Raw histogram and why does it matter

I shot 3 images in a controlled studio situation with uncompressed , lossless and compressed. processed them in ACR saved as psd files and the file size was exactly the same at 187 meg for all of them. so if compressed is suppose to not regain some of its information then why has it saved as the same file size ?

You are correct. This is because you are hitting the Auto-ISO lower boundary with DR400.
DR400 is like shooting with -2 EC and then lifting in the post. If Auto-ISO lower boundary is not hit, it will lower only ISO (internally) and keep the exposure constant.

I also see what you are observing: Adobe lifts everything, including the highlights. However, the highlights data is still there in DR400 mode, whereas they may be lost with DR100 (same effect as when shooting with negative EC). Unlike JPEGs, where the highlights are automatically "preserved," with Adobe you need to do it manually (highlights slider or masking).

im mainly a portrait shooter and focusing on skin tone exposure is most important. whether the white background is white doesnt matter it can be easily fixed in post. and also lets be very clear the white background has be at aprox 245 not pure white 255 as when you print your printer NEEDS to lay ink on the whole image. the perfect exposure has nothing to do with technical jargon of where the white point or black point lands. the question still remains a mystery in the title of my thread, because everyone is different and has different objectives.

whether the white background is white doesnt matter it can be easily fixed in post. and also lets be very clear the white background has be at aprox 245 not pure white 255 as when you print your printer NEEDS to lay ink on the whole image.
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When you say "printer" are you referring to a physical ink jet printer or a commercial printing house?

Rich

RD only shows the total exposure range , it places the total exposure information of your image in a position on the scale where EV0 is equal to 12% mid grey which is calculated from your image. it doesnt show what correct exposure is. use ACR for that ,there is NO correlation between RD and ACR histograms.

I think we both know how this works. The point is, when there is plenty of light for DR200 and base ISO, it is a pretty bad idea to walk around shooting normally, but at DR400 all day instead (and that goes for raw or jpeg shooters). A DR mode with (often significant) positive exposure compensation can often brighten up the mid tones of a jpeg in very high DR situations without blowing the highlights - which is indeed putting the feature to good use (and will reduce any sensor exposure deficit), but I think more than a few people just think. "great, more dynamic range, I'll just shoot in DR400 24/7, win, win right? No, not so much, IMO.

The highlight detail will "be there" in either case if you expose correctly, but some additional noise might also also "be there" with the DR400 file (unless, of course, you shoot at DR400 with +2 stops of exposure compensation - which will produce a functionally identical RAW file to shooting at base ISO and DR200 and 0 EC).

I've experimented a bit shooting jpegs with the DR modes and have found DR200, usually with some positive compensation, to be quite effective for producing well balanced SOOC jpegs in high DR situations. There might be exceptions, but I think DR400 generally produces overly dull results, even in extreme light. IMO, a high DR scene photo typically ought to look like a high DR scene.

Have you not read anything already posted about the "EV 0" scale? It is typically positioned at -3 EV relative to where the clipping threshold is. In my examples I moved to " EV 0" scale to coincide with the clipping threshold instead (I don't care where the mid tones are, I always expose for the highlights). It is the immovable scale on the bottom of the histogram that is relevant for determining the exposure (typically clipping at around 16000 for 14 bit RAW files). The RAW histogram absolutely shows whether your RAW exposure is correct (if you actually know where you want your exposure to be). ACR does not.

He has not read anything and does not understand that where in your final image the mid tones fall are a function of how you process your image.
And still does not understand that if you are do not have any highlights to clip in your image you can further increase your exposure and adjust mid tones that could now be 1 to 2 stops above 0EV back into those 12% grey tone is located in his final image

Your quote: It is typically positioned at -3 EV relative to where the clipping threshold is.
which is 12.5% grey calculated from YOUR image.

It saddens me that, after hundreds of posts on the subject, that this is almost completely wrong. If you want to check exposure, you can ignore the EV scale and just look at clipping or lack of same. RD will let you know if you've made the correct exposure for the ISO setting you've chosen. ACR is a terrible way to detirmine what the correct raw exposure is.

I don't think we'll ever reach closure in this thread.

it saddens me that you cant post an image to prove your theory

Its even more depressing that this has been shown to you many times and you just ignore them all.

I should have left this thread when you referred to many in this post as students when the teacher should have taken the 1 hundreds of post telling you otherwise

🤣😂🤣😂🤣😂😂

RD is set for 12.5% that 12.5% is calculated from the image in question and positions EVO there.

I think it's pretty clear why DonaldB still doesn't get it after 100s of posts.

He has made it clear, either in this thread or others, that he is mainly a sooc shooter and that is fine.

It also appears that his idea of exposure is simply just how light or dark an image looks, nothing more nothing less.

As long as the image lightness is acceptable and highlights are not clipped then he is happy.

All that is fine and many photographers are the same as it is their choice to make. But DonaldB not being a raw shooter is struggling to understand and cope with the fact that by maximising the quality of the raw data it is possible to create images of higher quality than sooc jpegs.

He also clearly has misconceptions about raw histograms, the information displayed and how RawDigger works.

Until he accepts there are potentially additional benefits when processing raw data compared to sooc jpegs this thread will continue to go round in circles.

What's the reason to pay attention to EV0 when trying to determine if you got the exposure right? It's obviously confusing you. Just ignore it.

It isn't.

there isnt a reason as exposure is subjective and Illiah 12.5% is also subjective because majority use 18%

I know its 12.4999 % so my bad you are correct in your statement 🙄