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09-28-2007, 10:17 AM   #1
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Megapixels and cropping

How much cropping can really be done even with a 10MP camera for printing purposes.

For simplicity, take a 9MP camera and say the frame is 3x3, and even if the image of interest covers one third of the length and width of the camera frame, and is cropped to fill the frame, the megapixel would 1x1=1 MP, ...not suitable for printing.

Cropping in a linear dimension results in an exponential loss of image quality limiting the extent of allowable cropping.

Is this right?


Last edited by pcarfan; 09-28-2007 at 10:43 AM.
09-28-2007, 10:40 AM   #2
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You need to take into account print size too.

A 1 Megapixel image is fine if you're going to print a 4x5 or 4x6 at 240 ppi. I tipically prep prints for 300 ppi, so I could do 3x4 prints out of that 1 MP file without any noticeable degradation.
09-28-2007, 10:50 AM   #3
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QuoteOriginally posted by Frogroast Quote
You need to take into account print size too.

A 1 Megapixel image is fine if you're going to print a 4x5 or 4x6 at 240 ppi. I tipically prep prints for 300 ppi, so I could do 3x4 prints out of that 1 MP file without any noticeable degradation.
That is good to know, I threw in some of the images (6 fitted in a 11x9 book) to see how they look. The winkflash says it's not even suitable for 4x6's, I guess I could do 3x4.

This makes me wonder how limited one would be in using primes for landscape. At times there is no physical space to move, and to frame a landscape with a fixed focal length does'nt allow for much freedom in composition, as cropping is VERY limited for big prints. I think the ability to crop with higher mp cameras is frankly overblown. I am new to this, and it was quite a revelation when by CS2 bridge showed the crop image to be 1MP. Now, I am not too sure whether given a choice that I'll choose a 10MP camera with higher noise over a 8mp with lesser noise.
09-28-2007, 10:59 AM   #4
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In general, I'd think you'd want to crop as little as possible, hence 'getting the framing right' when shooting it. However, it's always possible to be a little off. I use a zoom right now (17-70) when shooting landscapes, but I could easily replace that with a few primes, as most of my shooting tends to be in 17/50/70 lengths. I crop about 5% on average.

Now, I print 11x17 on an Epson 2400 in b&w. My final print PPI varies based on my crops, and I have yet to notice a real difference between 200ppi and 240ppi (native res from the K10D). Even under a loupe, they still are hardly noticeable, and if someone's taking a loupe to an 11x17 print, well, perhaps they're not my target market anyhow =)

If you're cropping a 1MP section out of an 8MP or 10MP pic, I'd say you probably chose the wrong lens, or just doing an 'emergency' salvage.

Don't forget that software like CS2/CS3 and Genuine Fractals can do an excellent job of re-sampling an image so that you can still get your higher PPI's after a crop.

!c

09-28-2007, 12:08 PM   #5
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QuoteOriginally posted by shutterdrone Quote
In general, I'd think you'd want to crop as little as possible, hence 'getting the framing right' when shooting it. However, it's always possible to be a little off. I use a zoom right now (17-70) when shooting landscapes, but I could easily replace that with a few primes, as most of my shooting tends to be in 17/50/70 lengths. I crop about 5% on average.

Now, I print 11x17 on an Epson 2400 in b&w. My final print PPI varies based on my crops, and I have yet to notice a real difference between 200ppi and 240ppi (native res from the K10D). Even under a loupe, they still are hardly noticeable, and if someone's taking a loupe to an 11x17 print, well, perhaps they're not my target market anyhow =)

If you're cropping a 1MP section out of an 8MP or 10MP pic, I'd say you probably chose the wrong lens, or just doing an 'emergency' salvage.

Don't forget that software like CS2/CS3 and Genuine Fractals can do an excellent job of re-sampling an image so that you can still get your higher PPI's after a crop.

!c
I am new to all this, talking about prime for landscape etc. are me just thinking out loud.

The 1mp crop was indeed the wrong lens for the occasion. Max 250mm even on the 1.5 crop did not help for this airshow. But, I did some salvaging and here is one example of what I did....(https://www.pentaxforums.com/forums/post-your-photos/12543-composite-image.html ).

Good point about the fractals, and keeping dpi constant in resizing.

The reason for the thread frankly is me having a different vision of MP and cropping.

Last edited by pcarfan; 09-28-2007 at 09:49 PM.
09-28-2007, 09:15 PM   #6
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To get only a 1Mp image from a 10Mp would be a very severe crop -
although obviously this is not improbable as one could see some small detail area that needed "enlarging" or cropping.

