Fujifilm X Cameras: Using the ISOless Sensor

Last time out we looked at the ISOless sensor and demonstrated how it worked.

To recap on that; basically if you turn the ISO up in the camera, it makes the resultant image brighter.

Or APPARENTLY, if you prefer; you can shoot at a lower ISO and turn the brightness up yourself when you work on your RAW file

Possibly you’re thinking, ‘well all roads lead to Rome’

Indeed.

The thing is… it’s not quite that simple.

Excessive noise reduction is (in my opinion) well controlled on the X-Trans sensor, but owners of cameras with a X-Trans II sensors have to put up with details being smeared by excessive noise reduction.

Admittedly this is mainly a SOOC jpeg problem, but although RAW data is just that (RAW data), it does contain a great detail of subsidiary information… Obvious stuff like which lens, what camera etc but it also contains information about the exposure of the shot, whether or not you used any dynamic range settings, how much noise reduction may be required etc

Now in real terms, the only reason you’d want to raise the ISO when taking a shot is if the shutter speed was too low for the situation, perhaps you need to freeze movement, or perhaps the shutter speed is too low to be hand held.

It’s these situations that make us sacrifice the superior image quality and dynamic range of base ISO and select a higher ISO

The apparent trick to the ISOless sensor is that we could use a lower ISO, get the benefits of this, yet still use a higher shutter speed.

So for the next test, I did the following:

Here the ISO6400 shot has exposure parameters chosen by the camera, which I’ve then manually replicated whilst dropping the ISO, then compensating on the computer by raising the brightness via the exposure slider.


6400 0EV


3200 +1EV


1600 +2EV


800 +3EV


400 +4EV


200 +5EV

As we discovered last time (especially at these resolutions and with photobucket hosting) it’s all SEEMS pretty much a muchness!

So let’s get closer






Suddenly it’s not clear cut is it?!

It’s still quite close… and the ISO200 does PERHAPS have a tiny bit more detail, but it also has a lot more noise.

It’s also complicated by what which RAW processing software you use…

I did these in LR, because it offers 5 stops of EV adjustment, and I needed 5 stops of EV adjustment 🙂

I tried the same in a different (and I have to say a PERSONALLY preferred) piece of software and at +5EV the image completely fell apart!!

This complicates matters… because different RAW convertors handle things in different ways, they act upon (or completely ignore) the metadata from the camera that’s burnt into the .RAF file.

So, to my mind, it’s not as simple as set up the exposure triangle as if you were on the highest ISO, then set the lowest ISO, and sort it all out when you get home.

Plus, let’s be honest – pushing files 5 stops is nearly always going to lead to some quality problem or another…

So for what’s it’s worth, my PERSONAL OPINION only, here’s how I use my ISOless sensor…

In a word: “sparingly”








The above shots show EV push of 2 Stops in pairs.

800/200 + 1600/400 + 3200/800 + 6400/1600

I use the ISOless sensor in conjunction with the EV dial. (If I’m using aperture priority mode, if I’m in full manual, I just do the maths in my head, ISO/Shutter Speed is only division or multiplication by 2 after all!)

That offers the following advantages

I can just turn the EV wheel to a negative value to raise the shutter speed

If I’m using a RAW convertor that reads EV values (and I use more than one RAW convertor, so it pays for me to have a universal setting) then that convertor doesn’t mind me telling it to add +2EV in post. If I’m using one that doesn’t read EV values, then it’ll still let me push +2EV in post

That’s why all the shots above are only pushed 2EV. But also another reason, that I’ll come back to later in this page.

Why -2EV? well that’s as low as the dial goes on the X-Pro1 (On the X-T1 and other Fuji X cameras, it goes to +/-3)

Why select a minus value, when I want a brighter image?

Well I do (want a brighter picture) but at the time I want a higher shutter speed, which means turning the wheel down! (Not up)

And there’s another thing as well…

Remember my article about Automatic Dynamic Range, and why I don’t use it?

If you look closely at the images pushed 2EV above. You’ll notice that it’s only ISO1600 that’ll take +2EV without some loss of quality…

That’s because the X-Trans and X-Trans II sensors use a mixture of ANALOGUE and DIGITAL gain (gain = increase in the brightness) not arriving to a full digital gain solution until after ISO1600

It’s the analogue data that’s set into the RAW file. This amplified data is placed before the Analog-to-Digital Conversion (ADC) process.

