igor_s

igor_s

Joined on May 2, 2006

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On What is equivalence and why should I care? article (2016 comments in total)

One thing left uncovered in the article - about the "reach". Many people think that a smaller sensor automatically gives a longer reach with the same lens focal length ("through equivalent focal length"). In reality, there matters not the sensor size but the pixel pitch. Sure, usually the smaller the sensor the smaller the pixels are, but this relation is not straightforward.

Direct link | Posted on Jul 7, 2014 at 16:29 UTC as 319th comment
On What is equivalence and why should I care? article (2016 comments in total)
In reply to:

RFC1925: I would summarise the article regarding the difference between MFT and FF like this:

If you want:
1) Shallow DOF = FF is better
2) Deep DOF = MFT and FF are tied (FF can compensate with better ISO performance)
3) Portability = MFT is better

All the above have exceptions of course since there are such a great variety of cameras and lenses in both formats.

2) FF can not always "compensate" because on any format the resolution drops from about F/11 due to diffraction. In comparatively good light you can shoot at F/11 on FF as well as on MFT where the DOF will be deeper.

Direct link | Posted on Jul 7, 2014 at 16:23 UTC
In reply to:

igor_s: Simulation of higher ISOs by brightening in the post decreases the SNR, therefore, the comparison is not fair. However, the 7S has lower level of shadow noise, and therefore should do better at extra high ISOs (where the sensor is poorly illuminated). Perhaps natively by about 1 eV if in "boosted" ISO tests it wins by 2 eV.
Unfortunately the above applies only to ISOs above 51200 (if you ever need it and satisfied by the quality). At lower and moderate ISOs the A7S loses to the a7R even in shadows. A specific ultra-low light camera.

Rishi, to compare the normalized Full SNR curves for the 5DIII and A7S, you may simply rise the first one by 3 dB (24 Mp vs 12 Mp). In that case, it will cross the 400K curve for the 7S near the X axis. So, the a7S does have a 2 stops advantage over the 5DIII, but only where the SNR is close to zero(g).

Direct link | Posted on Jun 25, 2014 at 17:40 UTC
In reply to:

mosc: A lot of comments read like: Yes A7S makes sense at 6400+ ISO but who shoots that? The other cameras beat it soundly at base ISO.

But similarly, who needs all the detail of a FF camera at base ISO? You put it on a monitor, even a 4k monitor, that's a lot of crop. You print it out, that's a lot of wall space. The A7S is fractionally less wall space and fractionally less cropping. That's not much of a sacrifice for the added sensitivity. If I have all the light in the world and reach for an A7S instead of an A7R, how much practical difference does it make? I say little to none. In bad light, it makes a big difference. You guys have it backwards.

Not simply at ISO above 6400 but ONLY in shadows. A device for detecting a black cat in a dark room.

Direct link | Posted on Jun 24, 2014 at 17:13 UTC
In reply to:

igor_s: Simulation of higher ISOs by brightening in the post decreases the SNR, therefore, the comparison is not fair. However, the 7S has lower level of shadow noise, and therefore should do better at extra high ISOs (where the sensor is poorly illuminated). Perhaps natively by about 1 eV if in "boosted" ISO tests it wins by 2 eV.
Unfortunately the above applies only to ISOs above 51200 (if you ever need it and satisfied by the quality). At lower and moderate ISOs the A7S loses to the a7R even in shadows. A specific ultra-low light camera.

@Rishi, thank you for the pointing out the specific behaviour of Canon DSLRs. As to the DxOMark data, either I misunderstand something or the data is presented incorrectly. For the 5DIII on the SNR 18% graph at ISO 100K SNR=15.2 dB. However, on the Full SNR graph for ISO 100K at 18.166% gray SNR=10.8 dB only, which makes about 1.5 stops difference. Which one should we believe/consider?
In any case, I agree that in dark tones the 7S performs considerably better than the competition. But it seems that that is not supported by the similar performance in mid- and bright tones. So, with the A7s you can see more details specifically in deep shadows AND at very highest ISOs. Is it enough to speak loudly about the advantage of the 7S? (I mean in general, not your article).

