72dpi to 300dpi batch process

Graham004

Graham004

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Graham
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Lots of threads re on screen dpi & printing dpi. My question is what dpi is on the compact / SD card when the photo is taken that can be printed directly from digital commercial printers. As soon as I transfer it to a pc the dpi usually adopts 72dpi unless I use Canon zoom brower that converts it to 240dpi. As I print a lot of photos I am looking for software that is able to transfer directly from compact flash to pc then to cd at 300dpi in a batch mode without resizing or editing. Hope this makes sense.
 
dpi is not set on the card, but rather it will be a setting in the camera itself. I would be looking at your manual. While it is easy to reduce dpi and maintain image quality, it does not work the other way.
 
OK. Dots per inch (dpi) has nothing to do with the camera or the memory card. Its a printer setting. Just ignore the 72 dpi display, it's a default setting for most computers and monitors, and irrelevant.

The "size" of the images is determined by the Resolution settings in the camera, which you can change to suit yourself. It's measured in pixels/megapixels. eg: 3504 x 2336 pixels is roughly 8.7 megapixels, and so on, up to the camera's maximum resolution. You can also change the Quality setting, which maintains the same resolution but increases the compression and the number of images that will fit on the memory card. This will affect the quality of the final, printed, image but most people won't notice it in smaller prints.

There is a relationship between dpi and the physical size of the final print. Zoom Browser and other software applications often have a default, or suggested setting. You can change it in the print settings if you want to, for a particular purpose, but I normally just leave it alone.
 
So are you saying that I don't need to change the default 72dpi when printing. I shoot at the maxium megapixels & print anything from small to 12x18 but have always changed the dpi in photoshop to 300dpi.
 
Keep doing what you are doing now ;)

12x18 at 72dpi will look very pixelated.
 
Graham004 said:
So are you saying that I don't need to change the default 72dpi when printing. I shoot at the maxium megapixels & print anything from small to 12x18 but have always changed the dpi in photoshop to 300dpi.
Click to expand...

As already stated, you are confusing screen resolution with your printers dpi settings.
 
Ok Lets Clarify this, I've been in the print and Repro Industry for 20years. This is how it works, it's the same for print and scans etc.

Most 12megapixel DSLRs will give you a jpeg that is around 150cm x 100cm at 72dpi. When you shoot in Raw or Tiff you will get an image of around 36cm x 24cm at 300dpi.

BOTH IMAGES WILL PRINT THE SAME, one is low res at Large size, the other is High Res and Small size. The file size once opened in photoshop will be the same)

If you run a batch convert from 72dpi to 300dpi your up-rezzing and you will end up with an image thats 300dpi at 150cm x 100cm and 600meg, but quality will go down as the computer makes up the pixels thats not there. What you need to do is if you want 300dpi is reduce the image size as well so the file size remains the same. ie. 34meg at 72dpi = 34meg at 300dpi.

Best option if 300dpi is what you want is to switch your camera to tif or RAW files and not Jpeg.
 
This cooks my swede massively....

I understand that an image, say a 1mp will be 1000x1000 pixel so at 250dpi will be 4x4", or at 100dpi, will be 10x10". I also understand that the image stays as 1000x1000 pixels whichever of these setting is used. I also understand that to increase the size of the image AND the dpi require interpolating (resampling or whatever it's called) in software such as Photoshop. Is that about right?

So, here's my problem, and one that I hope you can help clear up;

Our repro dept. at work (we produce magazines) get the images in and instantly resizes them. My Nikon JPEGs (set to fine on my D200) come in at something like 350mm wide at 300dpi, whereas the shots taken on the Canons (10/20/30/40Ds, also set to a fine JPEG setting) come in at 72dpi and about 1500mm wide. Obviously, image 'pixel' width will probably be about the same from my D200 as it is from something like a 40D (being both around the 10.5mp mark) but the repro guys resize everything down to 300dpi and 400mm wide to account for double-page spread use and the fact that it's going out to a printers.

Here's the dilemma; is it right to scale down the canon shots from 1500mm wide to 400mm wide while at the same time, increasing the dpi from 72 to 300? And where does that leave my D200 JPEGs, which are 300dpi and 350mm wide, effectively nearer to the target size of 400mm wide and 300dpi?..

...And here's the rub though - the Canon shots do look ropey, especially those taken on the 10Ds because of the lower MP sensor, but mine, which are as close to target as possible (so nearly 'perfect') also turn out gash; they end up looking grainy, pixelated and just poor.

I've approached the head repro guy, who's been in the business for 20 years+ and he ALWAYS blames the photographer and camera and not his processes. But is he resizing correctly?

I was always under the impression that once you start adding pixels (by turning a 72dpi into a 300dpi) you encourage pixelation and poor print repro. Am I think straight or am I talking total tosh?
 
I was just thinking that I'd not seen you on here for a while!

It's a tricky one, but in your position what I would do is take control of the resizing myself and supply your images to them at 300dpi/400mm. What software are you using? I've found Genuine Fractals to be great for that (followed by Lightroom, then Photoshop).

To do the maths correctly, the Canon images are coming in at: 1500mm/59" at 72dpi so about 4248px, yours are coming in at 350mm/14 at 300dpi so 4900px, which as you say is pretty much the same (my maths and rounding are more than likely ropey).

Changing your Nikon images to 72dpi would give you a print size of 68"/1700mm still with the same pixels, so it shouldn't look any different on screen. Likewise changing the print size, allowing the resolution to also change will keep the same amount of pixels. The potential for image degradation comes when you try to change either the image size, or resolution, whilst locking the other. This will mean new pixels have to be created or some pixels lost. I always prefer to be in control of that process, so I can make sure the image looks good at the required size.

That probably made very little sense, but hope it helped a bit!
 
I've been into Repro for 20+ year myself. If the end result is Litho, then most pro's will resize to the correct size at 300dpi, easier to work with and faster to import at roughly the correct size of usage. If you put a 150cm image at 72dpi straight from a camera into a page layout programme, then you have to size it down to around 20% which is a pain, also any pre-flight software will flag up errors that the image is 72dpi. They will however print both the same though if allowed to go through the system. The problems occur and images look ropey due to this...
A4 needs 24meg (300dpi) to print OK, A3 (Double page spread) needs 48meg to print properly, most Digital Cameras only output between 24-30meg tif when set on raw, so up-rezzing and interpolation occurs when going to a double page spread, the quality issue depends on how good your Repro guy is at doing this conversion.
 
Excellent link, clears a lot up for me as well. I found that photoshop element 6import batch processes at what ever dpi you want, so all mine are now at 300dpi. I have trial copy of lightroom 2, but found importing at any dpi you want also converts raw files to jpeg. I need to look at it closer again and see if its worth purchasing. Thanks for all input and discussion.
 
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