Difference in grain in the same film. Why?

[Joao]

Hello
Can someone give me an explanation for this ?
Camera Yashica 35ME, film Fomapan 100 developed , scanned and recorded in CD at the central Fujifilm lab in Lisbon, Portugal.
Some frames sorted out with obvious grain, like these two


Others from the same roll showed almost no grain, like here:

Two more things:1 - other rolls developed and scanned in the same place (Fuji Acros 100 and T Max 100) didn’t show this difference; 2- the grain is more obvious in outdoor photos (closed diaphragm) than in low light photos (open diaphragm).
Why such a difference in grain between pictures from the same roll ?
Probably my ignorance - but I would appreciate some explanation for this difference.
Regards
Joao

 

[blue4130]

It is most likely under-exposure of the negatives. What you are probably seeing is the result of the scanner trying to salvage the photo. Can you take a snap of the negative? Do the grainy shots look less or more dense than the others?

 

[Noll]

What do the negatives look like? Were they all properly exposed? My guess would be that the grainier photos were either way over or under exposed, which the scanner or scanner operator then compensated for.

 

[Dwig]

With traditional B&W films, overexposure will increase grain. The first pic in the OP's post looks to have been significantly overexposed, judging from the tonality differences between it and the 3rd.

 

[Joao]

With traditional B&W films, overexposure will increase grain. ..

. The first photo is obviously over-exposed but I did not expect such a difference . My ignorance - as I tought.
Thank you for your explanations.
Regards
Joao

 

[mfogiel]

Joao,
Grain can be affected by lots of factors, exposure in the first place and then type of developer, development time ( or even temperature), type of agitation, if you use or not the stop bath, if all baths are at constant temperature, and some other tricks too.
In your case, as said above, most likely you have over or under exposed the film, and the scanner aliasing did the rest. Ah, I forgot that the scanner aliasing and PS sharpening play a big role in the final image as well.
Bottom line: if you are passionate about B&W photography, develop and scan yourself, will be happy to give you tips on how to proceed.

 

[Joao]

Joao,
Grain can be affected by lots of factors, exposure in the first place and then type of developer, development time ( or even temperature), type of agitation, if you use or not the stop bath, if all baths are at constant temperature, and some other tricks too.
In your case, as said above, most likely you have over or under exposed the film, and the scanner aliasing did the rest. Ah, I forgot that the scanner aliasing and PS sharpening play a big role in the final image as well.
Bottom line: if you are passionate about B&W photography, develop and scan yourself, will be happy to give you tips on how to proceed.

Thank you for your remarks. I was surprised by the difference in grain in the same roll, and I have never seen such a difference related only to different exposures . I don't know the developing protocol or the scanning details - as it was done at a central Fuji Lab I presume that a minimum of quality standards were met. None of the pictures was sharpened by me, BTW.
I usually develop and scan my B&W films at home - but due to a major masonry work in my house (lots of dust !) I have all my lab equipment and most of my cameras temporarily boxed. I hope to re-start using everything again next month..
Regards
Joao