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Author Topic: Mirror Lock-up is a bigger deal than previously thought  (Read 10313 times)
Rob C
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« Reply #20 on: April 20, 2009, 02:53:49 PM »
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Quote from: KenS
Why would the edges of the frame suffer from vibration induced blur more than the center?
Was one side of the frame more blurry than the other?
The camera is a rigid body and all parts of the frame are exposed equally.



Q. Why would the edges of the frame suffer from vibration induced blur more than the centre?

A. In the case of the Pentax, and my work with it, the reason seems, to me at least, to be something to do with the manner in which the two curtains open up and close when making the slit that crosses the film plane. I guess that the initial jarr at the start of the opening of the two blinds is high enough to cause a slight movement in the body and that dies down to negligible levels and then hits again with a bang as the travel is completed.


Q. Was one side of the frame more blurry than the other?

A. Where I noticed the effect to be worse was in a series of landscape shots of a harbour where the masts at the extreme right of the transparency were really badly out of focus. I was shooting with slow speeds and small apertures. I am no longer sure which side of the camera the Pentax blinds started their travel, but if from left to right, and you consider the film to be upside down, it would perhaps indicate that the effect was worse at the start of the exposure than the end of it.


The camera is a rigid body and all parts of the frame are exposed equally.

I agree that it´s a rigid body, the reason I bought the damn thing because the alternative, a Mamiya RB or RZ would be like a sail down at a harbour.  (It matters because I live on an island.) Having already lost my shirt on a Bronica 6x7 also bought because I thought it rigid, prevented me being bitten by that same dog twice.

As for the exposure being equal, that´s what they all strive for but do not always manage in real life. In fact, there´s a school of thought that says that it was only with the electronically controlled shutter in the F3 that even Nikon managed that fine trick of perfect exposure across the frame.

Difficult on 36x24mm, probably impossible over 6x7!

Cheers

Rob C
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Ray
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« Reply #21 on: April 20, 2009, 05:57:54 PM »
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Quote from: JeffKohn
I don't see this as much of an issue for single exposures. You flip the mirror up in anticipation of the shot. I'm not suggesting MLU be used for action photography or BIF's, but for landscapes where you care about the getting the sharpest results possible (often at slowish shutter speeds), MLU becomes important.

With a completely static, unchanging landscape, then using MLU for a single exposure whatever the shutter speed, whether the shot needs MLU or not, is probably no disadvantage (outside of a totally unexpected, sudden change of conditions). However, the characteristics of scenes in general can vary enormously from the two extremes of 'action' photography where MLU is totally inappropriate, to the 'static landscape' where one might always use MLU as a matter of course. I'd prefer in general to be able to see what I'm shooting at the precise moment I press the shutter.

The main disadvantage of using MLU would be when auto-bracketing exposures for merging to HDR. If the longest exposure falls within that danger zone where mirror slap is likely to degrade the result, say 1/60th second or slower, then there'd be circumstances when I'd prefer to increase ISO rather than use MLU. As Peter McLennan mentioned, even movement of clouds can be a problem when merging to HDR.
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Nick Rains
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« Reply #22 on: April 20, 2009, 08:42:49 PM »
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Quote from: Ray
The main disadvantage of using MLU would be when auto-bracketing exposures for merging to HDR. If the longest exposure falls within that danger zone where mirror slap is likely to degrade the result, say 1/60th second or slower, then there'd be circumstances when I'd prefer to increase ISO rather than use MLU. As Peter McLennan mentioned, even movement of clouds can be a problem when merging to HDR.

Ray, if using the Canon 5D2 (and some others), when you use Live View, 2 sec self timer and Autobracket all together, the camera makes all three exposures in succession without moving the mirror down between shots. It is about a fast as you could possibly make the shots by hand - but no danger of a slight finger pressure movement. I use it a lot and it works a treat.
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Nick Rains
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Marlyn
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« Reply #23 on: April 21, 2009, 12:35:55 AM »
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Quote from: Ray
Consider also the cumbersome procedure of autobracketing exposure with MLU enabled. It could take up to 10 seconds to take 3 shots even with fairly fast exposures. A lot can happen in 10 seconds.


