Film Scan Resolutions?
st33lz
Registered Users Posts: 6 Beginner grinner
I recently took some old negatives into a photo lab and asked that they be scanned so I could touch them and crop them in photoshop to get them reprinted. When I received the files I was surprised to find they were only 72dpi and only 5mb. I guess I was expecting some thing like 300dpi - what I've been told is print quality.
Should I be concerned that it wasn't scanned at a decent quality?
Thanks.
Should I be concerned that it wasn't scanned at a decent quality?
Thanks.
0
Comments
Keep in mind that your scan is really measured in pixels. DPI is only used to tell you how large the photo will display in a print or on the screen. For example, I have a photo that is 2592 x 3872 pixels. That's a 10 megapixel image. In a 300 dpi print, it would be 8.6 x 12.9 inches. In 72 dpi (i.e., on a computer display), it would 36 x 54 inches. The image is the same either way, it's only the display resolution and the display size that's changed.
You can open a photo in Photoshop and change the dpi without changing the pixel dimensions. The photo will actually be unchanged.
I should also mention that 300 dpi is typically the highest dpi you would want in a print. But depending on the viewing distance, you can get away with 250 dpi or even 200 dpi in most instances.
This is a controversial subject, but estimates of the maximum useful megapixels in a 35mm film scan range from about 6 to 14, depending on which film you used and how sharp your lenses are.
So what are the pixel dimensions of the scans they gave you? If they only gave you e.g., 3 MP, then you probably could do better to get them rescanned at higher quality. If they gave you 10 MP, then you're probably fine for your purposes.
A good lab will ask you how many dpi you want in the scan. Keeping in mind that a 35mm frame is 24 x 36mm (just under 1 x 1.5 inch), then a 2000 dpi scan will give you just under 6 MP. A 2500 dpi scan will give you about 9 MP.
If your lab seems a bit confused by this, you should go to another lab because they don't know what they're doing and they're probably using low grade equipment.
Mike
Thanks, this really helps.
The pixel dimensions are 3088 x 2048. I was hoping to get a decent 8x10 out of it - nothing huge.
The lab did give me an option, but it was sort of like - smaller size file or bigger size file...not very specific. This gives me a better idea of what questions I need to ask next time.
Thanks again.
Those dimensions will be decent enough for your purposes.
When asking about file size, they are probably referring to how much they should compress the image. More compression means less quality. I'm not positive, but Photoshop may be able to tell you how much compression they used. Next time I would ask them to provide the "best quality" and they should know what you mean.
Dgrin probably has some tutorials that will be helpful to you. Maybe one of the more experienced Dgrinners could direct you there. Any takers?
Good luck!
If these were 35mm slides (36x24 actual), then they were scanned at over 2000dpi to give you files that size.
-Scott
scwalter.smugmug.com
The math is:
2048 pixels along the short side,
divided by 8 inches,
equals 256 dots per inch at 8 inches.
That's more than good enough for an 8x10, assuming the actual image is sharp.
If you crop 100 pixels off that side of the picture, the resolution at 8 inches becomes
1948 pixels/8 inches or 243.5 dpi. Or, if you print the whole image at 4x6, it's 512 dpi because the same number of dots are smaller.