Sony Alpha A99 Field Test Report

Specifically for the discussion of the A-mount DSLR range
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bakubo
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Re: Sony Alpha A99 Field Test Report

Unread post by bakubo »

bakubo wrote:The ins and outs of ISO: What is ISO?

https://www.dpreview.com/articles/96983 ... hat-is-iso

Raw is often talked about as being like a 'digital negative' but as we've seen, unlike the film standard, the digital version of ISO doesn't specify what should happen in your Raw file.

The latest update to the ISO standard makes it explicit that it does not apply to Raw files. Until a tone curve is applied, a Raw file doesn't have a 'middle grey': it's up to the manufacturer to decide which Raw value should be used. Consequently, there isn’t a specific Raw value you can measure or check for correct lightness, so you can't measure the ISO (or ISO accuracy) of a Raw file.

If you’re ever seen graphs plotting ‘Measured ISO’ against ‘Manufacturer ISO,’ then you risk being misled.

If you’re ever seen graphs of ‘Measured ISO’ plotted against ‘Manufacturer ISO,’ then you risk being misled. What they show is how a camera’s ISO settings are delivered, relative to an arbitrary system that assumes Raw files will saturate at a certain exposure. You can often work out how amplification is being applied using these graphs, but they do not show ISO accuracy, since the ISO standard doesn’t define a relationship between exposure and Raw saturation.
Here is part 2.

Ins and outs of ISO: where ISO gets complex

https://www.dpreview.com/articles/54268 ... ts-complex
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bfitzgerald
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Re: Sony Alpha A99 Field Test Report

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I get what the articles are conveying, however there is no real substitute for practical hands on results.
Having compared all the A Mount cameras, I have seen that they all vary when set to the same ISO value. This is done using the same lens, shutter speed, aperture and ISO value. The KM5d is probably the most accurate, followed by the A77. There is more variation than you should expect. Taking this into account I determined the A77II is about half a stop better at high ISO v the A77
The A77 shows more exposure with identical settings than the 77II does

When I tried the Fuji cameras, I used an adapter and again noticed a big variation almost a stop v the SLT cameras. And that's with the SLT mirror sucking up light. So I concluded from this the high ISO performance of the Fuji XTrans is misleading and over stated. It also showed issues with colour de saturation in low light (even with jpeg or other raw software not ACR). Fuji evidently use SOS system, which conveniently means they can lie through their teeth! (to say their actual real world performance is disappointing is an understatement) Hence I quickly abandoned any notions of using Fuji over A mount (there were other reasons I didn't like many of their lenses rendering or long min focus distances)

So what matters to me is actual field results v an in depth analysis of what ISO is or isn't. I get the vibe and what they are saying - what I am interested in is what happens using the cameras. What's better and by how much, is this field relevant to me? That's what counts
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bakubo
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Re: Sony Alpha A99 Field Test Report

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bakubo wrote:
bakubo wrote:
bfitzgerald wrote:I have read them but I disagree makers are overstating their ISO numbers. I picked on Olympus because they are one of the easy ones to spot..and they have a shady corporate past too so much more likely to cheat :lol:
Awhile back I pulled out my A700 and my E-M5 and shot the same subject in the same light using raw. I was curious to see what the meter would do. I set both to ISO 200 and f2.8:

A700: 1/20
E-M5: 1/25

I shot another subject using ISO 200 and f4:

A700: 1/160
E-M5: 1/160

I looked at the resulting photos and they seemed to be the same. DxO says at ISO 200 the A700 is 150 and the E-M5 is 107 and yet the meters resulted in the same exposures. From a practical standpoint it doesn't seem to make any difference what is happening inside the bowels of the camera as long as the exposures for a given light level and ISO are the same among various cameras. I am talking about from a photographer's perspective.

I do get the impression that I am sometimes out of step on this and other forums though since I am more into the photos than all the nitty-gritty details of what is happening inside the cameras. As long as the results look good to me and I get exposures that I expect for a given ISO then I am okay. So, you can compare photos from various cameras set to a particular ISO and know that you are seeing what they do at that ISO.
On dpreview someone asked a similar question so I got curious again and decided to try a different comparison to see what results I would get. Here it is.

I used my Olympus E-M5 and Panasonic G3 with the Panasonic 20mm f1.7 to take a photo. I set both to ISO 400 and f2 and took the same photo using raw.

G3: 1/20
E-M5: 1/25

DxO says at ISO 400 the G3 is 372 and the E-M5 is 214 and yet the meters resulted in almost the same exposures. Both of the photos look to be the same when I open them in LR 4.4.

I suggest that anyone who is curious do the same with your cameras.
A reminder of what I wrote years ago. :)
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bfitzgerald
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Re: Sony Alpha A99 Field Test Report

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I've used neither camera my only experience is with more up to date ones. What happened with ISO back then v now might not tie up at all. I think Fuji and Olympus were singled out as being way off their quoted ISO figures. I've no hands on use of Olympus in recent years, with Fuji it was very obvious the difference quite notable. Not even open to debate with the tests I did myself.

With DxO I'm not entirely convinced on their testing methods so I wouldn't cast things in stone on that site either. I do however trust my eyes
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bakubo
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Re: Sony Alpha A99 Field Test Report

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Yeah, I realized even back then you were trying to ignore my post because it was inconvenient. :)
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bfitzgerald
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Re: Sony Alpha A99 Field Test Report

Unread post by bfitzgerald »

It's not inconvenient, I base my own findings on what I find simple as. If you disagree I don't mind/care. I for one won't try to defend any maker for over inflated high ISO numbers. You can try to technical discussion around it, but it's pretty open and shut. Some makers lie more than others. As an end user I care about practical results, that's it.
I can say 100% Fuji overstate significantly compared to other brands I have used, for Olympus if I use one I'll report back. Based on feedback from others they also are less than accurate. There is no debate from my end at all
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