What's the real bit depth of Epson V700?

[Rudeofus]

According to the Epson data sheet they produce 16 bits for each color channel, but is this really what the sensor produces in terms of actual information? Does anyone have actual numbers, or does anyone have a V700 scan (as 16 bit TIFF) of a very uniform grey area so I could do the math?

[pellicle]

Hi

what matters is ones ability to tune the analog sensors input levels to match your AD converter. This needs to be done on specific films and is something that can't be done on a flatbed. I'm guessing that the Epsons are tuned to put their white on the calibration reading and their black at their dmax

I've tested all my Epsons with a Stouffer wedge and seldom does the DMax go as dark as them.

you may find the following helpful reading, note that the 4990 (probably the closest to your 700) does not significantly penetrate into the deep black of the stouffer better than the 3200


http://cjeastwd.blogspot.com/2009/04...e-testing.html

http://cjeastwd.blogspot.com/2008/03...nners-for.html

essentially its a non-question (and rather like asking if a Ferrari is faster than a Lambo) as only drum scanners have the ability I mentioned above and the older ones were often only 8 bits per channel anyway.

I think there is a good case for arguing that a well captured 8 bits provides plenty of leeway for adjustment without posterisation and the main pressing need for 16 bits is in hardware which can not be tuned (such as any flatbeds I can think of {anyone know if you can set hardware levels on the Creo?}).

I think that you will get more from learning to drive the V700 series well than fretting about specs of these. They are good tools for the money.

I await some scans back from a friend with a Flextight X1 to make objective comparisons to my 4990

stay tuned for that one

[Loris Medici]

pellicle, I don't understand this. Do you indeed say that a well captured 8 bit file provide enough room for adjustments just as a 16 bit file!? Not so in IME, especially in the context of b&w film; think of the levels and gamma adjustments you have to do just to linearize the raw scan. (= The absolute minimum manipulation.) That brings us to the natural conclusion that hardware 8 bit is pretty much a [POOR] figure too. (Drum scanners are different animals; they usually can see grain, and at that level you don't need much bit depth. Plus, they can do multiple passes by design, increasing the effective bit depth...)

Regards,
Loris.

...
I think there is a good case for arguing that a well captured 8 bits provides plenty of leeway for adjustment without posterization and the main pressing need for 16 bits is in hardware which can not be tuned (such as any flatbeds I can think of {anyone know if you can set hardware levels on the Creo?}).
...

[pellicle]

Loris

Do you indeed say that a well captured 8 bit file provide enough room for adjustments just as a 16 bit file!?

yes, that's what I said. Chances are however that unless you are tuning your hardware at scan time to set that analog gain of your photo-receptors to the black and white points of the media and then dividing that among the 8 bits per channel you are not going to be able to do it.

I have had a number of scans done which were returned to me as 8 bit tiff files, I have then done some adjustments on these files and subsequently converted to another profile, I saw no evidence in the prints I got to have "ahhah, posterisation banding" jump out at me.

If you are doing large adjustments I would argue you did not scan it perfectly.

It is important to keep in mind what I said and not take this to an extreme and remember I said well scanned.

Yes, I know we have been taught to perfer 16 bit, but after I've cleaned up an image and got it how I want I will often convert it to 8 bits (but only if I'm sure and I've flattened the image of any layers).

for instance I have scanned this image (not this file, but this image)

and after being satisfied with it have flattened it and then sent it off for printing. Didn't like the contrast, adjusted a wee bit and printed again to my satisfaction and can't tell the difference.

same with this one (scanned on a eversmart flatbed I suspect)


printed, tweaked and reprinted (this time not to my satisfaction) but with no evidence of posterisation.

If you want I can roll up that last one and post it to you as I'm moving back to Australia and may as well give it away (its 77cm wide). Plop me a couple of euros postage and I'll whack it in the mail for you

[pellicle]

PS I am not recommending you scan in 8 bits, especially with most consumer type scanners. Nor am I saying that 8 bits is better to edit than 16 bits (though it can make RAM requirements lighter on big images).

PPS

if you examin arguments like on this page http://jtrujillo.net/digital-photo-tutorials/8vs16bit/

you will find their proof of 16 bit advantage in quite severe adjustments:

like he does this to the image:



then undoes it with:



whoa, I'm not likely to do such wild adjustment to any of my images ... no wonder he got banding

[Loris Medici]

It's understandable to convert finished/manipulated files to 8 bit, "ONLY for sending them to the lab for printing". I would always keep the 16bit master file.

For small manipulations (like your suggestion above: small/fine tweaking) 8 bit files could do the job indeed. BUT, I'm talking about raw scans from B&W film, 1) linearization and 2) manipulation:

1. Think of a pyro developed B&W negative; those aren't dense, you'll often have to do a pretty strong levels adjustment, even in case of PERFECT exposure. Then you'll have to linearize the tones which involves a pretty severe gamma correction.

2. Burn/dodge/local contrast adjustments with masks and what not with several layers. (That's how I work...) In that case you'll often notice a drop in quality if working with a 8 bit source. And sometimes you indeed have to do severe LOCALIZED adjustments, not every adjustment has to be applied to the whole file...

Sorry, I'm not convinced at all; I will continue to scan and work in 16bit mode and I definitely don't recommend anyone else to do otherwise. It's pointless unless you have a pretty poor system by todays standards.

Regards,
Loris.

[pellicle]

Loris

Sorry, I'm not convinced at all; I will continue to scan and work in 16bit mode and I definitely don't recommend anyone else to do otherwise.

I appreciate that english is not your native language but I was not trying to convince anyone of anything; to wit I actually stated:

I am not recommending you scan in 8 bits, especially with most consumer type scanners.

perhaps that was not clear enough ... I will repeat it again more clearly

I am not recommending you scan in 8 bits

I hope that clears up my situation

[Loris Medici]

I don't say that you recommend to scan in 8bit anywhere...

My objection is completely towards your original statement: "...I think there is a good case for arguing that a well captured 8 bits provides plenty of leeway for adjustment without posterisation..."

This could (actually will) lead unknowledgeable people to use 8bit files (in capture and post-processing) which is totally bad practice. Besides, frankly I think there's nothing to argue about it...

Regards,
Loris.

[sanking]

My Eversmart Pro makes the analog to digital conversion in 14 bit but the software only allows 8 bit saves. My work procedure for this scanner is to make as many corrections as possible in the pre-scan so that all of the very abrupt tonal transitions are done in the high bit scan. I then save the file as 8 bit, but immediately convert it to 16 bit before doing any final corrections or changes. Converting an 8 bit file to 16 bit will not add any new tones, but it will prevent losing any of the existing tones when making additional corrections. I get very good results with this workflow scanning LF negatives in grayscale.

BTW, with the Eversmart there is nothing to be gained by scanning a B&W negative (not stained) in RGB as there is virtually no difference in grain or sharpness in the three channels.


Sandy King

[pellicle]

it will be nice when we can make adjustments in floating point rather than integer maths ...