Oversampling Question - DPChallenge Forums

Canon EF 16-35mm f/2.8L USM III

08/08/2003 06:54:37 PM · #1

I am grateful to the administrators when they tell me one of my prints has been oversampled, but I can't tell when it has as I look at the image in Photoshop. In John's tutorial, it suggests that as long as you don't resample more than twice the original size, it should be okay. I know this is a general guideline, and I try to stay under that, but I'm still oversampling some of my images.

I figure I must be doing something wrong--perhaps one of these:

1. My Photoshop techniques suck, and what is seen as oversampling is actually just bad skill at Photoshop, leaving lots of grain and other digital particles floating around.

2. I am making mistakes while resampling. Here is my technique:

a. I use the crop tool, set at the desired level (say 10 in by 8 in) and crop the image.

b. in Image Size..., the size is usually 10 x 8 with a dpi of 240, if I crop at the borders of the image.

c. I resample up by 5 percent until I get to 405 dpi (I have created a Photoshop action to do this). If I don't crop to the borders, I won't go all the way to 405, but will end up in the 300s, being careful to never double my dpi (so an image beginning with 186 dpi will never be resampled over 360 dpi).

Suggestions? Does the crop tool work in (a) as I think it does?

Thanks,

David

Message edited by author 2003-08-08 18:55:01.

shutterfly

Canon EOS-5D Mark III

08/08/2003 07:04:45 PM · #2

I think there was just a thread where Drew said not to resample higher than 150 or so. I try to stay around 200. I think 405 and above would be way to much.

bod

08/08/2003 07:06:48 PM · #3

I think you're just going too high. I don't think I've ever managed to double the size of a file with reasonable results. If you're aiming for 20x16 prints then just up your 10x8 to 300dpi - this will allow you to be reviewed for the 20x16 @ 150dpi which is plenty for a high quality print.

wewillexplore

Canon EOS-1D Mark II

Canon EF 70-200mm f/2.8L IS USM

08/08/2003 07:47:55 PM · #4

If there's a Mac version of Extensis's program for PS, GET IT. Extensis is great!!!!! You can (CAN, not would like to) resample like 400% with no real loss. It's a great program.

(And yes, Drew said try not to go much above 150 dpi.)

M

Canon EF 70-200mm f/2.8L IS USM

08/08/2003 07:49:42 PM · #5

Originally posted by shutterfly:

I think there was just a thread where Drew said not to resample higher than 150 or so. I try to stay around 200. I think 405 and above would be way to much.

If I set the crop tool to 20 x 16, then the dpi ends up being 120 after cropping, and resampling to 200 is the same as resampling to 400 if I crop at 10 x 8. Does that make sense? So I'm still confused. However, if I should just to to 300 (from 240) that isn't so drastic a resample, and will that still make a decent larger pic?

pitsaman

Canon EOS-30D

Canon EF 50mm f/1.8 II

08/08/2003 07:58:06 PM · #6

Photo from your camera comes out about 2500X1950 at 72 dpi.
That is about 15X12 inches at 150 dpi!
Before you resample it higher crop it to 1:1.25 or 1:1.5 depends how you want it and do unsharp mask 1.75 at 60%.After that resize it to 16X20 or 20X30 inches and then apply BLUR/Soften filter to kill the grainy noise (once or twice depends how much grain you see) and you got it!

wewillexplore

Canon EOS-1D Mark II

08/08/2003 08:01:46 PM · #7

Originally posted by dsidwell:

Originally posted by shutterfly:
I think there was just a thread where Drew said not to resample higher than 150 or so. I try to stay around 200. I think 405 and above would be way to much.

If I set the crop tool to 20 x 16, then the dpi ends up being 120 after cropping, and resampling to 200 is the same as resampling to 400 if I crop at 10 x 8. Does that make sense? So I'm still confused. However, if I should just to to 300 (from 240) that isn't so drastic a resample, and will that still make a decent larger pic?

