ppi?

That's a ridiculous request, to shoot at 72 ppi. PPI is ONLY relevant when PRINTING as ppi determines the resolution of the printed image at any given dimension.

Digital cameras don't shoot at any ppi; they shoot at 'x' pixels by 'y' pixels (as determined by the megapixel size of your camera's files).

mustaphapashu said:

That's a ridiculous request, to shoot at 72 ppi. PPI is ONLY relevant when PRINTING as ppi determines the resolution of the printed image at any given dimension.

Digital cameras don't shoot at any ppi; they shoot at 'x' pixels by 'y' pixels (as determined by the megapixel size of your camera's files).

Click to expand...

PPI is also relevant when displaying on computer. However, in that case, the size would also need to be changed.

Don said:

I have a d800e and need to shoot tomorrow at a horse trials with a bunch of Canon guys. We will be shooting jpg cause there will be many thousand images. The Canon guys ask me to shoot at 72 ppi so the post will be faster.

That is 72 ppi at around 70 something inches. My question is how do I set that in camera? I know how to open that file and change it in Camera Raw to 72 but I can not find any where to set it in camera. They will be downloading the files at the show and it is a no brainer to change from 300 to 72 in post but can that be avoided and done in camera as they are shot?

Thanks

Don

Click to expand...

Yeah dpi/ppi only matters for printing.

I don't know if you can change the default dpi setting in-camera. Certainly, manufacturers could program camera firmware to make such changes possible, but I've never noticed any camera let you do this.

It is very easy to adjust dpi/ppi in Photoshop or GIMP, etc.

In Photoshop you go Image->Image Size in the menu.


In GIMP you go Image->Scale image / Image->Print Size

I like to think in terms of pixels -- how many pixels height and width.

If all you do is change dpi, the amount of pixels remains the same.

If you add pixels it's called upsampling. (The pixels are added via algorithm; the added pixels are "guessed" at and thus the added pixels tend to not look very good.)

If you remove pixels it's called downsampling. (Pixels are removed via algorthim. The end result is a smaller image with fewer pixels. But the image will still look very good. The image may need a bit of sharpening applied, as downsampling typically softens the image a little bit.)

You don't need to mess with DPI for display on a computer screen. Typically, an image will display 1:1 on the screen, regardless of what the dpi is set to.

For example, if you have a 1,000x1,000 pixel image which happens to be set at 72 dpi, and you have a second image that's also 1,000x1,000 pixels but set to 300 dpi, and open both in a browser ... they'll be the same size on the screen.

If you have a 8,000x8,000 pixel image, that's too many pixels for the screen (regardless of dpi). So then either the image will be scaled down to a size that will fit in the screen, or the image will be cropped so that you can only see a portion of the image.

Either they're pulling your leg or they don't know what they're talking about. You just never know with Canon shooters.

Well, he told you to drive with 50mph. But not how long or how far you should drive.
Just telling you the ppi is a wortless information.

But if you assume he means an 8x10 at 72ppi - that would make sense.

To reduce the file size and speed up processing, you can change the resolution to M or S size...

Don said:

I have a d800e and need to shoot tomorrow at a horse trials with a bunch of Canon guys. We will be shooting jpg cause there will be many thousand images. The Canon guys ask me to shoot at 72 ppi so the post will be faster.

That is 72 ppi at around 70 something inches. My question is how do I set that in camera? I know how to open that file and change it in Camera Raw to 72 but I can not find any where to set it in camera. They will be downloading the files at the show and it is a no brainer to change from 300 to 72 in post but can that be avoided and done in camera as they are shot?

Thanks

Don

Click to expand...

There is no such thing as shooting at 72 ppi.

If you want to project or display an image at 70 inches wide at 72 ppi, then you need 72x70 or 5040 pixels in width. On my D800, shooting full frame, medium sized jpegs are 5520 x 3680 pixels. Assuming it's the same for the E (see your manual, Image Size), that would be the optimal setting for download and display without cropping or resizing.

The only time to actually set ppi is when printing, to tell the printer what resolution to print at. When projecting or displaying on video screens the display ppi is whatever it is, and ppi settings stored in the metadata are meaningless with no effect on the display.

You would be amazed how often people throw out that spec without knowing what it means. I hear stuff like "we need that at least 2000 x 2000 px at 300 dpi." I tell the client you have plenty of resolution there, don't worry.

"But how do we change the dpi?"

It doesn't f'n matter.

Ppi/dpi only makes sense when you have a fixed physical size to your image - say with print. So a printer may tell you that they need something at 8 x 10 inches at 300 dpi. However they can skip all the mumbo jumbo and just say they need something at least 2400 x 3000 pixels. Way easier.

j_photo said:

Don said:

I have a d800e and need to shoot tomorrow at a horse trials with a bunch of Canon guys. We will be shooting jpg cause there will be many thousand images. The Canon guys ask me to shoot at 72 ppi so the post will be faster.

