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Author Topic: Mirror slap effect - Contax 645 vs Hasselblad H  (Read 1558 times)
Steve Hendrix
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« on: June 07, 2013, 05:26:07 PM »
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A long overdue test with some interesting results.

https://captureintegration.com/a-look-in-the-mirror-slap-contax-vs-hasselblad-h/


Steve Hendrix
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Steve Hendrix
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BartvanderWolf
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« Reply #1 on: June 07, 2013, 06:32:24 PM »
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A long overdue test with some interesting results.

Hi Steve,

Thanks for the test. Have you also tested at other shutterspeeds?

Cheers,
Bart
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Steve Hendrix
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« Reply #2 on: June 07, 2013, 10:34:25 PM »
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Hi Steve,

Thanks for the test. Have you also tested at other shutterspeeds?

Cheers,
Bart


Hi Bart -

No, just a couple to get a sense of the thing. The amount of time it takes to invest in order to perform a test accurately is substantial. The intent really was to see how much substance existed behind the assumed suppositions and the results were surprising in several ways.


Steve Hendrix
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Steve Hendrix
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EricWHiss
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« Reply #3 on: June 08, 2013, 01:19:06 AM »
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Ah, I was expecting a newer H. but then if you are comparing against the contax, I guess any age is fair.  Amazing how well those have done considering all.   And my goodness, good thing you didn't through the DF into the mix.   Grin
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jerome_m
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« Reply #4 on: June 08, 2013, 01:28:43 AM »
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I am sorry, but I am not sure I understand what the results are. Is the result simply that there is little difference at 1/125s and 2s between the two cameras? Isn't mirror slap more noticeable around 1/15s or 1/30s anyway?
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BartvanderWolf
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« Reply #5 on: June 08, 2013, 06:00:52 AM »
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Isn't mirror slap more noticeable around 1/15s or 1/30s anyway?

Hi Jerome,

That's correct for 35mm DSLRs, it may or may not be similar for the MF platform. That's why I asked if other shutterspeeds were tested as well.

Steve is correct that a good test takes a fair bit of time, but it can be done very accurately with relatively simple means. All it takes is a series of shots at different shutterspeeds of a test target with a horizontal Slanted edge (I have a free one available for download and printing).

That almost horizontal edge will allow to evaluate the (when using the camera in it's landscape orientation) vertical blur, expressed in fractions of a pixel accuracy. One can use a slanted edge evaluation software such as Imatest, or use my free tool when one doesn't mind putting in a bit more effort.

Cheers,
Bart
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Steve Hendrix
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« Reply #6 on: June 08, 2013, 08:03:08 AM »
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Hi Jerome,

That's correct for 35mm DSLRs, it may or may not be similar for the MF platform. That's why I asked if other shutterspeeds were tested as well.

Steve is correct that a good test takes a fair bit of time, but it can be done very accurately with relatively simple means. All it takes is a series of shots at different shutterspeeds of a test target with a horizontal Slanted edge (I have a free one available for download and printing).

That almost horizontal edge will allow to evaluate the (when using the camera in it's landscape orientation) vertical blur, expressed in fractions of a pixel accuracy. One can use a slanted edge evaluation software such as Imatest, or use my free tool when one doesn't mind putting in a bit more effort.

Cheers,
Bart


Yes, and some of those shorter shutter speeds would also take more into account like shutter recoil, etc. So there is some merit there, to get a more complete picture of the camera system as a whole and how it handles vibration. Also instead of just having it on the tripod for objectivity sake, it would be reasonable for someone - moi? - to also do the best at hand holding with each system as well.

At the time we didn't have a slanted edge device, but do now. Maybe when the opportunity arrives, we'll do another - and even include the DF for Eric's sake! I am 100% serious about the time investment. No, it does not take days and days. But to do it right, it does take time and at the expense of something else, returning a phone or an email, supplying someone with some researched information, etc. All of the normal things that come with service and that never ends and always takes priority. This test occurred after (normal) hours when the phones don't ring (as much) and finished up about 11PM.

There is always a sacrifice and also this is just one test. There are countless tests we do and can do, so other tests also are sacrificed. It's not so simple. But - we love doing tests, whether they are perfect or not, we always learn something, even if it is not a complete picture, there is always some knowledge gained.


