[biz-engineer]

Why not have all three (mega pixels, lens, AND optimal processing)? If one can afford it, capturing optimum number and quality of pixels opens up all sorts of options to the serious photographer.

The cost of camera systems increases exponentially to sensor size, not necessarily proportionally to perceived quality. The whole issue with digital vs film is for digital to cost of ownership is huge. It is such that only pro / commercial photog can access native medium format. Rental would be the only reasonable way of getting print material at decent cost. If it's about to make 10 prints/year, know-how is a lot cheaper than camera equipment.

For example, the appropriate viewing distance is higher for vertical prints than it is for panoramic because our angle of view is wider horizontally, it's good to have this in mind, 8256 pixels would be an overkill for a vertical poster, and more effective for a panoramic print. Panoramic landscape, how about to make 3 vertical exposures, crop each frame 4:3 and stitch => excellent quality and it cost nothing. From the prints I've done at 120 to 180 dpi, I think 300 dpi is an overkill (one need a magnifying loupe to see any dots).

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Last edited by biz-engineer; 04-01-2019 at 11:01 AM.

[PDL]

I will chime in again:

I have printed one image at 20"x30" twice with great results. One on glossy paper and one on canvas, same picture developed er Processed in two different version of Lightroom. Both have been big hits with viewers. The first one on glossy paper, hung in my wife's office for several years. The second one on canvas hangs in my bedroom, one of the first things I see each morning when I get up.

The image is of Aroaki (Mt. Cook) in New Zealand, taken in 2006 with my 6MP *ist Ds (RAW of course). If you process the image within reason the image will come out just fine.
PENTAX : PENTAX Photo Gallery artist page
Aroaki / Mount Cook 1

[emalvick]

Good thread and comments.

I've printed photos down to 150dpi to suite an older K10d photo (that was cropped) onto a large poster sized sheet of paper.

I do generally try to get the most resolution I can get for printing, but I don't fret it too much. If I am printing big, I hope to be standing back to look at the image anyway to see it.

The thing I notice most when printing large images is the quality of the lens, more than anything.

Looking back, I was most happy with the 16MP images from my K5 because they had a nice flexibility in cropping an image and still printing at a decent dpi (150 minimum). Cropping is the only reason I would hesitate to say all one needs is a 3MP or 8MP image. Cropping also allows one to overcome some lower quality lenses (those where the edges aren't good).

[biz-engineer]

The thing I notice most when printing large images is the quality of the lens, more than anything.

I agree. I realized that more megapixels on same sensor size mean blowing up lens CA. I have a large print from the K5 and 17-70, without lens correction, the first thing we see it the fringing on parts of the image with dark edges over bright background, more pixels pixels for more enlargement would make fringing even more prominent. So we are sold on more pixels (pixel shift etc) while in fact the lens / format is the limitation.

[emalvick]

I agree. I realized that more megapixels on same sensor size mean blowing up lens CA. I have a large print from the K5 and 17-70, without lens correction, the first thing we see it the fringing on parts of the image with dark edges over bright background, more pixels pixels for more enlargement would make fringing even more prominent. So we are sold on more pixels (pixel shift etc) while in fact the lens / format is the limitation.

Right, and I don't think it is just CA.

When we start dealing with a lens that is softer, we might need a higher dpi to maintain what appearance of sharpness we can get, or we put a lot more effort into sharpening in PP. But it isn't too straightforward because that need develops because we have more resolution. It is a bit of a chicken and the egg situation.

Ultimately, it's probably best not to think too hard about these things, but it is useful to be aware that we don't need 300 dpi for everything we print (despite what a printer might tell you).

[normhead]

Ultimately, it's probably best not to think too hard about these things, but it is useful to be aware that we don't need 300 dpi for everything we print (despite what a printer might tell you).

The fact that a picture might look better by some measures printed between 200-300 DPI, which is entirely debatable, doesn't mean if you have an image with a real 150 Dpi you won't enjoy it. I always figure, print what you have at the size you like. Be adventurous. It might be wasted money, but I have some great prints that have been hanging on our walls for years, that my current printer would send me a notice for, stating that they might not be acceptable. Which is really funny when we are reprinting it because we sold the original.

