a57 v d5100 for first DSLR

Started Apr 6, 2013 | Questions thread
peevee1 Veteran Member • Posts: 6,247
Re: a57 v d5100 for first DSLR

Bjorn_L wrote:

123Mike wrote:

Bjorn_L wrote:

123Mike wrote:

That is your hypothesis. I have another: the sensor is more sensitive to begin with.

Amusing theory given that they use the same sensor.  The a57 just gives up 1/3 to 1/2 stop due to their puzzling use a old technology called a Translucent Mirror.  It is possible to have an EVF without this loss (such as Olympus and Panasonic do).  I don't understand what advantage Sony thinks they get with this approach.  The viewfinder in the gh2, for example, compares favorably to the Sony ones I have seen.

End of day, the end results aren't much apart. Much less than you suggest based on your belief that it must be bad because "light is taken away". But it won't matter what anyone says. Beliefs isn't something that anyone can influence.

Again you are just wishing for stuff without checking out the facts. The above makes no more sense than your assertion that the same processer in the a57 and d5100 perform differently. The effect of the translucent mirror is well known. This is not new tech or some murky unknowable magical thing. Beliefs have nothing to do with it, except for your defense of the a57 of course. The cost of this approach is quite well documented.

You should also read a little more carefully. I said what a translucent (or pellicle) mirror does and wondered why Sony uses them since it does not seem to give any benefit that I can see worth that much of the light not hitting the sensor (in comparison to other EVF methods). Canon first used this in 1965. Nikon also used it briefly around 1978. So a well-known and well tested old technology abandoned by everyone else who tried it... presumably due cost not being worth the payoff.


Back on the translucent mirror.... I do not understand the benefit over other mirrorless designs. This is all I said above. It does have a price... loss of some light (around 1/2 stop by most accounts) as well as a trivial reduction in DR, color and image detail. So that is the cost, what is the benefit over, for example, Panasonics approach? The GH series certainly has lighting fast and accurate video focus, etc... And so would seem to have the same benefits without the same cost.

The mirror is there to direct part of the light to the large PDAF sensors. Some mirrorless cameras started to have small (pixel-sized) PDAF sensors on the main sensors recently, but they are not that effective, apparently due to the difference in the size (and obviously the newness of the technology).

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