It's NOT pellix mirror.
Why people even come with this ridiculous idea. It was known that Sony translucent cameras won't use pellix mirrors even before the A55 release.
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Cons to Translucent mirror?
- Thread starter Naveed Akhtar
- Start date
Why people even come with this ridiculous idea. It was known that Sony translucent cameras won't use pellix mirrors even before the A55 release.
Frenske
Senior Member
Personally I would not worry too much about losing 30% of the light. This equates to log(1-0.3)/log(0.5) = 0.515 =~ 0.5EV. I would be more worried about the small percentages of the 70% of the transmitted through the first mirror interface and reflected at the second one resulting in ghosting.
Naveed Akhtar
Well-known member
So to sum all up:
Translucent mirror will:
Thanks for all your very sensible replies.
Translucent mirror will:
- give ghosting effect
- loss of light (most important for me)
- difficult to clean and maintain (specially if you like to change lenses occassionally)
Thanks for all your very sensible replies.
OK, the analogy breaks down there ... it would be nice if there was an option to turn off the automatic exposure compensation and let the user do it manually.
So your base ISO is 140 instead of 100. I have to believe it's still going to be excellent. But if it's a concern you might want to wait for sample images to download. The A560/580 might be better choices.
- Dennis
Gallery at http://kingofthebeasts.smugmug.com
Glenn
Veteran Member
um Nikon Clips black and is just as dificult to clean.... choose your poison I guess. I don;t thik anyone id going to look for defects in Nikons pictures at 200-500 % so thats dificult to say what defects you'll find there
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The only way I would consider purchasing a camera of this sort would be if the mirror was user-replaceable.
any problem on the mirror will affect ALL pictures.
There's that chance of cleaning going wrong causing damage. I would feel better if the mirror was easy to replace...even on the field.
any problem on the mirror will affect ALL pictures.
There's that chance of cleaning going wrong causing damage. I would feel better if the mirror was easy to replace...even on the field.
Oh, good then. I got that ridiculous idea from Luminous Landscapes and DPR, which both labelled it as a pellicle mirror; do you have a better source the states that it definitely isn't? And if it isn't, what kind of mirror is it?
Pellicle is a thin membrane. In optics it's a semi-silvered thin membrane used to split light. The commercial example is teh Canon pellix which was made of a mylar. The thinness is important to prevent ghosting from internal reflections.
Supposedly the Sony translucent mirror is thin (but thicker) glass and so should not be as susceptibel to mechanical damage of the membrane itself. However, it still remains that it is a thin glass in the optical path. I haven't seen anything definite if it is front or back silvered which would have an impact on the durability of the coating.
I'm not keen on the idea of something in the light path that the manufacturer says not to mechanically clean. I also remember all the posts from SLR newbies who didn't like the dust on the image in the finder and cleaned the focusing screen or the mirror screwing them both up. But at least in that case none of the bad stuff gets in the optical path of the image.
I have no problem waiting until the cameras have been in use for a few years, Pete Ganzel takes one apart and describes the construction, and a few of the brave souls who don't believe the manufacturer wash off their mirror and show that everything is beautiful.
I do find it interesting how in less than one year we have gone from everything must support maximum image quality to dirt on the mirror won't have a big effect. (based on their many years of experience with the product??)
tom
Naveed Akhtar
Well-known member
That makes sense, and was my point. The switch should let you switch the sensitivity to default and not the compensated value. If its off you can compensate with the slower shutter spead.
So choice can be selected as "Light loss compensation: a) Slower shutter b) higher sensitivity...
From the sample images of A560 and A33 ... the difference is visible. A55 is not as problomatic as A33 on higher sensitivity. Looks A33 is still using the previous generation sensor in new bodies. Looks if Sony wants to clear the previous stock
Cheers
I don't see why it would have a hidden automatic ISO increase. It reduces the light to the main sensor by 1/2 stop. The main sensor is used for exposure metering. It sees 1/2 stop less; it will set shutter and/or aperture based on the set ISO and the light it measures. The only time this would be a problem is if you are using an external meter. Then you would have to compensate for the fact that the external meter sees 1/2 stop more light than the camera meter. The analogy to a weak neutral density filter is correct.
tom
tom
Actually, the ISO is based on what the sensor sees. If you point two cameras and a light meter and the same scene, all three of them should say (for instance) 1/125s at f/8 and ISO 100. It would be problematic if the SLTs underexposed in that situation. (Not that many SLT users will use an external meter or work with studio lights for shoot in M mode using "sunny f/16" but it would be an ugly exception if those methods didn't work).
So the cameras will ensure that when you set ISO 100, you're getting the right exposure, which amounts to an undercover increase.
- Dennis
Gallery at http://kingofthebeasts.smugmug.com
Dennis that's interesting; I hadn't looked at it that way. Is that documented any place. The reason I ask is because the Canon pellix cameras had a series of notes in their manuals that explained that when using external meters or manual flash that the user would have to compensate for the difference. So on those cameras the in-camera meter was calibrated to compensate (it was in the prism housing like other SLRs), but it obviously couldn't raise the ISO of the film.
tom
I see this 1/2 stop figure thrown around but the SLT designers in their interview have said that the amount of light loss is confidential info Sony will not release - in the end what matters to the end user any way is how the camera behaves.
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A pellicle mirror has advantages optically as it does not suffer from dispersion or ghosting; however, as you say, it is very fragile. In this case Sony appears to have chosen a more robust thin-plate beam-splitter, which does cause a slight visible ghosting under some circumstances. It would be interesting to know if the beam-splitter also causes dispersion (i.e. chromatic aberration) and whether Sony does any software correction of this in the camera.
Presumably any confusion arises because of comparisons with the Canon Pellix.
S.
tbcass
Forum Pro
The loss is about 1/2 stop which isn't a lot. Whether the small increase in noise because of the iso increase needed to compensate, generally visible only at 100%, is a problem worth the advantages the camera has is something only you can decide.
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Tom
Look at the picture, not the pixels
http://www.flickr.com/photos/25301400@N00/
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Tom
Look at the picture, not the pixels
http://www.flickr.com/photos/25301400@N00/
tbcass
Forum Pro
I'm not sure I agree with that. The Pentax has a little more resolution but also a little more noise. It all depends on what you want. I call them essentially equal because they are so close that the difference is unimportant in practical use.
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Tom
Look at the picture, not the pixels
http://www.flickr.com/photos/25301400@N00/
tbcass
Forum Pro
I'm with you but the answer is do not use auto mode. Use P mode and then set the ISO to your desired value. The camera will then use Aperture and shutter speed to compensate for the loss.
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Tom
Look at the picture, not the pixels
http://www.flickr.com/photos/25301400@N00/
Naveed Akhtar
Well-known member
Hi Tom, the ISO undercover increase is obvious if you check the compaison on A33 with A560 on dcresource page, all ISOs specially 1600 and beyond clearly speaking the same story as, both cameras got the same sensor. It is interesting however that A55 is cleaner, must be some sensor advancement.
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