I'm planning to take landscape photos and group portraits using 9x12 film (almost the same as 4x5") and maybe make a 30x40 cm (12x16") or a 40x50 (16x20") enlargement to frame. I have a fresh box of Fp4+ and hermetically sealed Efke PL25 in the freezer. Which film would you have used?
Fp4+ is a high quality film with probably no defects. The Efke 25 may have small defects, but the enlargements would be grain free. Even with large format like 9x12 the Fp4+ grain might start to show if enlarged this much? Grain is not a defect, but then I could as well use a 6x9 camera with Pan F+ or APX 25 (that I also have a stash of).
WHAT A QUESTION

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My answer : Friend - you have NO idea what you are playing with, you (obviously) have no idea what "resolution" is ?
So what do you need

? An enshurance against "grain" ?
There is Loyds London - be sure if you will call them - they think about you!
(they manage all kind of enshurances afaik)!
And don't get nervious - they will enshure your case - the police of Loyd's would also be not very expensive!
Seriously (from point to point) :
To me enlargements from 35mm in 30 x 40 are still OK! And I mean with color film !
Coming to the double : 40 x 60 thats the last border for tolerance (with color film) !
But this is not so with bw enlagements (special films - no Hp5 a.s.o.)
there the double is a normal border - so we have 60 x 80
[ one of my first enlagement I made in bw was in 100 x 140 (all in cm oft course)...]
This was from Ilford XP1 (c41 / bw film ) at 400 - 800 ASA

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Let me state T H E N you have grain (Loyd's London will NOT ensure that case)
But coming to format : 4,5 x 6 has around 2,9 x the squere of 35 mm!
That should be OK to your 30 x 40 enlargement with normal bw film!
But of course such statements like "should be OK" are relative - what is your intention ?
Perhaps you want to have a look from the absence of A N Y visiblle grain ? - OK.,...

?
So it has to be like a 9 x 13 / 10 x 15 print from Tmax100 - because there is indeed no grain
(also from inspection with a loupe - hart to identificate grain from this smallest formats)
13 x 18 is also without visible grain - OK!
We should double it to come quite near to 20 x 30 ( it is more necessary to double - right but never mind I am real lousy in maths and I don't want to need a calculator for the next steps)
Let us have the idea of a "near double" at 20 x 30 then you will be much good with 4,5 x 6!
(remember the squere) And with 6 x 9 there is the next format avaible to you :30 x 40 aha I soon
understand - you will indeed not want to see the smallest grain - hmm crazy !
Otherwise Loyd London has to pay the sum of 1.000.000 because you have an ensurance-police for that case

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Ensure friend - there is no grain ! There is no grain with Tmaxx 100!
What you are shooting (Fp4 / efke 25)! In 9x12 !
Well that should be good for a double of your format : 40 x 60 without the smallest grain
- I swear - just belive me

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What you can make with your Fp4 - it is a film not from finest grain?
I would recomand a box speed ISO 50 and development with Perceptol!
The same I would use with your efke 25 !! Yes realy (this is no joke

)!
So you come with efke at box speed 12 to the next format : 60 x 80



- without visible grain! Try perceptol and have a look what will happen to grain of ISO25 films!
Coming to tonals - of course tonals will suffer from that pull! But not extreme!
And - hope I understand you correct : Your concern is just in regard to grain / format not so much
in general?
So what I would recomand : Fp4 or efke25 use both films and compare = both are best to 9x12!
with regards
