Another Stupid Camera Test: IQ 260 / A7r / 5d2 / Epic

[Iliah]

If you look at the raw data, IQ260 is exposed 2 stops lower compared to Sony and Canon.

[MrSmith]

Chris you have some really good books in there! Thanks for sharing!

And some dubious DVD's 

[eronald]

If you look at the raw data, IQ260 is exposed 2 stops lower compared to Sony and Canon.

Iliah,

 I'm not sure I understand - the Phase back has a single ISO, right? So if set to 100 it should anyway be underexposed at least 1 stop in raw?

 Could you please post the raw exposure graphs? This might also show us where the "ants" come from ...

Edmund

[Iliah]

Hi Edmund,

Let's select the same black area on both Sony and IQ260 shots, I used the black screen on the chimney:


EV0 on the following histograms is set at the respective sensor saturation points.

Here is the histogram of that area for IQ260, you can see blue is clipped:


Here is the histogram for the same area for Sony A7r:


You can see that the peak on the green channel for Sony is at about -9 EV, while for IQ260 it is at about -10.5 EV; that makes for 1.5 EV difference in the green channel alone.

It may be interesting to compare the flare on both setups.

[paulmoorestudio]

all I can say is wow, this test is very telling. thanks.  I too will have to test that sony out, but at this point it looks like another game changer.
Chris have you shot any motion with the 7r yet?

[Doug Peterson]

One would think if you were going to go through the effort of careful numerical analysis and judging relative image performance you'd do so with a set of images that were shot at base ISO for each camera. No?

Chris was nice enough to post a casual test from which you can glean some good general conclusions (like they are all very capable cameras). But it's probably misleading to draw detailed conclusions from them.

[EricWHiss]

I'm just looking at the images posted, but IMHO the IQ260 seems to have the most depth. The A7r and the Red the least. 

[ErikKaffehr]

Hi,

Well, both cameras have base ISO at 50. At ISO 100 DxO-mark measured 29 ISO for the IQ180 and 73 for. That corresponds to one stop. Phase backs seem to have a high ISO to protect the highlights.

Best regards
Erik

One would think if you were going to go through the effort of careful numerical analysis and judging relative image performance you'd do so with a set of images that were shot at base ISO for each camera. No?

Chris was nice enough to post a casual test from which you can glean some good general conclusions (like they are all very capable cameras). But it's probably misleading to draw detailed conclusions from them.

[ErikKaffehr]

Hi,

I happened to see some pretty bad staircase aliasing on the A7r that is not visible on the IQ 260. Check the top of the lamp cord.

Regarding the images I would say the dark areas on the Sony are clear and I would say the IQ is noisy, but as it has been pointed out by Ilias there is 1+ step exposure difference. The IQ 260 is significantly sharper, but I would assume this comes from megapixels and perhaps also from the pixels being larger.

I checked out the images in Capture 1, too. I still feel the IQ260 image is noisy.

Best regards
Erik

[Ken R]

When you expose to the left AND use non base iso on the phase backs that is what you get. Do the same test using iso 50 (on the IQ260, it is iso 35 on the 80mp models) and expose a bit more to the right (not much) and the shadows will be MUCH cleaner. The IQ image looks like what one would get with long exposures (in normal mode). Also which aperture did you use on the schneider 35? When you use iso 100 on the IQ backs its like cutting out 1 stop of data on the shadows side.

Color separation is best on the IQ file. The Canon is over saturating the reds everywhere it seems.

[MrSmith]

What about the cost factor?
A7r, metabones and a trio of 17,24,90 Tse lens (plus a Zeiss 50? Sigma 35 1.4 or 24-70 2.8?) =£?
Compared to iQ260, tech cam and a quartet of lenses =£?

[Paul2660]

This would be an interesting test for the IQ260 and the long exposure ISO setting of 140 which is the base iso for the long exposure setting.  Then compare it to the ISO 100 shot.

Paul Caldwell

[BernardLanguillier]

It is fascinating to see how an increasingly wider audience gets to realize the value of the Exmor technology as cameras equipped with those sensors decrease in price and become lens brand agnostic.

Cheers,
Bernard

[Iliah]

Hi Bernard,

Not sure a camera that records 1775 values per channel (less than 11 bits) can replace a digital back in all cases.

[JoeKitchen]

Something else to point out is that I have found that MFDB increase in color noise much more quickly than luminous noise when ISO is increased.  Whereas with CMOS based cameras, the opposite is true.  We tend to notice color noise more than luminous noise because it is, well, more noticeable. 

I am assuming we could increase noise filters in C1 and get ride of it, however this would decrease sharpness to an extent but probably not to the point where it is less sharp than the aR7 file. 

[BernardLanguillier]

Not sure a camera that records 1775 values per channel (less than 11 bits) can replace a digital back in all cases.

Hi Iliah,

Out of curiosity, how does that compare to a D800E/IQ280?

