Loss of Contrast in A55 due to Mirror

Started Dec 7, 2010 | Discussions thread
TrojMacReady
Senior MemberPosts: 8,447
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Re: Ha Ha Ha
In reply to Tony Beach, Dec 8, 2010

Tony Beach wrote:

TrojMacReady wrote:

Tony Beach wrote:

TrojMacReady wrote:

Tony Beach wrote:

I took cropped horizontal strips from the fence that went from front focused to back focused from each sample, placed them in a single file lined them up one above the other, then simultaneously selected various portions of the scene and toggled between the layers to see which (if any) file triggered a difference in the contrast. As I said more than once here, regardless of whether the mirror shot was in focus while the other one was not, or vice versa, the non-mirror shot always had slightly more contrast when there was a detectable difference.

I wonder which crops those would be, because the files tell another tale here.

[Snip.]

Because like I said, select the right crops and you can "prove" anything. For example:

[Snip.]

With mirror left, without mirror right, the 135mm F1.8 ZA shots. In this case the one with mirror showing best results.

No they don't. I just checked them and the contrast is the same (even though overall the mirror shot is sharper than the non-mirror shot due to slightly different focus planes).

Check your histogram again.

Here's the histogram from the mirror shot:

and the one without:

Both the numbers and the graphs show the crop from the mirror shot shows more contrast (unsurprisingly, because contrast is partially linked to sharpness too).

Could you post those crops (from both sides of the scene) here for everyone to see?

I've outlined what I did, anyone is free to do it for themselves. I've already wasted too much time arguing about this.

You haven't pointed out which part you selected. It would be fun to show the corresponding histograms here.

Interestingly (to me) was that in the 135/1.8 shot where the plane of focus was very close between the two shots, the out of focus areas both in front and behind the focused part showed less contrast in the mirror shot whereas they were both the same in focused part. I actually have a hypothesis why that would the case, having to do with the scattering of light and how that interacts with the mirror.

See above.

Exposures were consistent with the lighting being consistent. If a cloud rolled over the scene during a shot, the exposure would have changed in a way not accountable by the light differences of the translucent mirror.

There is no "if", we can see the shadows from clouds, in different places.

Sorry, but that is ludicrous. There are no shadows and there the scene is to small an area to be differentially lighted by clouds.

I've already shown the shadows here. So for your own credibility, it's better to just admit they are there.

You can too. Moving shadows doesn't mean metering will automatically result in different physical exposures.

The histograms tell a different story, they show that the scene is consistently lit throughout.

I see inconsistency. A lot of it.

You see some inconsistencies that are there but have no bearing on the contrast, and you see "inconsistencies" that are not there but you imagine make a difference --

The only one imagining differences right now is you. QED

even as you strive to show crops that still show the A55 does better, but nonetheless failed to show more contrast (which was the point of the OP).

I've already posted histograms before in an earlier post, but anyone is free to check for themselves.

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