[marco]

[quote name='Brightcolours' timestamp='1283269656' post='2372']

It does? Strange, I do not remember having said that I had, or even hinted at that.



I know what you are trying to drive at... "one can not have an opinion without having used equipment".

Then ask yourself why you visit a website like photozone.de....

[/quote]



To get informations? I'm waiting for the Voigtlaender lens on NEX review. :-) Sorry, I only wonder why you use so much energy to play around with limited informations and not wait some weeks to get a much broader picture if more user report are coming up. Maybe we need a speculation forum part? For me it is annoying if people repeat the same arguments again and again.

[Brightcolours]

[quote name='Marco' timestamp='1283277248' post='2377']

To get informations? I'm waiting for the Voigtlaender lens on NEX review. :-) Sorry, I only wonder why you use so much energy to play around with limited informations and not wait some weeks to get a much broader picture if more user report are coming up. Maybe we need a speculation forum part? For me it is annoying if people repeat the same arguments again and again.

[/quote]

NO speculation, all the information I typed up is already available.

[Guest]

[quote name='Brightcolours' timestamp='1283257693' post='2363']

About the ghosting issue:



Even at very downsized images it still is an issue. I downsized it to 1152x765 pixels, and unless London has every light with a smaller backup light under it, this does illustrate very well the light ghosting problem, akin to ghosts caused by "protective filters".







[/quote]



Is that ghosting for real?



Hmmm... I am very surprised. Is Sony using a pellicle or thin mirror? If it's a thin mirror, it should be an easy problem to solve 'cos one of the faces can be anti-reflection coated...



Otherwise, this is a pretty serious problem. I did not realize it exists on the A55 till now. Does that happen only under certain lighting conditions?

[Brightcolours]

[quote name='thw' timestamp='1283337112' post='2402']

Is that ghosting for real?



Hmmm... I am very surprised. Is Sony using a pellicle or thin mirror? If it's a thin mirror, it should be an easy problem to solve 'cos one of the faces can be anti-reflection coated...



Otherwise, this is a pretty serious problem. I did not realize it exists on the A55 till now. Does that happen only under certain lighting conditions?

[/quote]

Well, it is not all that easily fixed on a mirror (they use a mirror). I am sure it is coated already (has to be, else the problem would be much bigger).



You will see it when there will be strong "lights" in otherwise darker conditions, so usually from dusk till dawn photography. Similar to when "protective filters" start to be a real problem, no matter how expensive and well coated they are. The difference is that with the Sony mirror the reflection only happens in the mirror, with filters you see the bright image reflected back from the sensor and then back again by the filter.



Some examples caused by filters (with filters the ghost lights will appear mirrored through the optical axis):

Uncoated filter (Tiffen):



Multicoated filter (Hoya HMC):





Taken from http://www.pentaxforums.com/forums/pentax-camera-field-accessories/36555-lens-filters-versus-flare-ghost-images.html



Taken from http://dptnt.com/2008/10/uv-filter-or-no-uv-filter/







Basically, do not use protective filters for after dusk exposures. A bit hard to not use the mirror in the A55 though.

[Yakim]

[quote name='Brightcolours' timestamp='1283338697' post='2403']

Basically, do not use protective filters for after dusk exposures. A bit hard to not use the mirror in the A55 though.[/quote]



Indeed. And I so wanted to like this camera. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='' />

[Klaus]

[quote name='Yakim' timestamp='1283348921' post='2409']

Indeed. And I so wanted to like this camera. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='' />

[/quote]



Sorry but there're so many air-glass transitions involved - the mirror is the least of your problems here.

It was no problem on the EOS RT for sure.



I will get one.

[Brightcolours]

[quote name='Klaus' timestamp='1283351452' post='2410']

Sorry but there're so many air-glass transitions involved - the mirror is the least of your problems here.

It was no problem on the EOS RT for sure.



I will get one.

[/quote]

The mirror is the only one that can cause such ghost images, though. The other air-glass transitions get handled pretty well nowadays, in most lenses.



Of course, if one does not care about the low light ghost lights, no reason not to consider the A55.



But the mirror of the EOS RT and EOS-1N RS is not the same as the mirror in the Sony A33/55. So saying that it is not caused by the mirror, because the EOS RT did not show this, is at least a bit questionable.

The pellicle mirror of the EOS RT/1N RS is an ultra-thin mirror that virtually eliminates the reflections. Downside to the ultra thin design was that they were quite fragile.



My hunch is that Sony is using a thicker mirror, which does not avoid the reflections of the beam splitter as successfully. One could probably calculate the mirror thickness from the ghost light images.

[Yakim]

[quote name='Klaus' timestamp='1283351452' post='2410']

Sorry but there're so many air-glass transitions involved - the mirror is the least of your problems here.

It was no problem on the EOS RT for sure.



I will get one.

[/quote]



Are you saying it's the lens?

[Klaus]

[quote name='Brightcolours' timestamp='1283352595' post='2412']

The mirror is the only one that can cause such ghost images, though. The other air-glass transitions get handled pretty well nowadays, in most lenses.



Of course, if one does not care about the low light ghost lights, no reason not to consider the A55.



But the mirror of the EOS RT and EOS-1N RS is not the same as the mirror in the Sony A33/55. So saying that it is not caused by the mirror, because the EOS RT did not show this, is at least a bit questionable.

The pellicle mirror of the EOS RT/1N RS is an ultra-thin mirror that virtually eliminates the reflections. Downside to the ultra thin design was that they were quite fragile.



My hunch is that Sony is using a thicker mirror, which does not avoid the reflections of the beam splitter as successfully. One could probably calculate the mirror thickness from the ghost light images.

[/quote]



Light reflected from the sensor will ultimately hit the "mirror" again. The mirror has an angle of 45 degrees or whatever. So what happens ?

[Brightcolours]

[quote name='Klaus' timestamp='1283433007' post='2420']

Light reflected from the sensor will ultimately hit the "mirror" again. The mirror has an angle of 45 degrees or whatever. So what happens ?

[/quote]

We are not talking about light reflected from the sensor, here, though.



We are talking about light entering the mirror glass at surface one. It travels through the glass, towards surface two, where most will exit it again. Part of the light, however, will reflect off surface two, upwards at 90 degrees (think of your prism experiments in science class in high school).

That light will travel through the glass till it will meet surface one again, at a 45 degree angle. There, part of the light will reflect back at an angle of 90 degrees, towards surface 2 again. And most will proceed there towards the sensor to be registered.



Since the mirror is reflecting up, the ghost image will appear down the "real" image on the photo (images get projected mirrored through the optical axis in cameras).



The reason you never noticed this with for instance an EOS RT probably has to do with the thickness of the pellicle. The RT (and 1N RS) used a very thin membrane that was actually quite delicate (and often would break just from cleaning).

It appears Sony used a much thicker mirror.



What happens with light that gets reflected back from the sensor, I do not know. I guess one thing we can be sure about is that ghost lights caused by UV "protective filters" in night photography will be less intense than on other cameras, because the light will lose 1 whole f-stop by passing through the mirror twice more, again.