Using a 1DsIII I use MLU constantly when braketing, and when doing Pano's.    I always select the option "Mirror Lockup, down with Set"

My Settings
- 2 Second timer
- MLU, Down with Set
- 3 (or 5) shot bracket  +/- 1 1/3 generally

When i press the shutter the first time, the Mirror flips up, waits 2 seconds, then takes 3 Shots rapidly (as fast as the High speed auto-fire will take them).  - The mirror STAYS up.
- Move the Head to the next position in the sequence for the pano, press again.    Waits 2 seconds, Shoots the brakets,   rinse, repeat.

Afterwards, either press 'Set' to lower the mirror, or it will do it itself in 30 seconds.


Regards

Mark Farnan
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Ray
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« Reply #24 on: April 21, 2009, 06:33:31 AM »
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Quote from: Nick Rains
Ray, if using the Canon 5D2 (and some others), when you use Live View, 2 sec self timer and Autobracket all together, the camera makes all three exposures in succession without moving the mirror down between shots. It is about a fast as you could possibly make the shots by hand - but no danger of a slight finger pressure movement. I use it a lot and it works a treat.

Nick, I've used the 50D in Live View mode with autobracketing and continuous shooting enabled, and it behaves just like your description of the 5D2. I prefer to use a cable release rather than self timer because I like precise control of the moment, even if it's not always necessary.

However, it seems from JeffKohn's comment that Nikon cameras with Live View do not have this advantage. In Live View mode, the mirror flips down then back up again before the exposure takes place. That seems crazy. Who said Nikon cameras were designed with photographers in mind?  
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Ray
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« Reply #25 on: April 21, 2009, 06:40:59 AM »
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Quote from: Marlyn
Using a 1DsIII I use MLU constantly when braketing, and when doing Pano's.    I always select the option "Mirror Lockup, down with Set"

My Settings
- 2 Second timer
- MLU, Down with Set
- 3 (or 5) shot bracket  +/- 1 1/3 generally

When i press the shutter the first time, the Mirror flips up, waits 2 seconds, then takes 3 Shots rapidly (as fast as the High speed auto-fire will take them).  - The mirror STAYS up.

That's very sensible of Canon to provide such a feature. However, I think this is probably only a feature of the professional series. I've never seen such an option on any of my Canon DSLRs. On the other hand, I'm pretty slack reading instruction manuals   .
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Dick Roadnight
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« Reply #26 on: April 21, 2009, 08:31:45 AM »
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50 Megapixel sensors are not cheap, and if I do not use a tripod (Gitzo Carbon or 10Kg Manfrotto, with geared head) and remote wire release (or flash), the pictures are soft: if you pay three times the price of a D3X, you want better pictures. Even the DSLR has lens (leaf) shutters.

For serious landscapes I will be using a serious mirror-free camera, with leaf shutters and movements: presumably leaf shutters produce less vibration than focal plane?

With higher res and heaver mirrors, you would think that MFDSLRs are much more susceptible to mirror shake.

They used to test cameras and tell you the line pairs per millimetre of the system, but (until now) the quality of digital cameras has been such that "they" have chosen to keep quiet about actual whole system performance.

Of course the Sinar Liquid Crystal shutter is, presumably, vibration-free.

You can watch the subject without looking through the view finder - you can look over the camera, stand where you want the model to look or use the camera remotely, with or without a tethered computer... I don't think they do wire frame view finders for digital cameras, but you do get an optical view finder with the (mirror free, rapid-scan) Seitz 617 digital.
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Hasselblad H4, Sinar P3 monorail view camera, Schneider Apo-digitar lenses
BernardLanguillier
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« Reply #27 on: April 21, 2009, 07:55:38 PM »
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Quote from: JeffKohn
I can understand how you might feel that way shooting Canon. In Nikon-land, live-view is no substitute for MLU, because with live-view the camera still drops the mirror down before taking the exposure and then operates as normal.

Indeed, a major issue with Nikon's impementation of Life view.

But either way, Canon does implement MLU as an implicit part of the Live view process and this does confirm the need and value.

Cheers,
Bernard
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BernardLanguillier
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« Reply #28 on: April 21, 2009, 08:42:04 PM »
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This interesting thread shows that a high resolution sensor makes little sense without a shutter designed to stick to vibrations levels low enough not to affect image quality...

More than ever, the weakest link in the chain is going to define the achievable image quality.

I used to see a clear drop of image quality at low temperatures with my Mamiya ZD and 300 f4.5 combo. Careful analysis showed that the culprit was probably the differential dilatation of the lens mount vs body mount... the colder the temperature, the more play there was between lens and body... to the extend that shutter induced vibration did affect negatively sharpness (I was of course always using MLU).