The full ‘nuts and bolts’ of digital image creation are too complex (and a little off topic) to go into here…

As previously noted, when we raise ISO, we drop quality (namely dynamic range and resolution).

Basically, the ISO amplification (on X-Trans and X-Trans II) between 200 and 1600 is inserted BEFORE the RAW file is created. This means that if you clip data, by shooting at 200, but with exposure settings for 6400, then this data is lost. If you attempt to push this file in post, you’re just amplifying clipped data.

At ISO1600 and beyond, the camera is DIGITALLY amplifying the POST ADC data (the same as you dragging the exposure slider on your computer)

It’s worth mentioning that you MIGHT very well get a nicer file, shooting at 1600 and pushing 2 stops, than if you select ISO6400. This is because the camera will include noise reduction data for 6400 in with the .RAF file, and you might want to handle noise reduction yourself in post. (For example, this why on X-Trans II cameras, skin gets unnaturally smooth after 1600. If you shoot SOOC X-Trans II jpegs, I highly recommend using ISO1600, with -2EV on the EV dial, then using the in-camera RAW convertor to push the file +2stops. Obviously, you’ll need to be shooting RAW + jpeg to do this)

So is the sensor truly ISOless?

Yes! But with the caveat that the first 3 stops of digital amplification are burnt into the metadata before the RAW file is physically created, and pushing clipped data might very well not exceed the quality of letting the camera do it.

Of course, (as we saw) you can get a bit more resolution from pushing ISO200, but at the expense of noise…

The ISOless sensor (in the incarnation within the X-Trans and X-Trans II cameras) is not some piece of unworldly magic, allowing you to run around at night shooting at settings that require sunshine.

You can’t 100% completely set the ‘ISO’ when you get home. At least not before ISO1600.

So for me?

On my X-Pro1 and X-T1, I leave auto ISO @ 200-1600, if the shutter speed is too low (and the ISO is at 1600), I bring it up, by using a negative EV dial setting, then brighten the file in post.

But before the ISO reaches 1600, I let the camera provide the signal amplification.

======================================
PREVIOUS PAGE
NEXT PAGE

A lot of time and effort goes into this site.. If you like what you see, and/or if I’ve helped you then perhaps you’d consider helping me?

One way you could help me is if you want to buy ABSOLUTELY ANYTHING from Amazon, (that’s anything; cameras, books, shoe polish, whatever) if you do so using the links below, then I will receive a small percentage of your expenditure, and you will pay NO MORE than you would have paid anyway.

Amazon USA Any Product

Amazon UK Any Product

This will also work if you USE THOSE LINKS to click through to your own country.

To do this, click a link above, scroll to the bottom of the page, then select your country from the drop down menu, as shown below

Another way you could help, especially if you don’t like Amazon, but do like me, is by making a donation

The donate button is in the top right hand corner or can be found on the link below

Thanks Very Much!

Donate
======================================

The X-Pro Series Content: Referenced and All In One Place

Back to Page One

Back to Page Two

Back to Page Three

Back to Page Four

Back to Page Five

Back to Page Six

Back to Page Seven

Back to Page Eight

Back to Page Nine

Back to Page Ten

Back to Page Eleven

Back to Page Twelve

Back to Page Thirteen

Back to Page Fourteen

Back to Page Fifteen

Back to Page Sixteen

Back to Page Seventeen

My Blog Click Blog Table of Contents

Other Stories Click Pages and Articles

Advertisements

2 thoughts on “Fujifilm X Cameras: Using the ISOless Sensor”

  1. Not sure if I’m missing something here. You discuss setting the EV dial but surely this is disabled when shooting in manual control. Good article by the way.

    Like

    1. Thanks Steve,

      The final words of that article read:

      On my X-Pro1 and X-T1, I leave auto ISO @ 200-1600, if the shutter speed is too low (and the ISO is at 1600), I bring it up, by using a negative EV dial setting, then brighten the file in post.

      But before the ISO reaches 1600, I let the camera provide the signal amplification.”

      So if the camera selects ISO1600 AND a SS of 1/30 (ie in aperture priority mode) & I think ‘Hmmm I don’t fancy hand holding that at 1/30’ then I’ll dial -2 EV on the EV dial and the SS will rise to 1/125, then in post I’ll lift the shadows or apply a +2EV exposure boost (with the exposure slider) or sometimes a bit of both 🙂

      Hopefully that explains.. If not, let me know

      Adam

      Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: