Fujifilm X-T100 Photographic Dynamic Range (PDR) at PhotonsToPhotos

bclaff wrote:

tradesmith45 wrote:

... For the X-T100, the Shadow Improvement chart shows little shadow improvement

This nearly flat line indicates that the sensor is ISO In-variant:

w/ higher ISO & the Read Noise charts show much higher noise compared to say an X-T20 or X-T2.

As I stated in the original post, and as is evident by the Read Noise in DNs :

The X-T100 does not have dual conversion gain so it does not get the read noise improvement at ISO 800.

Would it be correct to conclude the X-T100 will have much worse S/N for astro imaging than the other 2?

I'm not sure it "much" more. PDR certain falls further behind at ISO 800 and above.

So does a Shadow Improvement of less than 1 EV mean the shadows are suppressed at higher ISO (to reduce noise)? The Canon 6Dii shows much higher than 1 EV shadow improvement w/ higher ISO.

No. Shadow Improvement is primarily indicative of how much read noise is upstream/downstream from the amplifier. The X-T100 is "ISO In-variant" whereas the 6D Mark II is not.

Regarding your request for RAW images for measuring fixed pattern noise, I have an X-T10 similar but not the same as an X-T1. Is that helpful to you?

No. I'm looking for exactly those models.

Is fixed pattern noise included in the read noise charts?

Yes. Read noise is as observed so Dark Signal Non-Uniformity (DSNU), a form of Fixed Pattern Noise (FPN), is included.

The FPN test is summarized on the Sensor Heatmaps page (nothing to do with heat, this form of visualization is called a heatmap.)
For example, here's the X-20 :

Best viewed "Original Size"

The false color is simply to help you see if there are any patterns.
The illuminated test does show some horizontal bands; not bad though.

My simple comparison of FPN - a 2 & 4 min. dark frame boosted 4EV during RAW conversion- shows a substantial difference between the XT10 & my XT2 w/ the later showing fewer pixels w/ FPN but they are much brighter.

In my test the X-T10 looks more vertical while the X-T2 more horizontal.

Best viewed "Original Size"

Thanks Bill for the reply.

Let me restate what I think you're saying & what the data says regarding use for astro.  I'll use XT100 vs XT20.

Single stage amplification & invariance means the XT100 probably should be used differently from the XT20.  To match read noise levels (not always important for astro when shot noise dominates), the XT100 must be set to ISO 318 & boosted in post to match the XT20 @ ISO 800.  At ISO 318, the XT100 will have a bit more DR but less?? shadow detail?

This is an area where translating from detailed data to practical visibility can be difficult.  Having to struggle more to reveal shadow detail & retain star color for my XT2 compared to a rented XPro2, seems to me differences around 0.5 EV are meaningful for astro.  But this also brings up issues of copy variation & measurement error.  For example your charts of Shadow Improvement for an XPro2, XT2 & XT20 are slightly different - are those differences meaningfully accurate?

Regarding FPN, its not clear to me that the short exposure test you use for read noise reveals the types of problems encountered with astro & much longer exposures.  For example a comparison of FPN from the D5300 & D7500 over at Stargazers Lounge reached the opposite conclusion (D5300 better) from what your Sensor Heat map data shows.  Your comments here would be helpful.  I use your info often & simply want to understand the meaning.

Here's my dumb (uncalibrated for black point) comparison of my XT10 & a rented XPro2. I can maybe see the horizontal vs vertical difference.  In practice photo terms, the long -2-4 min.- exposures I use for starlit landscapes from the XP2 are fewer but more obvious compared to the XT10.  I more often have to clone these out from my XT2.

Thanks again.