a57 v d5100 for first DSLR

Started Apr 6, 2013 | Questions
Bjorn_L
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Re: a57 v d5100 for first DSLR
In reply to peevee1, Apr 9, 2013

peevee1 wrote:

kangaroo in oz wrote:

Hi guys

Besides the faster frame rate in the a57  i was just wondering if there is much difference in these cameras which would sway you to go one way or the other if you were recommending a DSLR for a first time buyer..

Price seems on par

Cheers 

Video. A57 can AF in video, and you can use viewfinder when shooting video. Also it has 1080p60 option. No contest here.

They use the same sensor, but due to fixed semi-transparent mirror in A57, high ISO is somewhat worse.

But D5100 produces worse colors in JPEG. Use their image comparison to see for yourself:

D5100

A57

I see smearing and loss of detail.  I believe the a57 was just using a higher level of ISO noise reduction.  This is an in camera setting which can be adjusted up on most cameras.

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peevee1
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Re: a57 v d5100 for first DSLR
In reply to peevee1, Apr 9, 2013

Oh, and A57 stabilizes every lens, D5200 only those which have stabilization built-in (that excludes all primes for example).

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peevee1
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Re: a57 v d5100 for first DSLR
In reply to NowHearThis, Apr 9, 2013

EVF gives you 100% view, better than the bad OVF of D5100, and you can shoot into the sun with it. Don't try it with OVF.

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123Mike
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Re: a57 v d5100 for first DSLR
In reply to Bjorn_L, Apr 9, 2013

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.

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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.

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Bjorn_L
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Re: a57 v d5100 for first DSLR
In reply to 123Mike, Apr 9, 2013

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.

You shooting off your mouth without the facts just makes you look silly.

"The a57 has a more sensitive sensor..." no, it has the same sensor

"The loss is not as bad as you believe..." no, it is tested and documented and not a matter of belief.

What next? Name calling, I'm betting. How about we skip that step and you just read up on it. Knowing the facts won't make your camera any more or any less it will just acquaint you with the facts. I'm not saying you chose a bad camera; just pointing out there is a benefit to understanding your cameras advantages and disadvantages.

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.

Of course this is only relevant to this thread in comparing the a57 to the d5100 which does not have these penalties but also does not have the fast video focus. Still think how much more compelling the a57 would be if it used a different EVF implementation.

If you think about it the costs make sense... it puts a semi-transparent object between the lens and the sensor, additionally this object is at an angle. There is no way this cannot have an effect. Light passing through anything is impacted.

A little info about the mirror tech (more links in the article if you want to understand it better)

http://en.wikipedia.org/wiki/Pellicle_mirror

http://thesybersite.com/sony/a55/index.htm#slt_mirror_image_quality

From DXOMark, the defacto industry standard for raw sensor performance.  Used by a great many highly respected review sites (including this one).

Copy the entire mess and paste it in to your browser for a comparison of raw sensor performance.  Keeping in mind that despite your earlier assumption they use the same sensor but the d5100 clearly out performs the a57 at the sensor.  This is not because the a57 is bad or using an inferior version of the sensor.  It is just illustrating the cost of this translucent mirror.

http://www.dxomark.com/index.php/Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/(appareil1)/798%7C0/(brand)/Sony/(appareil2)/698%7C0/(brand2)/Nikon

The above link is probably also of interest to the OP in evaluating these two cameras.

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Wally626
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Re: a57 v d5100 for first DSLR
In reply to Fat Dragon, Apr 9, 2013

Fat Dragon wrote:

Wally626 wrote:

Checked my A77 versus a light meter in a very unscientific test.

Camera multi spot mode says 1/50 at f/2.8 ISO 1600

Camera spot meter mode on small 18 percent grey card centered in the scene says 1/15 at f/2.8 ISO 1600

Incident light meter says between 1/30 and 1/60 at f/2.8 ISO 1600

In the image the one using the camera spot meter was too bright the multi spot and incident meter shots were exposed corectly. Base on rough approximation the meter was probably about 1/40 versus the 1/50 the camera gave so pretty close.

The Sony camera is probably calibrated for a 12 percent gray card which would be why the scene was a bit over exposed using an 18 percent gray card.

To help a layman out, would this test indicate differences in actual ISO levels between various cameras, or simply a different approach to metering in the SLT as compared to an SLR or incident light meter?

To measure the difference in the cameras ISO setting you would need a calibrated test lab. Essentially take a picture of an object with known brightness under well controlled conditions. Using an incident light meter you can measure exactly how much light is illuminating the object of interest. Set the camera to the shutter speed aperture and ISO combination that should provide a well exposed image. If the image is well exposed then the camera ISO is set correctly. I have an incident light meter but it is not a calibrated model and cannot be used to get absolute numbers.

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godfather927
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Re: a57 v d5100 for first DSLR
In reply to kangaroo in oz, Apr 9, 2013

kangaroo in oz wrote:

Hi guys

Besides the faster frame rate in the a57  i was just wondering if there is much difference in these cameras which would sway you to go one way or the other if you were recommending a DSLR for a first time buyer..

Price seems on par

Cheers 

As was already mentioned, if you're using the DSLR for video then i'd suggest the a57 as its features are clearly better suited for that task. It was this reason, along with in-body stabilization for reducing shake even with cheaper prime lenses that swayed me to purchase the a37 over the D3100.

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T Evergreen
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Re: a57 v d5100 for first DSLR
In reply to Wally626, Apr 9, 2013

As a Pentax user, I've got no preference for either brand, but it appears that the Sony has some interesting and useful features (like Pentax) that are not in the Nikon which are beneficial in a first camera.  The Sony has image stabilization built into the camera body, so any lens mounted on the camera will allow slower shutter speeds before shake becomes apparent.  With Nikon, shake reduction is built into the lens, but not all lenses have that feature.  Sony also has it's auto focus motor built into the camera body, so legacy lenses can be auto focused.  For the Sony that means you can use Minolta auto focus lenses dating back to the mid-1980s, according to what I've heard.  With the Nikon, you can only use lenses with focus motors built into the lens itself.  A third feature is focus peaking whereby high-contrast edges are outlined in color to show the area in focus.  The user can select which color (white, red, or yellow) is used for highlighting the in-focus objects, and this can be especially useful with manual focus lenses or in macro photography.

As far as ISO accuracy goes, I believe the DP Review for the A57 says the ISOs are within 1/6 stop at all settings.  And as far as image quality goes, I doubt there is much difference between the two cameras since they both use the same Sony sensor or nearly identical ones.

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Leonard Migliore
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Re: Neither
In reply to Fat Dragon, Apr 9, 2013

Fat Dragon wrote:

Leonard Migliore wrote:

Fat Dragon wrote:

To help a layman out, would this test indicate differences in actual ISO levels between various cameras, or simply a different approach to metering in the SLT as compared to an SLR or incident light meter?

Most recent Sony sensors are "ISOless', meaning that their noise levels do not depend on the selected ISO. So all the test indicates is the level of amplification of the sensor signals to produce a specific brightness level on a JPG. Which is something only of significance to the sensor electronics designer and his priest.

I'm probably missing a lot of knowledge here, but it sounds to me like you're saying that I could shoot my girlfriend's A57 at ISO 6400 with the same noise level as ISO 100. Since my girlfriend is slow to pick up the basics of exposure (she insisted on an SLR but in her heart she wanted a point-and-shoot that doubles as a status symbol), I've got a lot of shots on file that she took at higher-than-necessary ISOs, and my untrained eye suggests that they're a lot noisier than the low-ISO shots we've gotten from the camera.

It's not a free lunch. Shots taken with exposures consistent with high ISO's will be noiser than ones with more exposure. It's just that the ISO dial doesn't do much besides change the exposure.

Let's say you're shooting indoors and need 1/2 second at f/2.8 at ISO 100. You know that's no good for motion blur. You want to shoot at 1/125. The standard way to do this is to bump the ISO to 6400. And this is going to be noisy. But with the Sony, you would get the same noise and better highlights if you kept the ISO at 100 and set your exposure manually to 1/125. Your JPG would be just about black but if you bump up the RAW file, you'll get the same result as increasing the ISO because that's all the camera does.

You'll get more noise with low exposure regardless of the ISO setting. So bumping up brightness 6 stops in an ISO 100 shot will show the same noise as if you took it at ISO 6400.

Or maybe you mean that the ISO is essentially a function of the image processor, in which case more processing (i.e. higher ISO) introduces more noise. I don't think the problem is your ability to communicate the idea, but my ability to understand it, since my camera-speke (Photographese?) is pretty basic.

ISO is a standards organization. They developed a photographic exposure standard for film. It's used for digital sensors but it wasn't created for them and it's probably too late to create a new paradigm.

Noise comes from low exposure, image brightness comes from the degree of amplification of the sensor signal. There isn't much noise in the amplifiers anymore; they're just amplifying the noise that's already in the signal.

I think the manufacturers try to set a base ISO that's consistent with the most exposure the sensor can stand without saturating in the highlights but that's sort of a fuzzy concept so there's going to be differences. But whatever they set it at, they can make the JPG's look right with respect to brightness.

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Leonard Migliore
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It lets the camera focus
In reply to Bjorn_L, Apr 9, 2013

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.

The mirror in the SLT is, obviously, not used to look at the image since the EVF runs off the sensor as it does with all mirrorless cameras. It is, rather, used to allow phase detection autofocus like SLR's have. Phase autofocus is much faster than contrast autofocus, which is used by other mirrorless systems.

So it's a kluge, but it replaces another and more massive kluge, the reflex viewing system. I would expect all this stuff to be gone when on-sensor phase detection becomes more mature.

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headfirst
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Re: a57 v d5100 for first DSLR
In reply to Bjorn_L, Apr 9, 2013

Bjorn_L wrote:This is because the a57 uses some of the incoming light for the viewfinder.  This is not technically neccessary but it is how Sony has chosen to do it.

This is incorrect - the SLT design redirects some of the light for Phase Detect AF, it is not used for light to the viewfinder (that is a fed off the imagin sensor).

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123Mike
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Re: a57 v d5100 for first DSLR
In reply to Bjorn_L, Apr 9, 2013

I understand all that. I thought that there are minor things one can do to the sensor, like choosing voltage levels, who knows. I can accept that there isn't anything one can do to make a sensor magically better. If it's the same sensor, same version of the sensor (is it? noone ever talks about revisions - neither do we get to hear about that from manufacturers - so all we can do is speculate).

Go here: http://www.dpreview.com/reviews/sony-alpha-slt-a57/18

Select ISO 1800, pick the D5100 from the list. Browse around the picture. I'm not seeing much difference at all. I'm seeing green feathers that look better on the A57 version. I'm seeing other parts there look better on the D5100 version. I'm seeing lens issues I think as well.

End of day, does the D5100 evidently show much better results? Not according to that test it doesn't. So, I'm sticking with my -5 to 10% better ballpark.

So, that brings us back to all those features. So how about all those features that the Sony has that the Nikon does not...?

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headfirst
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Re: a57 v d5100 for first DSLR
In reply to Bjorn_L, Apr 9, 2013

Bjorn_L wrote

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 benefit is being able to use dedicated phase detect AF sensors. Even at it's best current Contrast Detect is not as fast or able to track moving targets as well.

Given time & more development Contrast Detect or on-sensor PDAF (or possibly even some other technology) will come upto or even surpass that but it isn't there yet & it certainly wasn't 3 years ago.

I don't think that anybody thinks that SLT is here to stay, it's a stopgap until other solutions appear or improve. At that point we can have cameras with excellent all round AF, no moving mirrors & quite probably by then no moving shutter either.

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Fat Dragon
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Re: Neither
In reply to Leonard Migliore, Apr 10, 2013

Leonard Migliore wrote:

It's not a free lunch. Shots taken with exposures consistent with high ISO's will be noiser than ones with more exposure. It's just that the ISO dial doesn't do much besides change the exposure.

Let's say you're shooting indoors and need 1/2 second at f/2.8 at ISO 100. You know that's no good for motion blur. You want to shoot at 1/125. The standard way to do this is to bump the ISO to 6400. And this is going to be noisy. But with the Sony, you would get the same noise and better highlights if you kept the ISO at 100 and set your exposure manually to 1/125. Your JPG would be just about black but if you bump up the RAW file, you'll get the same result as increasing the ISO because that's all the camera does.

You'll get more noise with low exposure regardless of the ISO setting. So bumping up brightness 6 stops in an ISO 100 shot will show the same noise as if you took it at ISO 6400.

So it's just a software function within the camera. Gotcha. Is that true for all digital cameras or just some?

ISO is a standards organization. They developed a photographic exposure standard for film. It's used for digital sensors but it wasn't created for them and it's probably too late to create a new paradigm.

I'm familiar with the ISO, but I always thought camera ISO was something different. I've heard it called "Initial Shutter Opening" before, which, to a layman like myself, simply sounds like a camera jargon term. Since a Bing search (Google's unreliable here in China) shows 8 results for "Initial Shutter Opening", I'm not really certain where I heard this term. Always good to learn something new like this, especially when it cancels out something I had wrong before.

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peevee1
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Re: a57 v d5100 for first DSLR
In reply to Bjorn_L, Apr 10, 2013

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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peevee1
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Re: Neither
In reply to Fat Dragon, Apr 10, 2013

Fat Dragon wrote:

Leonard Migliore wrote:

It's not a free lunch. Shots taken with exposures consistent with high ISO's will be noiser than ones with more exposure. It's just that the ISO dial doesn't do much besides change the exposure.