Most of the time my most severe crops tend to be getting a vertical/portrait orientation crop from a horizontal/landscape shot.

For the 10Mp K10D - 3872 x 2592 pixels - a vertical/portrait crop would be 2592 x 1728 pixels (staying with the 3:2 aspect ratio) - this is close to ~5Mp

For the 6Mp K100D (& Super) - 3008 x 2000 pixels - vertical/portrait crop = 2000 x 1333 pixels (3:2 aspect ratio) - this is close to ~3Mp

10Mp K10D vertical crop (2592x 1728) -

300ppi = ~9" x 6" (full uncropped frame =~13" x 9")
200ppi = ~13" x 9"
150ppi = ~18" x 12"

6Mp K100D (& Super) vertical crop (2000 x 1333)

300ppi = ~7" x 4.5" (full uncropped frame = ~10"x 7")
200ppi = ~10"x 7"
150ppi = ~14"x 9"

Although 150ppi/dpi "sounds" horrible -
one has to take into account the viewing distance
a 18"x 12" from the K10D or even a 14" x 9" from the K100D probably would not be held in the hand - but on the wall in a frame - which means normally they are not subject to close nose-to-paper scrutiny -
probably in most cases both the cropped prints at those respective sizes would be very acceptable.

Below is something I wrote previously -

300ppi/dpi has long been held as the critical quality standard for prints -
although only a few years ago 200ppi/dpi had been touted as good quality (eg: "Popular Photography" still quotes this figure),
and I have used as low as about 160 ppi/dpi to produce many 10x8 that are closely scrutinized -
so sometimes it depends on the subject details too.

So taking that 300ppi/dpi as a critical "standard" -
one can then derive by the largest print one normally produces -

6"x4" = 1800x1200 =close enough to be ~2Mp
7"x5" = 2100x1500 = ~3Mp
10"x6.6" = 3008x2000 = 6Mp of K100D
10"x8" = 3000x2400 = ~7Mp
13"x8.6" = 3872 x 2592 = 10Mp of K10D


Let's go to the other extreme of 160dpi/ppi -

6"x4" = 960x640 = ~0.6Mp
7"x5" = 1120x800 = ~1Mp
10"x8" = 1600x1280 = ~2Mp
16"x12" = 2560x1920 = ~5Mp
20"x16" = 3200x2560 = ~7Mp

or the largest "acceptable print" (using 160ppi/dpi) from -

2Mp (1600x1200) = ~10"x8"
3Mp (2048x1536) = ~13"x10"
5Mp (2592x1944) = ~16"x12"
6Mp (3008x2000) = ~19"x13" for K100D
7Mp (3072x2304) = ~20"x16"
10Mp (3872x2592) = ~24"x16" for K10D

The beauty of larger prints - larger than 10x8 - is that they are normally not held for viewing and not usually subject to "nose to paper" scrutiny - they are normally hung on walls in frames.....
so the lowly 150-160ppi/dpi becomes more than acceptable.

For critical work or smaller prints (say 7"x5") I would still tend to use 300ppi/dpi - but 10"x8" or larger one could drop the ppi/dpi.

Using the previous "standard" for quality of 200ppi/dpi - we get these -

6"x4" = 1200x800 = ~1Mp
7"x5" = 1400x1000 = ~<2Mp
10"x8" = 2000x1600 = ~3Mp
12"x10" = 2400x2000 = ~5Mp
15"x10" = 3008x2000 = 6Mp of K100D
16"x12" = 3200x2400 = ~7Mp
19"x13" =3872x2592 = 10Mp of K10D

So generally if a camera is capable of producing 10"x8" prints at 300ppi/dpi -
which the K100D (3008x2000) can do - strictly speaking 10"x6.6" - as this is likely to be the biggest size that's handheld and subject to close scutiny (the 10Mp K10D can print full-frame at 300ppi to ~13"x9")-
any larger size are likely to be viewed at further distances so reguire less print pixel density - the K100D can probably get away with about 20"x13.3" and the K10D about 26"x 17" at 150ppi/dpi for most display purposes, and even larger if the subject does not have any critical fine detail.

In fact most people can get by with a mere 2Mp for 6x4 (or just 3Mp if more 10"x8" are planned) -

but for people who want to be able to produce really good quality 10"x8" that's close to publication standards - then a 6Mp to 7Mp is a good choice......