The day I noticed this was the day I understood that MF manufacturers did probably not have the resources it takes to validate fully complex digital systems.

Either way, larger sensor are more prones to these issues and it clearly shows to me that leaf shutters - either in MF lenses or in Digitars - are the only credible option for MF. Too bad for Mamiya...

Cheers,
Bernard
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Ray
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« Reply #29 on: April 22, 2009, 09:00:15 AM »
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Quote from: BernardLanguillier
This interesting thread shows that a high resolution sensor makes little sense without a shutter designed to stick to vibrations levels low enough not to affect image quality...

More than ever, the weakest link in the chain is going to define the achievable image quality.

I used to see a clear drop of image quality at low temperatures with my Mamiya ZD and 300 f4.5 combo. Careful analysis showed that the culprit was probably the differential dilatation of the lens mount vs body mount... the colder the temperature, the more play there was between lens and body... to the extend that shutter induced vibration did affect negatively sharpness (I was of course always using MLU).

The day I noticed this was the day I understood that MF manufacturers did probably not have the resources it takes to validate fully complex digital systems.

Either way, larger sensor are more prones to these issues and it clearly shows to me that leaf shutters - either in MF lenses or in Digitars - are the only credible option for MF. Too bad for Mamiya...

Cheers,
Bernard

I've never compared the effects of shuuter vibrations at different shutter speeds. Is this an issue, and if so, where's the evidence? It should be easy to test. Take a number of shots at various shutter speeds with MLU enabled, and see if you can detect any difference between, say, 100th sec and 1000th sec.
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Rob C
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« Reply #30 on: April 22, 2009, 09:36:56 AM »
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Quote from: Ray
I've never compared the effects of shuuter vibrations at different shutter speeds. Is this an issue, and if so, where's the evidence? It should be easy to test. Take a number of shots at various shutter speeds with MLU enabled, and see if you can detect any difference between, say, 100th sec and 1000th sec.



Ray, I think the range you mention is too high, in that it is perhaps able to mask movement by itself, by virtue of speed. From a second to about a 100th would be more useful, I´d have imagined.

I agree with Bernard that focal plane shutters are not a good idea on MF at 6x6 or above, even with film. They were the bug-bear for the early ´blads and even Rollei slrs, not to mention the problems I personally encountered with the Pentax 67. I suppose you have to make the decision about what you intend to do with MF. If you are a tripod-based user, then who needs anything above a 500th; if you do, then perhaps other formats are really more suited to your requirements. Yes, lenses with built-in shutters cost more, but then if you´re buying into that system you can probably afford it.

I remember that even when I was using F Nikons for fashion and other model-based stuff outdoors, that I would have welcomed a small selection of shuttered lenses to allow synched flash at perhaps better than 250th, which already meant dropping quality by going for the FM or FM2 though if memory serves, the later F4 allowed the same synch too... Having said that, even with the synch option available with bult-in shutter lenses, there used to be flash manufacturer warnings not to go over a 250th in case of cutting off some of the flash, slow flash being used to create the higher power rating to sell more units etc. etc.

Rob C
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Luis Argerich
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« Reply #31 on: April 22, 2009, 09:47:10 AM »
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Don't know if this helps but I just tested my Canon 40D, in AEB mode with 2 seconds time if I enter live view the mirror goes up, then press the shutter and the 3 exposures are taken without lowering the mirror. Then the mirror stays up so for HDR panos you can just move the camera and take the next 3 Live view even helping compose the overlapping between shots.

I tried handheld at 1/125 1/500 1/30 and the response was so fast that the images almost register perfectly without alignment. I'm surprised.

Having said that I found this thread very interesting and I'm thankful for the information everybody wrote here. I hope my 2 cents help.

Luigi
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David Sutton
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« Reply #32 on: April 22, 2009, 05:01:56 PM »
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Quote from: Ray
I've never compared the effects of shuuter vibrations at different shutter speeds. Is this an issue, and if so, where's the evidence? It should be easy to test. Take a number of shots at various shutter speeds with MLU enabled, and see if you can detect any difference between, say, 100th sec and 1000th sec.
It probably depends on the camera, tripod and head, but on my 40D with my tripod, shutter vibration is clearly visible at about half a second and is dealt to by putting a bean bag on the camera. I'm guessing, but I think the critical range is about 2 seconds down to about 1/20th.
David
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photolinia
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« Reply #33 on: April 23, 2009, 04:33:14 PM »
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This discussion is very interesting...  I've been thinking about the ideal purpose for MLU.

