Confuse with image size for printing


SamPaul

New Member
Sep 5, 2007
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#1
Can someone please enlighten me?

Let said I've a photo with the following size:





Can I still print a sharp image in a size 72" x 48" by simply changing the resolution to 300. Like this:






Or I can only print an image of 17.28" (5184/300) x 11.52" (3456/300) with this picture?

Kind of a little confused....:confused:
 

hugolim

New Member
Jun 30, 2008
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#2
The typical dot per inch for printing is 300 pixels per inch. On how large you can print, it's all up to the resolution of your photo. by simplying switching it to 300pixels/inch in your second screenshot, you have dramatically increased the resolution to 21600x14400 which is not correct.

and you are right! with 5184x3456, the theratical printing size at 300dpi is 17.28 x 11.52 inches.
 

SamPaul

New Member
Sep 5, 2007
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#3
The typical dot per inch for printing is 300 pixels per inch. On how large you can print, it's all up to the resolution of your photo. by simplying switching it to 300pixels/inch in your second screenshot, you have dramatically increased the resolution to 21600x14400 which is not correct.

and you are right! with 5184x3456, the theratical printing size at 300dpi is 17.28 x 11.52 inches.
Got it! Thank you very much...:thumbsup:
 

Michael

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Apr 5, 2005
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www.pbase.com
#4
The typical dot per inch for printing is 300 pixels per inch. On how large you can print, it's all up to the resolution of your photo. by simplying switching it to 300pixels/inch in your second screenshot, you have dramatically increased the resolution to 21600x14400 which is not correct.

and you are right! with 5184x3456, the theratical printing size at 300dpi is 17.28 x 11.52 inches.
if you do the increase in pixels then photoshop will have to create those pixels by interpolating the values from pixels around the new pixels.. close up this will give you soft picture but then a 72 inch print is not look at from 10cm but from 2-3m at least... so yes you could
 

ortega

Moderator
Staff member
Nov 2, 2004
23,694
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Singapore, Singapore, Singapor
#5
not entirely true, if you want to be kiasu then stick to the 300 dpi rule

just fyi bus ads have a minimum resolution spec of 50 dpi
 

johnlim

New Member
Feb 26, 2004
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#6
I think the bicubic interpolation has been greatly improved by Adobe, so it isn't a problem if you want to increase the size to 100-200% . Do a search in the webs and you will know it can easily be done.
 

jopel

Senior Member
Dec 21, 2004
1,175
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#7
not entirely true, if you want to be kiasu then stick to the 300 dpi rule

just fyi bus ads have a minimum resolution spec of 50 dpi
btw when I used my reading glasses I can count the pixels on the bus ads, amazing resolution. :bsmilie:
 

vengels

Senior Member
Apr 30, 2007
1,719
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#8
sorry to hijack this thread..

i am using a D90..
if i want to print a 8R picture or 4R picture..

do i have to adjust any of the image size?or can i just print?..
 

catchlights

Moderator
Staff member
Sep 27, 2004
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Punggol, Singapore
www.foto-u.com
#9
sorry to hijack this thread..

i am using a D90..
if i want to print a 8R picture or 4R picture..

do i have to adjust any of the image size?or can i just print?..
the aspect ratio of D90 is 2:3, same as 4R, you can make print direct from the image file, will not have any part of image being crop away.

the aspect ratio of 8R print is 4:5, some part of the image will be crop off if is "Fill in", or showing two white borders if is "Fit in".

you can crop it yourself using softcopy,
or leave it to the lab people to crop it for you, but bear in mind than you can't complain if the cropping is not to your liking.
 