That is 72 ppi at around 70 something inches. My question is how do I set that in camera? I know how to open that file and change it in Camera Raw to 72 but I can not find any where to set it in camera. They will be downloading the files at the show and it is a no brainer to change from 300 to 72 in post but can that be avoided and done in camera as they are shot?

Thanks

Don

Click to expand...

There is no such thing as shooting at 72 ppi.

If you want to project or display an image at 70 inches wide at 72 ppi, then you need 72x70 or 5040 pixels in width. On my D800, shooting full frame, medium sized jpegs are 5520 x 3680 pixels. Assuming it's the same for the E (see your manual, Image Size), that would be the optimal setting for download and display without cropping or resizing.

The only time to actually set ppi is when printing, to tell the printer what resolution to print at. When projecting or displaying on video screens the display ppi is whatever it is, and ppi settings stored in the metadata are meaningless with no effect on the display.

Click to expand...

I would love to hear how the Canon guys are setting their cameras to 72 ppi. It would be most amusing. I believe j_photo gives the correct answer in how you would come close to 72 PPI at 70 inches.

HOWEVER...

Something isn't right here. It sounds like these images are going to be uploaded and then displayed at 70 inches using a projector or 70" TV screen. Either way you will only get the resolution of the display device. A 72 PPI at 70 inch image equates to just under 17 MP. Assuming an HD device you only need a 2 MP image. Even if they have a 4K device you only need an 8 MP image. So uploading medium sized JPEG is still overkill. All you really need is 36 PPI image at 70 inches, or a small size JPEG.

All very interesting stuff. Does anybody know how jpeg images get down scaled when they are display on a computer monitor?

thejohnnerparty said:

All very interesting stuff. Does anybody know how jpeg images get down scaled when they are display on a computer monitor?

Click to expand...

Some sort of algorithm.

For example (and this is probably not really how it works) imagine making a 1,000 pixel-wide image half its size by removing every other pixel for a 500 pixel-wide image.

E.g.

this series of letters represents horizontal resolution of 1,000 pixels lets say:

xcxcxcxc

take out every other "pixel" and you get half the size:

xxxx

(then also do the same for vertical resolution, of course)

thejohnnerparty said:

All very interesting stuff. Does anybody know how jpeg images get down scaled when they are display on a computer monitor?

Click to expand...

It depends, usually by software (the one rendering the image, could be an application like LightRoom, Preview or even the Operating System). Sometimes through hardware (for example a fixed resolution projector with a built-in scaler in silicone being feed with higher or lower resolution than native).

Oh yes, maybe I misunderstood the question, it is off course made using an algorithm (implemented by hardware, software or in combination), e.g:

http://en.wikipedia.org/wiki/Image_scaling

http://www.cambridgeincolour.com/tutorials/image-interpolation.htm

Thanks everyone!! Been a little busy today. Ok here's the deal, sorry for any and all confusion about this question. I am a large format printer I understand dpi/ppi I happen to use dpi cause I come from an old time graphics background (no computers). Life is so easy now!!

If anyone here ever opened a Canon file to print or whatever the file is displayed as 72 dpi @ 70 or so inches depending on the chip size. Nikon on the other hand displays a file @ 300 dpi @ 12x18 or some such.Too tired to get the numbers exactly right. The files are the same size just handled differently. They (the Canon guys) ask me if I could change my images to open as a 72 dpi jpg so they would not have to take an extra step to change mine from 300 dpi for post.

Well they got 300 dpi jogs , 3000 of them today. Jpeg shooting is most disagreeable to my 800e but they got what they ask for, almost. Must say that new 80-400 was lovely.Thank God for monopods.

Thanks for all the responses

Don

altair8800 said:

mustaphapashu said:

That's a ridiculous request, to shoot at 72 ppi. PPI is ONLY relevant when PRINTING as ppi determines the resolution of the printed image at any given dimension.

Digital cameras don't shoot at any ppi; they shoot at 'x' pixels by 'y' pixels (as determined by the megapixel size of your camera's files).

Click to expand...

PPI is also relevant when displaying on computer. However, in that case, the size would also need to be changed.

Click to expand...

Only if you're typing text on a photo / using it for some graphic design project.

thejohnnerparty said:

All very interesting stuff. Does anybody know how jpeg images get down scaled when they are display on a computer monitor?

Click to expand...

They don't, unless you downscale them.

Don said:

If anyone here ever opened a Canon file to print or whatever the file is displayed as 72 dpi @ 70 or so inches depending on the chip size. Nikon on the other hand displays a file @ 300 dpi @ 12x18 or some such.Too tired to get the numbers exactly right. The files are the same size just handled differently. They (the Canon guys) ask me if I could change my images to open as a 72 dpi jpg so they would not have to take an extra step to change mine from 300 dpi for post.

Click to expand...

Interesting. AFAIK this can't be changed in camera (with Nikon, at least).