File size surprise

[charlesp]

<p>Just when I thought I had the relationship between image file size and printable size figured out, sort of, this happened.<br>

I'm exhibiting at a trade show next month and I'm choosing images to have a graphics co. output on to vinyl, and apply to backdrop Sintra panels for my display booth. The images I will be displaying will be product shots from a supplier in the UK. He told me the images were from 1.4MB to 5MB each. I replied that they would be too small as some images will be as large as 120cm/4' in the long dimension. He assured me that they had printed from those files in Europe and had printed at 120cm x 160cm!<br>

So I hesitantly had him email my graphis co. a sample image to test and he sent a 1.4MB image. I saw a test strip today printed at approx 150cm/5' and was amazed that the image looked fine. Almost like a slightly soft focus, which actually works in this application. I can only surmise that in this application, i.e. display panels in a trade show viewed from a distance, that the sharpness I had assumed would be critical is simply not. But there was no sign of the "jaggies" I expected to see. So much for insisting that the supplier send 200MB files to an FTP site. Any idea why this tiny file size printed to a large size so well?</p>

 

[acedigital]

<p>The endless discussions about needing more megapixels and larger output files is largely overstated.<br>

True that larger files will give more detail, but I have had a pro lab print small files from a 3.1MP Sony camera as large as 36x24 inches and they looked fine. With interpolation software etc if the lab knows what they are doing, large prints look fine from a few feet away in many cases.</p>

 

[mark_sirota1]

<p>Actual file size (the number of bytes as the file is stored on the disk) is irrelevant. What matters is the number of pixels, and the resolution (pixels per inch or pixels per centimeter).</p>

<p>Unfortunately, Photoshop has confused the world by displaying a complex product (number of pixels times bytes per pixel) as "file size", even though it has little relation to the actual file size. The world needs to get away from this confusing notion.</p>

[patricklavoie]

<p>Agree with Mark that file size is irrelevant, as if you talk about a jpeg when close can be 2meg, and open 50meg.. and with this 2/50megs file you can get a vast array of format with quality...</p>

<p>But it is close to imposible to get something that look good if your jpeg is 2meg when open in Ps.. that will mean it is a 4x6inch at like 150ppi, and to get a decent poster size you will need to interpolated it at 800% or so.. Ok for most amateur, but definatly not for a pro looking for a pin sharp image that look good from 2inch ; )</p>

<p>Pixel x Pixel is also irrelevant in the printing / graphic design world.. what whe need is a inch size at 200-300ppi.. if pixel size was really important you would buy your paper with pixel size on the box dont you think ; ) .. but whe are still talking about 4x6, 5x7, 8x12 for a reason; this is what people know.</p>

<p>File size dotn say anything when the file is close, open it in Photoshop, have a look at the inch size and at what ppi it is, and from there you can calculate at what final print size it could be print, what ppi they need, and important data is to know at what distance you intend to show this image to people.. the closer they are, the more ppi you will need to keep the file sharp and pixel free... but then again, what you consider good and acceptable could be barely acceptable by me.. depend of our point of view and the quality whe are use to see.. i work with image from Canon Mark II to Phase One P45-65.. so im use to see skin pore and microscopic details when correctly print ; )</p>

[charlesp]

<p>I just took a look at the original 1.4 MB file provided and, looking at it at 60" x 50.014, it indicates 70 ppi.<br>

Yet when printed without up-rezzing, it looked fine for the purpose intended.</p>

 

[patricklavoie]

<p>70ppi is not a surprise for vinyl, i have seen image printed at 36ppi and they where looking not that *bad* due to the vinyl textured and the viewing distance.. so like i said, the original is 1.4meg closed, and when open in Ps it is probably another file size (irrelevant in our discusion, but just to point out that it is important to know if the file size is when the file is closed or open in Ps..)</p>