Steve Hendrix
Capture Integration
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Steve Hendrix
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BartvanderWolf
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« Reply #7 on: June 08, 2013, 09:19:32 AM »
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At the time we didn't have a slanted edge device, but do now. Maybe when the opportunity arrives, we'll do another - and even include the DF for Eric's sake! I am 100% serious about the time investment. No, it does not take days and days. But to do it right, it does take time and at the expense of something else, returning a phone or an email, supplying someone with some researched information, etc. All of the normal things that come with service and that never ends and always takes priority.

Hi Steve,

I agree, and the testing is usually not a goal in itself. However, by adopting a repeatable(!) methodology one can hugely reduce the testing error component, and focus on the phenomenon to be evaluated itself. It also becomes easier to repeat the procedure later, without introducing new variables.

My test target is insensitive to distance variations (as long as shot from more than 25x focal length). So a given lens will always produce the same resolution (on the star blur diameter as well as on the edges), regardless of smallish differences in shooting distance. The star makes it easy to focus accurately, especially with a loupe or when tethered, just aim for the smallest diameter of the central blur area. When shot reasonably square, when the star is in focus, the nearby edges will also be in focus. It also allows to judge a single specimen, amidst others. When a given lens/sensor combination is known to be able and achieve a 98 pixel blur diameter, then any test that produces more blur means that the lens is of lesser quality, or that focusing needs to be done better.

The horizontal slanted edge is used to measure vertical resolution, which is where most of the mirror slap effect is expected to manifest itself. When the target is shot approximately level, the slant will allow to super sample the resolution at 1/10th of a pixel. That's accurate enough to detect even sub-pixel differences.

Since vibrations peter out over time, it will even allow to measure the quality of any vibration dampening effect since we introduce a time-weighted average during the exposure time. If the shake is vigorous, but only lasts a fraction of the effective exposure time, it will be of lesser importance.

It also becomes easier to compare tests performed by others.

Cheers,
Bart
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tsjanik
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« Reply #8 on: June 08, 2013, 11:12:53 AM »
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Hi Steve:

Now that you are a Pentax dealer, you might add the 645D to the mix.  The Pentax 645 series has had a very effective mirror dampening system, e.g. http://www.luminous-landscape.com/reviews/cameras/645-mlu.shtml

Shutter shake can be the real villian and it's not obvious to me how to sort those out if the shutter and the mirror both travel in the same direction, i.e., vertical.

Tom
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jerome_m
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« Reply #9 on: June 08, 2013, 11:19:56 AM »
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The Hasselblad H cameras have a leaf shutter and the mirror can be raised prior to the shot. It will even stay in the up position between shots if one wants (there is a menu for that). That is a very efficient workaround for mirror slap...

Besides, the Hasselblad H camera can also adjust the delay between mirror slap and shutter.
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Steve Hendrix
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« Reply #10 on: June 08, 2013, 12:38:33 PM »
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Hi Steve:

Now that you are a Pentax dealer, you might add the 645D to the mix.  The Pentax 645 series has had a very effective mirror dampening system, e.g. http://www.luminous-landscape.com/reviews/cameras/645-mlu.shtml

Shutter shake can be the real villian and it's not obvious to me how to sort those out if the shutter and the mirror both travel in the same direction, i.e., vertical.

Tom


Yes, perhaps in the future when time allows, we'll incorporate more cameras. Keep in mind the number of tests I'd like to see performed is a very long list and there are some priorities. I think the primary objective here was not to show how numerous cameras differ, but to show how pre-conceptions of the performance between 2 perceived extremes does not always match the reality. But I also feel there is further basis for a test in the future at the other shutter speeds, like 1/30th - 1/8th, which may tell another story.


Steve Hendrix
Capture Integration
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Steve Hendrix
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Steve Hendrix
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« Reply #11 on: June 08, 2013, 12:39:39 PM »
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The Hasselblad H cameras have a leaf shutter and the mirror can be raised prior to the shot. It will even stay in the up position between shots if one wants (there is a menu for that). That is a very efficient workaround for mirror slap...

Besides, the Hasselblad H camera can also adjust the delay between mirror slap and shutter.


Yes indeed, the delay is effective. And the ability to keep the mirror up between shots lends itself well to certain workflows.


Steve Hendrix
Capture Integration
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Steve Hendrix
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MFDB: Phase One/Leaf-Mamiya/Hasselblad/Leica/Sinar
TechCam: Alpa/Cambo/Arca Swiss/Sinar
Direct: 404.543.8475
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