Direct link | Posted on Jun 24, 2014 at 16:26 UTC
In reply to:

igor_s: Simulation of higher ISOs by brightening in the post decreases the SNR, therefore, the comparison is not fair. However, the 7S has lower level of shadow noise, and therefore should do better at extra high ISOs (where the sensor is poorly illuminated). Perhaps natively by about 1 eV if in "boosted" ISO tests it wins by 2 eV.
Unfortunately the above applies only to ISOs above 51200 (if you ever need it and satisfied by the quality). At lower and moderate ISOs the A7S loses to the a7R even in shadows. A specific ultra-low light camera.

Also, you can check the DxOMark data. Up to ISO 25600, the normalized SNR for the 7S and 7R are equal and the lines are parallel. I do not see any particular reason why at ISO 400K there would appear such a huge difference as 2 eV.
With 5DIII, there is less than 1 eV lead by the 7S at ISO 100K.

Direct link | Posted on Jun 23, 2014 at 18:27 UTC
In reply to:

igor_s: Simulation of higher ISOs by brightening in the post decreases the SNR, therefore, the comparison is not fair. However, the 7S has lower level of shadow noise, and therefore should do better at extra high ISOs (where the sensor is poorly illuminated). Perhaps natively by about 1 eV if in "boosted" ISO tests it wins by 2 eV.
Unfortunately the above applies only to ISOs above 51200 (if you ever need it and satisfied by the quality). At lower and moderate ISOs the A7S loses to the a7R even in shadows. A specific ultra-low light camera.

Rishi, I won't go into the theoretical dephths as to why brightening an underexposed image results in a lower SNR compared to increasing the ISO when shooting. You can do a simple experiment yourself. Shoot a normally exposed image, say, at ISO 1600, then an underexposed image at ISO 400, brighten it and compare. I did it with my 600D, and the difference is huge.
As to the digital in-camera boost at high ISO settings that TrojMacReady pointed out, I am not sure. Theoretically, it could cancel my reservations for that ISO range if it is true.

Direct link | Posted on Jun 23, 2014 at 18:09 UTC

Simulation of higher ISOs by brightening in the post decreases the SNR, therefore, the comparison is not fair. However, the 7S has lower level of shadow noise, and therefore should do better at extra high ISOs (where the sensor is poorly illuminated). Perhaps natively by about 1 eV if in "boosted" ISO tests it wins by 2 eV.
Unfortunately the above applies only to ISOs above 51200 (if you ever need it and satisfied by the quality). At lower and moderate ISOs the A7S loses to the a7R even in shadows. A specific ultra-low light camera.

Direct link | Posted on Jun 22, 2014 at 20:38 UTC as 86th comment | 19 replies

So far the discussion has been purely qualitative. We know only that
the field curvature will depend on the lens design, FL and aperture. So, is it possible to create a not-too-expensive family of lenses (including zooms) with roughly constant FC? If that is not feasible and the FC in the family would range, say, from 1 to 9 arbitrary units, how much improvement we would see with the optimized (5 units) sensor compared to the flat one?

Direct link | Posted on Jun 19, 2014 at 17:33 UTC as 45th comment | 1 reply
On Sigma 50mm F1.4 DG HSM | Art Lab Test Review preview (557 comments in total)

Low contrast at f/1.4 (not uncommon, though).

Direct link | Posted on May 28, 2014 at 15:46 UTC as 89th comment
On Sony SLT-A77 II First Impressions Review preview (637 comments in total)
In reply to:

igor_s: Is the A77II's IBIS configurable for work with non-chipped lenses of different FL?

What adapter model did you use? I mean, it should be programmable for FL.

Direct link | Posted on May 2, 2014 at 18:12 UTC
On Sony SLT-A77 II First Impressions Review preview (637 comments in total)
In reply to:

igor_s: Is the A77II's IBIS configurable for work with non-chipped lenses of different FL?

In Pentax SLRs you can set the lens FL via the menu. I assume the camera will apply a different amount of sensor shift depending on your setting. You can play with it to achieve the best results with every lens. In any case that is better than nothing. The A77 will lock at default 50 mm which makes its IBIS almost useless already for a 100 mm lens.

Direct link | Posted on May 1, 2014 at 22:05 UTC
On Sony SLT-A77 II First Impressions Review preview (637 comments in total)

Is the A77II's IBIS configurable for work with non-chipped lenses of different FL?

