I would like to increase contrast make it stronger / darker with TAX 400 Film but keep developing time standard. Do I have to push this film or underexpose it? If underexpose then by how much?
I would like to lose shadow details and create hard contrasts in negative and really dark black colour. Is it a right film to do so? Since i scan the negatives I can not increase contrast in print.
Thank you!
You cannot change the contrast of the negative without changing the amount of development.
Further, the amount of contrast control available for T-Max films is limited -- only the P3200 is made to accommodate significant changes in contrast ("push") to simulate a 3200 ISO speed (the native speed of that film is about 1000). T-Max 400 has a relatively limited amount of "push" available.
In general, however, to lose shadow detail, you would expose less. This is commonly combined with developing more than standard (which you can request at the lab, if you're not processing the film yourself) to give mid-tones similar to a correctly exposed negative. If you just underexpose and then give normal development, you'll get negatives with lower than normal density; depending on your scanner you may or may not be able to bring the tones back to your usual mid-tone range.
This will give the harder contrast you request, at the scanning stage -- but to get this in the negative, you would need to give extended development. Most labs charge extra for this, because they can't batch your film in with other rolls of the same film type, but instead must handle it more individually -- but anywhere that processes B&W film should be able to give a one stop push. You just have to request it (and you may have to ask them how to request a push process).
You would then set your meter to 800, or for auto exposure cameras dial in "-1" exposure adjustment, shoot normally, and process with the "Push +1" option.
Here's the frame challenge answer (https://meta.stackexchange.com/questions/66377/what-is-the-xy-problem)
You want increased contrast in the end result...this doesn't mean that you need increased contrast in the negative.
The negative is simply a means to an end and it should give you the most detail possible so that you have the most amounts of "ends" available to you.
You can always increase contrast to the point that you lose shadow detail or highlight detail in the final print...but you cannot get those details back in the final if you've killed them in the negative.
Your negative should give you the best possible base from which to work. For most films, this is at or just slightly below box speed and developed normally. Since you're scanning, get the highest quality scan that you can, milking as much detail out of the negative as possible.
Now that you have this highly detailed digital file from which to work, we can begin applying post production methods to get the final image looking as you intended.
Seems to me you need to stop messing with your film and development and start asking about post-production methods. I think that you have a misunderstanding about post pro as it applies to scanned images. The vast array of tools that you'd use to build the final print in a darkroom are available to you in an image editor and can be applied to a scanned image.