Obviously as suggested more Mp also means one can crop and use smaller areas and still get good quality - but 6-8Mp is good enough for most of my needs.
09-28-2007, 09:53 PM   #7
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Vincent, thanks for the insights. It will be very helpful when i start to consider larger prints.
09-29-2007, 06:47 AM   #8
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Hey Vincent,

Excellent information! I do have one question.

Although I do some very limited prints (for myself mostly), when I send my prints to WHCC, their specs require you to crop to 300 ppi, whether 4x6 or 24x30.

Have you had any experience with commercial printers that allow you to define your own ppi?

09-29-2007, 07:24 AM   #9
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QuoteOriginally posted by pcarfan Quote
How much cropping can really be done even with a 10MP camera for printing purposes.

For simplicity, take a 9MP camera and say the frame is 3x3, and even if the image of interest covers one third of the length and width of the camera frame, and is cropped to fill the frame, the megapixel would 1x1=1 MP, ...not suitable for printing.

Cropping in a linear dimension results in an exponential loss of image quality limiting the extent of allowable cropping.

Is this right?
What you are talking about is one ninth of the entire area of the image. (1x1 is 1, 3x3 is 9)

That is really extreme.
I would go to as far as to say it is unreasonably extreme.

For general cropping for the purpose of composition, 10mp is more than enough. If it isn't then you missed your shot.
09-29-2007, 09:49 AM   #10
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QuoteOriginally posted by Frogroast Quote
Although I do some very limited prints (for myself mostly), when I send my prints to WHCC, their specs require you to crop to 300 ppi, whether 4x6 or 24x30.

Have you had any experience with commercial printers that allow you to define your own ppi?

Yes, kind of - but in another roundabout way.

I have had many requests for my photos that specify them to be 300Dpi - without any other attributes/dimensions.

I think that is a "throwback" to the days of actual physical paper prints - where publications ask for (scans at) 300dpi.

Again notice this is without any other attributes/dimensions - which in itself is kind of "meaningless" -
however, my speculation is that most prints offered from non-professionals are usually 6"x4" - so that translates to 1800x1200 pixels (= ~2Mp).

But professionals used to work to 10"x8" prints as a sort of de-facto standard -
so at 300dpi that's 3000x2400 pixels - about 7Mp or sort of 6Mp dSLR frame -
that's why there was a big rush to dSLRs by professionals when the 6Mp dSLR started to become more commonplace.

Most printing places just accept a photo file and ask what size to print to -
some give additional advice to say whether the print size may be limited by the pixel dimensions of the photo file.

BTW - 24"x30" at 300ppi = 7200 x 9000 pixels = 64.8Mp!!! -
I don't think that's possible with consumer type digital cameras right now.....

Last edited by UnknownVT; 09-29-2007 at 10:19 AM.
09-30-2007, 02:45 PM   #11
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The largest print I have made is 20x30 inches - a landscape - from my *ist Ds. I had it printed through Costco, I live in Washington state and the lab (printed on fuji color paper - not inkjet) is in Maryland 3,000 miles away. I processed the image in Lightroom 1.1. When the picture showed up and I peeped it, you had to get within a few inches to see the image break up. From a normal viewing distance - 12+ inches away - it looks just fine.

The mounted image is in my wife's office - and it is generating nice comments. I have not printed any large images off of my K10D - yet, but I expect that they will stand up to this level of enlargement very well. This image is not cropped - I use the entire frame (hense I try to shoot FF - (FF does not mean 135 format by the way)) I take it to mean that I did not compose the image correctly if I have to crop.

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Last edited by PDL; 09-30-2007 at 02:48 PM. Reason: added in FF drivel
09-30-2007, 05:13 PM   #12
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QuoteOriginally posted by UnknownVT Quote
Yes, kind of - but in another roundabout way.

I have had many requests for my photos that specify them to be 300Dpi - without any other attributes/dimensions.

I think that is a "throwback" to the days of actual physical paper prints - where publications ask for (scans at) 300dpi.
Yeah, for WHCC they specify 300dpi and of course, using the ROES software you specify the size. I always work an image, then from the final version, I create copies cropped to the size required by the customer or what I want. That way I don't have to worry about someone or something messing around with my image

And as PDL points out, assuming you're not going to stare at a 20x30 image from 2" away, a 10 MP camera should be more than adequate for large prints.

QuoteQuote:
BTW - 24"x30" at 300ppi = 7200 x 9000 pixels = 64.8Mp!!! -
I don't think that's possible with consumer type digital cameras right now.....
Well... you can get somewhat close with the Hasselblad H3D-39, 39.0 Megapixel, on sale at B&H for about $800 per megapixel... oh yeah, plus tax
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