conversion MB Mo Solved

Question

Bonjour,
je dois "transformer" des images qui pèsent entre 2 et 3,5 Mo environ en images entre 48 et 200 Mo (mégaoctets). Quel est le rapport que je dois calculer
autrement dit: 48 Mo = 48 Mo
200 Mo = 200 Mo
merci bcp
louise

Configuration: Windows XP Internet Explorer 7.0

kwaio · Accepted Answer

1 Megabyte = 8 Megabits = 1 Mega Octet

Moustique44 · Answer

Good evening, 1 Byte = 1 octet = 8 bits (0 or 1) 1 Mega = 1.10 to the power of 6 = 1,000,000 1 MB (MegaByte) = 1 Mo (Mega octet)

kwaio · Answer

Just for fun:  Megabyte and not Mégabyte: it's in English ^^ On the other hand, megabyte =)

geef · Answer

Hello, 48MB = 48Mo 200 MB = 200Mo Mo and MB are the same thing.

eriiic · Answer

Hello,

I agree with geef
8 MB (with a capital B = MBytes) = 8 Mo
and I would add
8 Mb often abbreviated as 8 Mbits (here we're talking about bits in French) = 1 Mo

So it bothers me that Louise wrote 48 MB, which significantly increases the size of her images with no possible gain in quality, and even at 48 Mb (48 Mbits => 6 Mo...) it still adds weight.

Isn't it between 48 and 200 ko rather, Louise? Otherwise, I doubt the usefulness of the exercise...

Eric

kwaio · Answer

History of messing things up: Mio or Mo? MiB or MB? =D

louise · Answer

Thank you, but I still don't understand
indeed, it seems very heavy to me: my digital camera has 8 million pixels, I take "extra fine" photos in JPEG
to get from 48 to 800 MB (I've checked...) would I need professional equipment?
would recording in RAW allow me to reach those numbers?
in short, from a technical point of view, I'm not at the top...
thank you for your help and your patience
Louise

eriiic · Answer

Hello,

Your camera has 8 Megapixels (that's the sensor) and the size of your resulting jpg depends on the compression.
If you only have 'extra-fine' (which I think is already good because with 2-3 MB per photo, the compression is not very high), that's the maximum for your camera in jpg.
In raw, it will indeed be bigger because you have the raw data from the sensor without any processing. But your photos will not be directly usable (not even viewable). You will need to process them with specialized software.
Some devices allow for dual recording: in jpg (for immediate viewing and sharing) and in raw for later processing.

Eric

loise · Answer

Thank you Eric

here are exactly the requirements I must comply with:

JPEG’s saved at a high quality setting (i.e. Photoshop level 10 or above).
Alpha-numeric file names ending in .jpg.
RGB files, not single channel greyscale or CMYK.
Uncompressed file sizes of between 48MB and 200MB

should I conclude that none of my photos (maximum 6MB) will do?
thank you
louise

kwaio · Answer

With a digital reflex camera like a Canon EOS 40D, you can take photos up to 10MB, even 20, maybe, but not 200...

louise · Answer

Hello,

another question:

just to check... I saved a photo in TIFF format in Photoshop Elements and it turned into 20MB...

What is TIFF?
Has my photo lost quality going from JPEG to TIFF?
Should I always take photos in TIFF format?
Is it therefore more "heavy" and consequently better???

thanks again
louise

louise · Answer

thank you very much
I'll try to integrate that tomorrow morning when I have _ sleep
how complicated it is!!!

from now on, would I therefore have an interest in taking photos directly in TIFF? Is that possible?
In JPEG, what kind of details do we lose?
and who decides the compression rate? the camera or photoshop or picasa or ACDsee or the software on the computer...???

and what to do with:
JPEG’s saved at a high quality setting (i.e. Photoshop level 10 or above).
am I being asked for both uncompressed and JPEG which, by definition, seems to be compressed????

thank you again
louise

kwaio · Answer

In fact, they limit the size of the file when they decompress it, but you need to give them a compressed file (JPEG). Knowing that software like Photoshop allows you to limit JPEG compression ...

louise · Answer

Hello,

back on the site with just as many questions:

I saved one of my photos in bmp and here's what appeared

pixel dimension: 20.5
width: 3104 pixels
height: 2304 px

document size:
width: 109.5
height: 81.28

resolution: 72 px/inch = 28.346 px/cm

then should I choose
keep proportions
resampling: nearest
bilinear
bicubic

?????

in the end, does this photo fit within the 48 to 200 MB range?

I did try to multiply but my calculator can't handle it!!! not enough space on the screen!

thank you really for your help

Louise

louise · Answer

Hello,

new info:

the photo saved as bmp "weighs" 20.4 MB according to the measurement found in "properties"

is it possible that it is so little compared to the required standards: not even half of the minimum ...

would only a reflex camera do the job? or is it just the number of pixels of the camera that makes the difference?
thank you again

louise

louise · Answer

new info (continued)

after doing the calculations by hand, I got 61 MB for the photo that was only 20.4 in the "properties" section

?????

why this difference?

can the number of bits/color be 72 meaning the "resolution: 72 px/inch"?

otherwise, where can we find this measurement (number of bits/color)?
thank you

louise

eriiic · Answer

Good evening Louise,

I think you made a mistake in your calculations.
Your resolution: 3104x2304 = 7151616 pixels (your device takes photos of 7 Megapixels even though the sensor makes 8, it happens, nothing serious)
If you have a color depth of 24 bits (16 million colors, the most common), that gives you 3 bytes per pixel (24/8=3).
This means a file size of 7151616 * 3 = 21454848 bytes => 21454848 / 1024 / 1024 = 20.4609375 MB, that's what you read.