Cheers,
Bernard

[BJL]

Firstly, I agree with Doug; some of the close analysis attempted here would be best reserved for a comparison done with each camera at its best (base?) ISO speed setting. But thanks for this comparison too.

Anyway: Illiah, how is the EV scale defined on those histograms, and how does it handle raw output with different bit depths? If the histograms are counting EV's from maximum level down, the difference between 14-bit and 16-bit data would report the same numerical level with an EV difference of two stops. For example, a numerical level of 8 = 2^3 would be EV-11 relative to the top of a 14-bit scale but EV-13 relative to the top of a 16-bit scale.

Are the min and max values at right referring to the raw numerical levels? In that case, the IQ180 is actually giving absolute higher numerical levels, and the EV difference is merely a consequence of its 16-bit raw data having an additional two most significant bits, which of no relevance to the low-light region described in these histograms.

[EDIT: I do not understand that "blue clipping" at EV-14, from what AFAIK is a 16-bit signal: is that the existence of pixels with "0" value?]

[Chris Barrett]

This is definitely not a scientific test, but rather something that correlates more closely to my working methods.  In many cases it's just not practical for me to shoot ISO 50.  We often have people in our shots, are using strobe where multi-popping is counterproductive and occasionally shooting through a polarizer.

The Sony and Canon were shot at f/11 2 Sec Iso 100.  The IQ 260 was shot at f/8 2/3.  My initial exposure of 2 Sec just felt too bright on the IQ 260, so I used my 1 Sec exposure for the test.  When I process the 2Sec exposure to match the tonality of the group it DOES have better shadow noise, but the hilights don't clip as nicely.  I usually shoot to protect the hilights as much as possible (probably because I shot transparencies for 15 years).

Of course each of these images would only be at the very beginning of my postproduction flow and different techniques would be used to help each along.  All would have darker windows blended in.  I might revisit the brighter IQ260 file to use as a base and just as you can use darker exposures to recover hi lights, I sometimes use brighter exposures to clean up shadow noise (by processing them @ -X to match the base exposure and masking for just the shadows).

Perhaps the best test, for me, would be to proceed and retouch each to be the best possible image.

For now this tests has shown me exactly what I wanted to know...  The A7r can and will replace my 5d2.  While it won't replace my MFDB system altogether, it will take over some of that shooting.

Coming from years locked into shooting 4x5 Transparency film as the only possible workflow, I gotta tell ya, I'm damn giddy to have so many excellent tools at my disposal.

ps I've added the brighter IQ260 RAW file to the DropBox if anyone wants to play with that.

CB

[eronald]

As others have noted, This explains the 2 stops underexposure which Iliah is reading from the data for the Phase back.

In fact 2 stops underexposure will occur every time a back is used when set at 100 ISO (backs have no amplification, just use digital amplification). So 1 stop is lost from the "real 29" to the "fake "50 base ISO, and another is lost from ISO 50 to 100.

Of course an advantage of the back is that it can cleanly recover two stops of highlights in Raw.

Edmund

PS sorry about the redundant post I wanted to write this yesterday but sleep occurred.

Hi,

Well, both cameras have base ISO at 50. At ISO 100 DxO-mark measured 29 ISO for the IQ180 and 73 for. That corresponds to one stop. Phase backs seem to have a high ISO to protect the highlights.

Best regards
Erik

[ErikKaffehr]

Hi Chris,

Thanks for posting!

Regarding scientific tests, DxO does that better than most of us.

Best regards
Erik

This is definitely not a scientific test, but rather something that correlates more closely to my working methods.  In many cases it's just not practical for me to shoot ISO 50.  We often have people in our shots, are using strobe where multi-popping is counterproductive and occasionally shooting through a polarizer.

The Sony and Canon were shot at f/11 2 Sec Iso 100.  The IQ 260 was shot at f/8 2/3.  My initial exposure of 2 Sec just felt too bright on the IQ 260, so I used my 1 Sec exposure for the test.  When I process the 2Sec exposure to match the tonality of the group it DOES have better shadow noise, but the hilights don't clip as nicely.  I usually shoot to protect the hilights as much as possible (probably because I shot transparencies for 15 years).

Of course each of these images would only be at the very beginning of my postproduction flow and different techniques would be used to help each along.  All would have darker windows blended in.  I might revisit the brighter IQ260 file to use as a base and just as you can use darker exposures to recover hi lights, I sometimes use brighter exposures to clean up shadow noise (by processing them @ -X to match the base exposure and masking for just the shadows).

Perhaps the best test, for me, would be to proceed and retouch each to be the best possible image.

For now this tests has shown me exactly what I wanted to know...  The A7r can and will replace my 5d2.  While it won't replace my MFDB system altogether, it will take over some of that shooting.

Coming from years locked into shooting 4x5 Transparency film as the only possible workflow, I gotta tell ya, I'm damn giddy to have so many excellent tools at my disposal.

ps I've added the brighter IQ260 RAW file to the DropBox if anyone wants to play with that.

CB