Color reversal films generally do not push or pull gracefully. Weird things can happen to the 3 layers causing some unpredictable results.
That said, IDK if the following is true today but at one time some Ektachrome 100 films were comparable Ektachrome 200 films with 0.3 neutral density dye added to the coating. This dropped the speed from 200 to 100 and gave an incredible increase in sharpness while everything else stayed the same.
Provia 400X for example is excellent pushed to 800 and 1600, and even quite good at 3200.
And excellent pulled 1 stop.
It pushes better than the current 400 CN films.
The film is specifcally designed for push processing.
This film belongs to the best color films ever made.
Astia 100F and Provia 100F deliver also excellent results pulled 1 stop and pushed 1 stop.
Apparently some of us have very different standards about what consitutes acceptable quality. I consider the current Provia film useless for pulling, and Astia
maybe 1/2 stop at best. The whole point of pulling is to SLIGHTLY expand the exposure range of the film without gross crossover or lumping of the extreme ends
of the curve. Otherwise, you're merely trying to salvage a bad exposure. I could pull
the older-style Provia 100 half a stop with just a little blocking up in the highlights,
and get better shadow expansion; but the 100F has very little forgiveness in this
respect. I will admit that I haven't tried the 400-speed film because I shoot mostly
8x10, and that stuff penalized your wallet heavily if you waste an exposure. Pushing
virtually always ends up lopping off part of the scale. It's basically a form of underexposing, losing shadow values, and then trying to correct the midtone saturation; but if that's the look someone wants...
Pushing reversal films is achieved by essentially fogging the film so that the color Dmax is decreased by the increase in first development giving fogged silver that does not give a dye image. There s thus a reduced Dmax in the final color image which gives what appears to be higher image speed but in reality is no speed increase at all. If the layers are not perfectly balanced, then the image can shift color, have color crossover and often will give very poor results.
Of course, it also changes the mid scale contrast and the grain.
So, given what you have said, I would say that the user must be the judge of what is acceptable for them and I would advise them to proceed cautiously on this.
Also, you have taken part of the line from my post out of context which changes its meaning somewhat.
Provia 400X is a good slide film for pushing, it is otherwise not a good film for pushing.
Regardless, it colour corrects fine if used as a non-final product, all the shadow detail you could possibly want, all the highlights are there (as the pull was a little too much), contrast actually seems fine, but the saturation and punch is gone.
Last time I did something like this it was a cross-process in C-41 combined with a pull just to get the images off the film, colour corrected the results were much better and much more strongly saturated - you generally don't intend for low saturation when pulling out slide film.
If you have good process control, I'd certainly prefer pulling to flashing the film, which tends to spoil the sharpness and differentiation of the shadows. But I gave up both once Fuji came up with a triad of films for different contrast situations (Astia/Provia 100/Velvia). Now that the selection of these films has become limited again (at least for me, in sheet version) and Kodak color neg films have been dramatically improved, it's a whole new ballgame.
There is no color shift and color crossover pushed at 800 and 1600.
Grain is almost the same at 800 compared to 400. You need a 12x loupe to see the very small differences.
At 1600 grain is coarser, but still very fine.
@athiril: Provia 400X has much better sharpness and higher resolution than Portra 400, at normal speed and pushed.
The difference is big, 20 - 30% depending on the used speed.
And Portra 400 is even worse in this respect compared to Pro 400H.
I've done direct comparisons.
If it works for you then my best wishes. My statement was a generalization and also phrased in the conditional tense using the lead in "IF". So, IF Fuji has balanced their reversal films better now, then my statement obviously does not apply.
I'll stand by what I said though and that is that reversal films do not push or pull gracefully when compared to negative films. This is a generic characteristic of reversal films that I learned from many years working on the design of films, emulsions and processes.
Despite all claims made about about push/pull processing, very few of the surviving E6 lines I've used recently are capable of consistent monitoring of processing times--the key to satisfactorily consistent results. Sad but true. I love shooting 120 E6 material(especially E100GX)but haven't gotten nice results from pushed Provia 400 in a very long time.
I'm not sure what Film-Niko's up to here but with the realities of hybrid workflow, Portra 400 makes my life way easier for not sweating iffy E6 processing.