2evans

New Member
Nov 8, 2007
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#10
I think the bicubic interpolation has been greatly improved by Adobe, so it isn't a problem if you want to increase the size to 100-200% . Do a search in the webs and you will know it can easily be done.
Would you simply up the size immediately to 100-200% or perform incremental increases, i.e. 10% at a time?
 

vengels

Senior Member
Apr 30, 2007
1,719
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#11
the aspect ratio of D90 is 2:3, same as 4R, you can make print direct from the image file, will not have any part of image being crop away.

the aspect ratio of 8R print is 4:5, some part of the image will be crop off if is "Fill in", or showing two white borders if is "Fit in".

you can crop it yourself using softcopy,
or leave it to the lab people to crop it for you, but bear in mind than you can't complain if the cropping is not to your liking.
oic..

thank you so much..
 

theRBK

Senior Member
May 16, 2005
2,048
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#12
typically for "hands-length" viewing distance "photo-quality" prints, sharp 180ppi images are good enough for print... taking the example above, a sharp 5184x3456 image would probably be ok for a print up to 28.8"x19.2"... although, do people view such a large image so close-up? it's possible I guess...

but as others have pointed out, pixel density requirements also depend on the viewing distance... for viewing at a couple of meters away, such as large posters and the like, 50-75ppi is perfectly possible as well... just don't expect to see sharpness and resolution standing close...

as for expanding in Photoshop, conventional wisdom seems to be towards using "Bicubic Smoother" to expand in one shot up to about 400% for sharp images and then using your favourite means to sharpen the resultant image... YMMV...
 

johnlim

New Member
Feb 26, 2004
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#14
Would you simply up the size immediately to 100-200% or perform incremental increases, i.e. 10% at a time?
That used to be the way in the past, but I have read books which say that it is not necessary now(the software has improved alot since then); Also, using incremental method will result in far greater file size than the 1 time method. , just increase to the amount you want.

It is said that bicubic smoother is good if it is a portrait for upsizing where there there is less details. Bicubic sharpening is good for landscape where more details need sharpening...., also for downsizing.... The other bicubic option is somewhere in between; A little bit of sharpening is applied by the program during the upsizing.

NO harm trying on each option to see which one works better.
 

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theRBK

Senior Member
May 16, 2005
2,048
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#16
Bus ads in Singapore is 150dpi minimum.:cool:
that may be what they claim, but they are just wasting everyone's time cause:

a) they don't need the resolution because people view it from a distance and can't see greater detail anyway, ;p

b) the "so-called" "150dpi" files they get are probably mostly blown up in computer just to get to that spec, meaning the images don't have that much resolution to begin with anyway, and from what we can see on buses on the road this is evident, ;)

c) taking 13' (~4m... they should be higher but I just use a convenient figure here) as the height of a double decker, minusing the ground clearance of say 1 1/2', the image would have to be 11 1/2' high... translate that into 150ppi image size, the height would be 20700 pixels high for single full height photo images (not taking into account any cropping that might be required)... the highest res MF digital format back can't achieve that without significant up-sizing (Phase One P65+: 8984x6732; Leaf Aptus-II 10: 9288 x 6000; Hassey H4D-60: 8956x6708)... and those MF digital backs were only available in the past few years... DSLRs even more difficult to get to that size (D3X, 6048x4032)... :bsmilie:
 

theRBK

Senior Member
May 16, 2005
2,048
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#17
Bicubic sharpening is good for landscape where more details need sharpening...., also for downsizing....
using Bicubic Sharper to up-size, even for more detailed images, might not give as good a result as the sharpening applied with the up-size algorithm might reduce the amount of detail that is retained... one might get "crunchier", "sharper" looking images, but actual detail might be reduced... I would still recommend Bicubic Smoother and then doing the sharpening oneself as there would be more control over the final result... but for downsizing, yeah, it works great :)
 

johnlim

New Member
Feb 26, 2004
554
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#18
using Bicubic Sharper to up-size, even for more detailed images, might not give as good a result as the sharpening applied with the up-size algorithm might reduce the amount of detail that is retained... one might get "crunchier", "sharper" looking images, but actual detail might be reduced... I would still recommend Bicubic Smoother and then doing the sharpening oneself as there would be more control over the final result... but for downsizing, yeah, it works great :)
You must have done it well. :)

How long does it takes for the sharpening after the upsizing because the file must be huge in size.
 

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