showing the specific steps, including when the mirror goes up, and which sensors are used when, for normal vs. Live View shooting with and without flash. Note that on that chart, mirror lockup just means the mirror going up, not the MLU custom function (but, since all MLU does is result in a longer interval between the mirror going up and the exposure being taken, with Live View it amounts to the same thing).
Sorry...that was probably far more than you wanted to read!
Many of Juza's facts are inaccurate. For example, in his review of the 85L and 85/1.8 lenses, he originally stated that the 85L was weather-sealed, and he also stated that it has micro-USM which is false (it uses a focus-by-wire system as opposed to mechanical coupling to actuate the ring-USM motor). At least he reads the comments on his reviews, so he edited the review to state that he 'originally thought it had micro-USM' - but he doesn't admit that he originally wrote it had micro-USM, and the correction to no weather-sealing in the specs table was a stealth edit. In fact, in his review of the 135L, he still states, "The built quality is excellent and, unlike the 85mm f/1.2 that I reviewed few weeks ago, it had the true ring type AF motor..."
Juza takes nice pictures. But I look to him for technical information like I look to Greece for fine wine or the Pacific Northwest for historic architecture...that is to say, not at all.
--John
John, thank you very much for taking the time to answer my question, really appreciate it.
like I said, I'm not a tech guy, it will take me long time to digest it. the bottom line is that as long as I know I don't need to go to menu to set MLU when shoot with live view on XSi(I'v been missing my stolen XSi and thinking buy it back since the price is getting cheaper).
...
I don't drink(I drink water only), but I can understand what you mean, I'm pretty sure you have a great taste of it.[]
thanks again!
Hey neuro, look what I got from verifying that!
[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.45.65/IMG_5F00_5075.JPG[/img]
[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.45.65/IMG_5F00_5076.JPG[/img]
[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.45.65/IMG_5F00_5077.JPG[/img]
[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.45.65/IMG_5F00_5078.JPG[/img]
I was stupid enough to take the lens apart and activate live view in my not-so-clean bedroom, and I ended with that big speck. Thankfully, Canon's sensor cleaning function worked this time! (after three tries, actually). As a side note, I know my sensor is not precisely "clean", but I don't think it's worth fully-cleaning it yet (I've had bad experiences with air blowers, so I use the "wet" method: E2 and sensor swabs)
BTW, you're right neuro!, Canon XSi uses an EFC (bad way to figure it out, though).
Hey neuro, look what I got from verifying that!
BTW, you're right neuro!, Canon XSi uses an EFC (bad way to figure it out, though).
Might have been easier to Google "xsi electronic first curtain"... [8-|]
The second link that comes up is this one, and if you scroll down past the images and commentary, you'll find a pasted email from Chuck Westfall (Canon's technical guru extraordinaire, although that's not his official title) which provides confirmation, along with all the juicy details...and the statement that EFC on Rebels is an undocumented feature.
But, there's nothing like confirming something for yourself...kudos to you!
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