I make everything 300dpi at half the size I want to print it. Ex: 16x20 images on my prints are actually 8x10s at 300dpi, so yes. If you're asking what I think you're asking, that's correct.

pitsaman

Canon EOS-30D

Canon EF 50mm f/1.8 II

08/08/2003 08:06:11 PM · #8

quote]

I make everything 300dpi at half the size I want to print it. Ex: 16x20 images on my prints are actually 8x10s at 300dpi, so yes. If you're asking what I think you're asking, that's correct.[/quote]

16x20 at 150 is same as 8x10 at 300 you math wiz..

wewillexplore

Canon EOS-1D Mark II

Canon EF 70-200mm f/2.8L IS USM

08/08/2003 08:07:12 PM · #9

Erm, that's what I said. lol

I was saying David only needs to go to 150 at the size he wants or 300 at half the size...Einstein.
;)

M

kavamama

Panasonic DMC-FZ10

08/08/2003 08:34:52 PM · #10

Originally posted by mavrik:

If there's a Mac version of Extensis's program for PS, GET IT. Extensis is great!!!!! You can (CAN, not would like to) resample like 400% with no real loss. It's a great program.
(And yes, Drew said try not to go much above 150 dpi.)M

There IS a mac version and they've got a 30-day demo! for Extensis Smart Pixel

I took an 1170x1149 at 72dpi photo, resampled it to an 18x24 poster at 200dpi with NO DISCERNABLE LOSS. Its a lot more user friendly than Genuine Fractals, too. Try the demo, but be forwarned, you're going to buy the program or really wish you had.

pitsaman

Canon EOS-30D

Canon EF 50mm f/1.8 II

08/08/2003 08:40:47 PM · #11

Originally posted by kavamama:

Originally posted by mavrik:
If there's a Mac version of Extensis's program for PS, GET IT. Extensis is great!!!!! You can (CAN, not would like to) resample like 400% with no real loss. It's a great program.
(And yes, Drew said try not to go much above 150 dpi.)M

There IS a mac version and they've got a 30-day demo! for Extensis Smart Pixel

I took an 1170x1149 at 72dpi photo, resampled it to an 18x24 poster at 200dpi with NO DISCERNABLE LOSS. Its a lot more user friendly than Genuine Fractals, too. Try the demo, but be forwarned, you're going to buy the program or really wish you had.

Can it resample body parts too?
:-)
18X24 inches wow, poster it

Message edited by author 2003-08-08 20:53:08.

kavamama

Panasonic DMC-FZ10

08/08/2003 08:51:17 PM · #12

Originally posted by pitsaman:

Originally posted by kavamama:
Originally posted by mavrik:
If there's a Mac version of Extensis's program for PS, GET IT. Extensis is great!!!!! You can (CAN, not would like to) resample like 400% with no real loss. It's a great program.
(And yes, Drew said try not to go much above 150 dpi.)M

There IS a mac version and they've got a 30-day demo! for Extensis Smart Pixel

I took an 1170x1149 at 72dpi photo, resampled it to an 18x24 poster at 200dpi with NO DISCERNABLE LOSS. Its a lot more user friendly than Genuine Fractals, too. Try the demo, but be forwarned, you're going to buy the program or really wish you had.

Can it resample body parts too?
:-)
My nose is too big

Don't know about downsizing, I've only tried making things bigger! 8-) Send your nose over and I'll see what I can do....

Sony 16-50mm f/3.5-5.6 E-mount

08/08/2003 09:25:01 PM · #13

So bottom line is:

150 dpi is plenty for a 16 x 20, and 300 is plenty for an 8 x 10?

jmsetzler

Sony Alpha a6000

08/08/2003 09:35:42 PM · #14

Originally posted by dsidwell:

So bottom line is:

150 dpi is plenty for a 16 x 20, and 300 is plenty for an 8 x 10?

150 dpi is the minimum requirement.

I may be able to help you out. After you make your crop using the 16x20 ratio, go ahead and resize the image to the correct inch dimension and see what your dpi is after that resize. If it is indeed 120 dpi you should be able to get where you wanna go without much trouble if you do it in the 5% increments.

Let me know if you would like some additional help on this.. I will be glad to...

08/09/2003 12:26:34 AM · #15

So what would be reasonable for a photo starting out at 240 dpi? I have usually gone to 400 or so, which not quite doubles it.

And: can lousy Photoshopping be responsible for making it appear oversampled?

Thanks for the helpful responses, by the way!