Should I trade in my P45+ for the new back? Yes or no? and Why besides the obvious screen and BS dynamic range increase (I don't believe it ).
I wouldn't "believe" the increase in dynamic range on blind faith. I would instead suggest you have a Phase One partner provide you the opportunity to do your own testing (in whatever your normal shooting environment is). Because it is a reality; the increase in sensor quality (color, tonality, dynamic range, shooting speed) since 2005 when the KAF-39000 sensor was released are real (wouldn't you be surprised if that weren't the case). You can read a bit about the sensor in the IQ260
here. But the only meaningful way to evaluate that is not a numeric comparison (X stops vs XX stops) or another user report, but to go take pictures (relevant to your intended use) with both and make your own evaluation.
Since you haven't given us any information about what you shoot, how you shoot, or what you consider important. So here is a fairly comprehensive list of other advantages that may or may not be relevant to your needs:
- more resolution, 60mp rather than 39mp. This gives you additional flexibility to print larger, crop tighter, use verticals from horizontals, pull "detail" shots from "overall" shots (i.e. pull a headshot from a full-length shot)
- No issues with firewire power on iMacs/Laptops**
- Ability to sync at 1/1600 when using DF+LS lenses***
- Long exposures are taken at a base ISO140 rather than base ISO50; shooting an architectural scene at dusk might take 20 seconds rather than 60****
- Camera control when tethered (AFD1/2/3, AF/DF/DF+)
- Faster readout
- Sensor+ for higher ISO, faster shooting, smaller files (15mp up to ISO3200 up to 1.4 frames per second)
- Larger sensor (1.0 crop rather than 1.1 crop), makes your wides wider and your wide-open shots shallower in DOF (assuming you frame the same image)
- Subjective opinion (shared by nearly all our users that have transitioned): smoother tonality, better color especially in skin tones and subtle greens
- graphical or numerical readout of horizon and pitch through user interface, accurate to nearest 0.2 degrees
- one-click correction of horizon and perspective in C1 for one image, or for many images at once
- focus mask in-back, especially useful for fine tuning focus or very fast differential focus comparison (think an eye doctors line "better on A, or B")
- accurate 100% review on the LCD, of all images when shooting untethered, or for the more recent 10 images when shooting tethered
- built-in wifi for wireless review on an iPad/iPhone/iPodTouch without tethering. Might be useful for you, an assistant, an art director, a stylist etc. This includes the ability to rate the images (which will show up in Capture One downstream), check 100%, control and trigger the camera, see a histogram, and either show images as they are shot, or review past images as you continue to shoot
- adjustable highlight warning level
- highlight warning can be set to flash in the thumbnail next to the larger-unimpinged image (allowing you to quickly notice when you are blowing a highlight without interrupting your view of the overall image)
- a Thumbnail view allowing you to quickly scan through many hundreds of images
- IIQ-S (the lossy compressed format) is improved, making it a relevant tool in more situations. This reduces raw file size by 40-60% with only a very minor change in image quality.
- adjustable grids and guides on the LCD
- customizable splash screen (very minor point, but a "nice touch" to see your logo pop up on set)
*USB3 is in final beta testing now for the IQ1 (available to users via their dealer) and is already active in the prototype IQ2 models.
**With a P+ back you are sometimes required to run off the back's battery power during a tethered shoot. This occurs when the laptop/iMac doesn't produce sufficient/consistent firewire power
***P45+ is limited to 1/800
****Both backs require a dark frame after exposure