Direct link | Posted on May 1, 2014 at 20:29 UTC as 67th comment | 5 replies
On Sony SLT-A77 II First Impressions Review preview (637 comments in total)
In reply to:

igor_s: I can not figure out why Sony refuses to add the on-chip PDAF feature to its A-mount models. For now, it seems the only way to make the AF ultimately correct while enough fast (like on the A6000). Now I see again that cr----- AF microadjust which means that the user won't be able to shoot reliably with fast lenses. If one needs 12 fps with tracking he can use the SLT system. But in a different situatuion he may be interested in the ultimate reliability of the AF system. Will see how fast the A77II's conventional CDAF system is.

For me, the only question is, whether the on-chip PDAF would be faster than the CDAF (btw, does the A77II really have at least CDAF?)

If it would, Sony should have added it. I do not care about the SLT in this respect.

Direct link | Posted on May 1, 2014 at 20:26 UTC
On Sony SLT-A77 II First Impressions Review preview (637 comments in total)
In reply to:

igor_s: I can not figure out why Sony refuses to add the on-chip PDAF feature to its A-mount models. For now, it seems the only way to make the AF ultimately correct while enough fast (like on the A6000). Now I see again that cr----- AF microadjust which means that the user won't be able to shoot reliably with fast lenses. If one needs 12 fps with tracking he can use the SLT system. But in a different situatuion he may be interested in the ultimate reliability of the AF system. Will see how fast the A77II's conventional CDAF system is.

Why won't the A-mount lenses work in a mirrorless camera? The Canon 70D has the on-chip PDAF detectors and uses the same EF/EFS lenses adapted for the standalone PDAF detector.

Direct link | Posted on May 1, 2014 at 19:28 UTC
On Sony SLT-A77 II First Impressions Review preview (637 comments in total)

I can not figure out why Sony refuses to add the on-chip PDAF feature to its A-mount models. For now, it seems the only way to make the AF ultimately correct while enough fast (like on the A6000). Now I see again that cr----- AF microadjust which means that the user won't be able to shoot reliably with fast lenses. If one needs 12 fps with tracking he can use the SLT system. But in a different situatuion he may be interested in the ultimate reliability of the AF system. Will see how fast the A77II's conventional CDAF system is.

Direct link | Posted on May 1, 2014 at 18:57 UTC as 77th comment | 7 replies
On Sony a6000 First Impressions Review preview (899 comments in total)
In reply to:

DT200: Big Disappointment.
The VF is worse and sensor will either be the same or slightly worse than the NEX 7 due to all the PDAF pixels (just tlike the NEX 6 was slightly worse).
Even if the the PDAF works this time, there are still no long lenses with wide apertures to use it with. The 55-210 is too slow and is F/6.3.
I guess you could wait for the 70-200mm lens, but its size is bigger than the Canon and Nikon full frame versions which defeats the purpose of the system.
For now the NEX 7 is a bargain. Better VF, possibly better sensor and instead use less expense more abundant legacy lenses.

I think that Sony E 70-200 f/2.8 is much SMALLER than the respective Canikons.

Direct link | Posted on Feb 12, 2014 at 18:59 UTC
On Using third-party lenses on Sony Cyber-shot a7 / a7R article (491 comments in total)
In reply to:

igor_s: Much the same what I thought about this. No sensor-shift IS, poor ergonomics, not-so-good focus aids implementation. An A-mount camera would be much better for IS and handling, but you would not be able to use any Canon, Konica or Minolta lenses with it (at least for infinity).
Anyway, it Sony offered the Z-axis sensor-shift AF, that would be awesome.

That is not my idea, there's been some rumors about that:
http://www.dpreview.com/forums/post/52093143

Direct link | Posted on Jan 23, 2014 at 17:06 UTC
On Using third-party lenses on Sony Cyber-shot a7 / a7R article (491 comments in total)

Nowadays the IS is essential for almost any general-use system. That's it.

Direct link | Posted on Jan 23, 2014 at 00:25 UTC as 55th comment | 3 replies
On Using third-party lenses on Sony Cyber-shot a7 / a7R article (491 comments in total)

Much the same what I thought about this. No sensor-shift IS, poor ergonomics, not-so-good focus aids implementation. An A-mount camera would be much better for IS and handling, but you would not be able to use any Canon, Konica or Minolta lenses with it (at least for infinity).
Anyway, it Sony offered the Z-axis sensor-shift AF, that would be awesome.

Direct link | Posted on Jan 22, 2014 at 22:34 UTC as 57th comment | 2 replies
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