If you're at the maximum resolution of the device (which I think you are), you will never get more.
You can, of course, increase the size of your file by resampling, but it really offers no interest as you wouldn't gain anything in quality.
The resolution in pixels per inch is not related to the color depth. It depends on the display used; for example, 72 or 96 is good for a screen, but if you want to print it will be rather 200-400 pixels per inch depending on the desired fineness. And the more pixels per inch you have, the smaller the print will be (your photo is always 3104 pixels wide).
Now a question: Why is a minimum size imposed on you? Is it that important? Is it for a large format print or something else? Finally, if it's not indiscreet...

Eric

louise · Answer

Good evening and thank you for these explanations.
Actually, I wanted to try to offer my photos for potential sale...
How do you end up with 48 or even 200MB?
What type of device can take photos of that size?
Thank you
Louise
P.S.: I think my membership to this site that requires 4 photos of 48 to 200 MB is very compromised!!!

eriiic · Answer

Good evening,

If it's in 16 million colors, that is, color depth at 3 bytes, you divide by 3 to get the size of the sensor in Mpixels.
48 => 16 Mpixels
200 => 66 Mpixels !!??!!!

I'm not up to date on professional cameras, but even for them, that seems quite high...
There's something I'm missing here, it must be read as 48MB like 48Mbits (=6MB) and not 48 MBytes (MB), which would give a file size of 6 to 25 MB, much more reasonable. Rely on that value.
You should leave the website address; we might get another interpretation (although the info you provided at one point seemed clear about this)
Eric

louise · Answer

Hello,
This will help you find the explanation???
For me, English is fine, but the technique...

I have highlighted + bolded what seems to constitute a lead... but it doesn’t seem to appear on the copy paste... so, I’m putting first the “selected” elements; this may save you some time

Thank you so much
Louise

§ au moins 6 mégapixels. Cela donnera une taille de fichier d'au moins 17 Mo à 8 bits.
§
§ Si vous prenez des photos au format JPEG, utilisez toujours le réglage « Fin » (le moins compressé).
§
§ Avant de travailler sur des JPEGs fins, ils doivent d'abord être sauvegardés au format tiff ou un autre format sans compression, par exemple psd. Ne jamais sauver à nouveau des JPEGs au format JPEG - cela entraînera une perte permanente de données et une dégradation de la qualité d'image.
§
§ au moins 17 Mo à 8 bits.
§
§ Interpoler (agrandir) le fichier à au moins 48 Mo en utilisant un logiciel professionnel spécialisé. Nous recommandons Genuine Fractals™, bien que d'autres logiciels soient également acceptables, y compris les versions d'Adobe Photoshop 7 ou supérieures (si l'option bicubique est utilisée).

texte complet :

§ Utilisez un appareil photo de niveau professionnel avec une résolution « réelle » (non interpolée) d'au moins 6 mégapixels. Cela donnera une taille de fichier d'au moins 17 Mo à 8 bits.
§ Considérez soigneusement votre choix d'objectif. La qualité de l'objectif est tout aussi importante aujourd'hui qu'elle l'a toujours été.
§ Le choix entre le tournage en RAW, Tiff ou JPEG est une question de votre propre flux de travail. Photographiez en RAW pour un contrôle maximal en post-traitement. Si vous prenez des photos au format JPEG, utilisez toujours le réglage « Fin » (le moins compressé). Les réflex numériques professionnels modernes produisent d'excellents JPEG, qui sont visuellement indiscernables des RAW ou Tiff. Avec des appareils moins performants, il peut être nécessaire de photographier en RAW pour obtenir une qualité d'image acceptable.
§ Capturez des images avec un réglage ISO le plus bas possible.
§ Désactivez le zoom numérique dans l'appareil.
§ Avant de travailler sur des JPEGs fins, ils doivent d'abord être sauvegardés au format tiff ou un autre format sans compression, par exemple psd. Ne jamais sauver à nouveau des JPEGs au format JPEG - cela entraînera une perte permanente de données et une dégradation de la qualité d'image.
§ Les fichiers RAW doivent être vérifiés pour une exposition correcte, une dominance de couleur, etc., et toute ajustement doit être effectué à ce stade. Lors de la conversion à partir de RAW, assurez-vous que le zoom est désactivé - il est activé par défaut dans Photoshop.
§ Si nécessaire, faites pivoter l'image pour qu'elle soit « bien orientée ».
§ Ne recadrez pas vos images excessivement - après recadrage, votre fichier doit toujours faire au moins 17 Mo à 8 bits.
§ Interpolez (agrandissez) le fichier à au moins 48 Mo en utilisant un logiciel professionnel spécialisé. Nous recommandons Genuine Fractals™, bien que d'autres logiciels soient également acceptables, y compris les versions d'Adobe Photoshop 7 ou supérieures (si l'option bicubique est utilisée). N'utilisez pas d'interpolation « par étapes » ou incrémentielle. Vérifiez les paramètres par défaut de votre logiciel pour vous assurer que la mise au point est désactivée. Tous les résultats sont évalués sur leurs mérites, quelles que soient les méthodes utilisées.
§ Maintenant, ouvrez l'image à 100%, et vérifiez la contamination par la poussière sur le capteur. Cela apparaît comme des marques sombres et circulaires - particulièrement visibles dans le ciel et des zones similaires. Vérifiez soigneusement l'image agrandie à 100% et apportez les corrections nécessaires à l'aide de l'outil Clone, de l'outil Pinceau de correction ou de la technique Pinceau d'historique selon ce qui convient.

Conversion MB Mo

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