The company published some of the maths behind their product. I used it as starting point for my own project, along with some stuff from Arri and Kodak. I think the Photoshop inversion is just (1-X) where x is normalised value of the negative scan, that is just a guess, but if it is poor then that is probably why...
I went through each of the scans that ken posted, I first converted them to a gamma of 1, and measured each step. I can't seem to post the spreadsheet, they all show a reasonably linear response from the CCD, it is less linear towards the bottom of the scale. I think the vuescan exposure is clearly better, it gets you further away from the noise floor, and the response is more linear away from the bottom of the scale. Can you tell the difference in a real print? I don't know! I suspect maybe with colour, where poor accuracy in the highlights would result in colour casts.
Yes Ian, you are right, first is downloading last drivers and reinstalling.
Anyway an abnormal noise may happen when stepper motors cannot move the carriage because it is blocked, perhaps if the scanner was operated while it was blocked it could happen than a wheel jumped a tooth or something like that, resulting in a missalignment. I would remove the bed glass and I'd inspect what happens, then I'd free mechanical links to see if a section of the mechanical chain of the drive is mechanically blocked, or perhaps some dry teflon lube can solve it. Because the noise, it may be a mechanical issue easier to DIY fix.
Randy, you are right, V850/800 have same performance, avoiding the warmup is convenient, but IMHO there is another advantage, LED illuminators are very stable requiring little or no calibration overtime, if one wants the scanner calibrated. Lamps of the V700/750 (I guess) can change illumination a bit at the beiginning, then there is a more stable level during several thousands of hours, and by end of life of lamps again we have changes in the illuination's level and hue.
My V750 came with an IT8 calibration slide, the V850 came without it. Perhaps with saving the cost of the IT8 target they can fit the LEDs , well, and sure today leds are cheaper...
The scanner makes the unpleasant sound as soon as the power switch is turned on. It's not a software issue as far as I know.
I guess I need to open it up and see if there's anything obviously wrong. I'm not particularly good at repairs.
Ken, sorry to hear about the V700. Not sure if this helpful, but I think you are on a mac platform. I recently installed High Sierra and it caused a problem communicating with a 4 year old Epson all-in-one printer/scanner. Normal wireless installation of the printer is no longer possible, and it needed to be installed using a fixed IP address. I now use this all-in-one device wirelessly using the fixed IP address. EpsonScan no longer functions using this connection method, and Apple ImageCapture is the only way to utilize the scanner for simple/everyday things.
I use my V750 with a USB cable. While on the surface this may seem apples and oranges, as mentioned above, the drivers and connectivity could be the issue. I would also add that any OS updates done recently can be problematic, if you are using mac. The recent update to High Sierra was also somewhat painful to install, after a very painful High Sierra installation.
I don't think it's not a software problem. The scanner worked fine while I was doing tests. Then it just stopped working after no changes were made to anything. It can only be a mechanical or electronic failure.
Last edited by Ken Lee; 14-Jan-2018 at 09:33.
Just a thought...
There are two "zero position" sensors for homing, one is for the sensor carriage and the other is for the illuminator carriage, perhaps when "powering on" the scanner reaches the mechanical top without sensing the zero position, and thus trying to go beyond, so the stepper motor would make that noise because it could not rotate.
First try to see if the noise comes from the under bed drive or from the illuminator drive in the cover. Then locate the "end of travel" sensors that should tell the control electronics that a carriage its at home. The scanner uses those sensors to find a known starting position, from there it can count steps to place the sensor and illuminator in the wanted position. I don't know what kind of sensor is it, but for sure you have 2 there...
There several videos in youtube explaining V700/750 disassembly for cleaning https://www.youtube.com/watch?v=z7QkfM5TQ4A
Anyway if you find that a carriage tries to go beyond a mechanical end it would be worth to repair it, because probably parts to replace are simple.
I have done that with Stouffer 31 step wedge. Shows greater than 3.05D for Epson V850.
Post number 37 http://www.largeformatphotography.in...n-target/page4
Bookmarks