Here are my thoughts - based more on engineering background than on photo experience...

Please correct me if I'm wrong

I think the MLU option should only really make sense and be used for longer exposures (typically whenever you would use a tripod -
like sub 1/30 sec).  The mechanical camera vibration caused by the Mirror going up and slapping against the camera chasis is very low frequency and if you have shutter speeds of less than 1/125 sec, most of this vibration will occur after the shot has been taken.

This is particularly true of stuio shots done with strobes, where images are exposed for about 1/1000 sec - the duration of the strobe...

Same thing applies to using a cable release - the spead at which you finger presses and moves the body is very slow and would only
be visible on long exposures...

please correct me if I'm wrong.
-ilya
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Plekto
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« Reply #34 on: April 23, 2009, 06:39:52 PM »
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OTOH, this might be enough to mangle a bracketed shot.  I'd always use MLU and if possible an IR remote to do bracketed shots.  

Q: how many cameras allow you to keep the mirror locked and do multiple exposures as well as have an IR/etc remote?
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Guillermo Luijk
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« Reply #35 on: April 23, 2009, 07:21:28 PM »
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With a cheap and light tripod, a remote shutter and setting MLU + 2secs timer in the camera, I _always_ get perfectly aligned indoor shots with my 350D (they match pixel by pixel).

However several people also using remote shutter and MLU on other cameras have reported they get some (minor) misalignment. Can this be just because of the mirror weight?

I have recently purchased a 5D (Mark I), and would love to have perfectly aligned images as well in HDR bracketings. Any reports on what I can expect from bracketing with tripod, remote shutter, and MLU+timer on a 5D?

Regards.

PS: BTW shame on Canon, one of the reasons for not having gone to 5D2 is that is still only does {-2,0,+2} bracketing.
« Last Edit: April 23, 2009, 07:25:12 PM by GLuijk » Logged

bjanes
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« Reply #36 on: April 23, 2009, 08:41:30 PM »
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Quote from: KenS
Why would the edges of the frame suffer from vibration induced blur more than the center?
Was one side of the frame more blurry than the other?
The camera is a rigid body and all parts of the frame are exposed equally.

Camera shake can occur along three axes and can be described as pan, tilt, and roll. Pan and tilt would affect the center as well as the edges, but roll would have a greater effect at the periphery. However, it seems unlikely that significant roll would occur with the camera on a tripod.

Bill
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Ray
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« Reply #37 on: April 24, 2009, 07:27:16 PM »
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Quote from: GLuijk
I have recently purchased a 5D (Mark I), and would love to have perfectly aligned images as well in HDR bracketings. Any reports on what I can expect from bracketing with tripod, remote shutter, and MLU+timer on a 5D?

Guillermo,
You can expect any movement in the scene to spoil the results   .
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Guillermo Luijk
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« Reply #38 on: April 25, 2009, 07:34:15 AM »
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Quote from: Ray
Guillermo,
You can expect any movement in the scene to spoil the results   .
But movement in the scene is not an issue, the moving area just needs to be masked. My worry is about the heavy mirror included in the 5D (compared to the little 350D).
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Ray
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« Reply #39 on: April 25, 2009, 08:46:03 PM »
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Quote from: GLuijk
But movement in the scene is not an issue, the moving area just needs to be masked. My worry is about the heavy mirror included in the 5D (compared to the little 350D).

The heavier mirror of the 5D is probably what contributed (in my experiments) to the noticeable image degradation at 1/30th sec on a fairly lightweight travelling tripod (but firmly planted on a tiled floor) compared to the complete lack of image degradation from my 20D on the same tripod at the same shutter speed without MLU being enabled. But I still think it's reasonable to deduce that the unusually noisy mirror-flip (and possibly also shutter) of the 20D probably helps image quality, in the absence of MLU. The lower frequency vibrations are transformed into harmless higher frequencies, which are not good for wildlife shots of course. There's a trade-off.

Such issues really require a lot of time-consuming experimentation under various conditions. I'm all in favour of 'knowing thy equipment', but most of us would rather spend our time just taking photos. It requires a scientific frame of mind to make such careful comparisons to determine at what shutter speeds on a particular camera, on a particular tripod, MLU has the most benefit, if any benifit at all.
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