Let's say you're shooting indoors and need 1/2 second at f/2.8 at ISO 100. You know that's no good for motion blur. You want to shoot at 1/125. The standard way to do this is to bump the ISO to 6400. And this is going to be noisy. But with the Sony, you would get the same noise and better highlights if you kept the ISO at 100 and set your exposure manually to 1/125. Your JPG would be just about black but if you bump up the RAW file, you'll get the same result as increasing the ISO because that's all the camera does.

You'll get more noise with low exposure regardless of the ISO setting. So bumping up brightness 6 stops in an ISO 100 shot will show the same noise as if you took it at ISO 6400.

So it's just a software function within the camera. Gotcha. Is that true for all digital cameras or just some?

Now, it is BS. Typically, it is a combination of software and hardware, for example, up to ISO 6400 it is real hardware signal amplification, and after that a software multiplier. The difference is that, say, you have a typical level of noise equal to 0 or 1 at ISO 100. Then if you multiply by 16 digitally (ISO1600), all your noise will be 0 or 16, and if you amplify, it will be in the range 0-16, much smoother, with fewer spikes to 16. And part of the noise will not be even multiplied, leading to even lower noise in practice.

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Fat Dragon
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Re: Neither
In reply to peevee1, Apr 10, 2013

peevee1 wrote:

Fat Dragon wrote:

Leonard Migliore wrote:

It's not a free lunch. Shots taken with exposures consistent with high ISO's will be noiser than ones with more exposure. It's just that the ISO dial doesn't do much besides change the exposure.

Let's say you're shooting indoors and need 1/2 second at f/2.8 at ISO 100. You know that's no good for motion blur. You want to shoot at 1/125. The standard way to do this is to bump the ISO to 6400. And this is going to be noisy. But with the Sony, you would get the same noise and better highlights if you kept the ISO at 100 and set your exposure manually to 1/125. Your JPG would be just about black but if you bump up the RAW file, you'll get the same result as increasing the ISO because that's all the camera does.

You'll get more noise with low exposure regardless of the ISO setting. So bumping up brightness 6 stops in an ISO 100 shot will show the same noise as if you took it at ISO 6400.

So it's just a software function within the camera. Gotcha. Is that true for all digital cameras or just some?

Now, it is BS. Typically, it is a combination of software and hardware, for example, up to ISO 6400 it is real hardware signal amplification, and after that a software multiplier. The difference is that, say, you have a typical level of noise equal to 0 or 1 at ISO 100. Then if you multiply by 16 digitally (ISO1600), all your noise will be 0 or 16, and if you amplify, it will be in the range 0-16, much smoother, with fewer spikes to 16. And part of the noise will not be even multiplied, leading to even lower noise in practice.

That clarifies a lot about how ISO works and affects IQ, but I'm trying to figure out exactly what you're calling BS. Do you mean that it's BS (as in disappointing) that Sony uses a system that starts the software multiplier at anything above 100, or that it's BS (as in not true) that Sony's cameras have no hardware ISO amplification? Or maybe something else...

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123Mike
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Re: a57 v d5100 for first DSLR
In reply to peevee1, Apr 10, 2013

Plus it shoots 10 fps in full res, and 12 fps cropped f3.5, and all with full AF.

I think the issue in threads like this though, is that there are certain people that want a particular camera to "win". A Nikon person with Nikon equipment might want to justify their choice. Then no matter what information is presented, it's always downplayed, never acknowledged. It's like a religious war. No amount of evidence will suffice.

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123Mike
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Re: a57 v d5100 for first DSLR
In reply to kangaroo in oz, Apr 10, 2013

It's nice to see the Canons and Nikons no longer being considered the overlord grandmasters of photography. Sony is getting more and more recognized for the many things that they've done that years after the competition still can't do.

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Fat Dragon
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Re: a57 v d5100 for first DSLR
In reply to 123Mike, Apr 10, 2013

123Mike wrote:

Plus it shoots 10 fps in full res, and 12 fps cropped f3.5, and all with full AF.

I think the issue in threads like this though, is that there are certain people that want a particular camera to "win". A Nikon person with Nikon equipment might want to justify their choice. Then no matter what information is presented, it's always downplayed, never acknowledged. It's like a religious war. No amount of evidence will suffice.

Because there is no way to prove which is better. Cats or dogs, Ford or Chevy, Canon or Nikon (or Sony), they all have their upsides and downsides and in the end the "best" answer is the one you choose. Trying to prove someone else's choice wrong rarely gets you anywhere. I'm regularly guilty of trying, but I can't think of a single instance in which I've succeeded.

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