(125 real DPI is my bottom limit. (A 6000x400 K-3 image is approx. 27000 lw/ph, 3000 before compete extinction, so 125 DPI is actually about 63 lines per inch.)

[biz-engineer]

The fact that a picture might look better by some measures printed between 200-300 DPI

Looking at the specification of printer for large prints, more than 150 PPI on the 8bits JPEG input file fed to the printer doesn't improve the output. The key is to understand the difference between DPI and PPI..For example, if the print max DPI is 1200 DPI for large prints, it needs an 8 x 8 dot grid per pixel => 1200 / 8 = 150 PPI max. If the pixel density of the JPEG image file exceed 150 PPI, the image output get more detail at the expense of tone gradation. Understanding printer limitation tell a lot why a lot of cameras deliver 24Mp: simply because the print tech (printers) or display tech (4K displays) can't efficiently use more pixels. And oversampling the image file before sending it to the printer doesn't make any difference, it just displace the trade-off between detail and tone gradation.

[photoptimist]

The contrast and expected sharpness of the subject also factors into this. I've seen test output for 1-bit monochrome printers where a 600 dpi print was noticeably better than a 300 dpi print. The test image was text and the difference in print quality was noticeable in the sharpness of the serifs and the slightest of stair-stepping in circular letters such as "O."

Thus very high contrast scenes (e.g., spider webs, distant telephone wires, twigs on leafless trees, astrophotography) might benefit from higher-resolution printing than would scenes with smoother tonal gradations and few strong edges.

[biz-engineer]

Thus very high contrast scenes (e.g., spider webs, distant telephone wires, twigs on leafless trees, astrophotography) might benefit from higher-resolution printing than would scenes with smoother tonal gradations and few strong edges.

Yes, this makes sense.

[normhead]

When Apple cancelled idisk I lost many image files. I found one I liked somewhere and printed it, even though I could only print 72 DPI. As a 4x6 it looked fine, as good as most of my film images. A lot depends on the image and what you want it for. And as I always say, sometimes the lower res image looks better. I try and stay over 100 lw/ph, and that was a standard since forever. It's much better standard than DPI. So a K-3 at 2700 lw/ph should be good to 27 inches. A K-1 should be good to 34 incase. That's probably more detail than you're likely to see. If you're setting up a clinic to sell hi res printing equipment and cameras, I'm sure you can make case for higher resolution. I'm also pretty sure you're going to be selecting your images to make your point and discarding the images that wouldn't help.

Images like this (similar images have sold for over $1million, when a big name photographer was selling it) need good enlargement software, resolution is optional, resolution isn't what it's about.

[TonyW]

Be careful when considering visual acuity numbers they do not tell you the full story.

Conventional wisdom using the required maths finds that the average human eye (20/20) can resolve somewhere over 300 pixels per inch. But this is just to give an impression of continuos tone, it does not mean you cannot tell the dots are there merely informs you that you will not see the white space in between the dots at a certain distance.

Therefore printing at over 700 ppi can reveal detail improvement in images. I am not sure what the actual limit is but would suggest that it is certainly potentially over 3x the visual acuity figures often cited. 1200 or 1440 ppi can depending on printer and image show improvements in resolution over 600 - 720 ppi over 300- 360 ppi

The resolution key is not if the image is actually 8 bit JPEG or 16 bit TIFF but is related to what happens to the resampling of an image in the print pipeline. Send a 100 ppi image directly to the print driver will result in the image being interpolated to the print drivers requirement as declared to the OS i.e. 300 or 360 ppi spooling to a bitmap using Nearest Neighbour. Sending via a print savvy application PS, LR Qimage will use slower but better algorithms to pass the data to the printer which will not need any printer interpolation.

If you do not want to print then you can simulate what happens quite easily. Take an image with loads of detail sharp diagonal edges circles etc. Duplicate twice. Upsample the first 200% and select Nearest Neighbour. Upsample the second using Bicubic. Depending on image you should see a difference in data being sent to the printer. Bear in mind that you can only judge by actually printing which will reveal the qualities of both image and printer capability.

Stand far enough away from your print/screen then the following will become irrelevant
Native pixel count,
PPI sent to printer
DPI printer uses
Lens quality resolving power
Diffraction
Blur motion or focus
Handheld vs Tripod

I agree with the sentiment that resolution and sharpness is not what all images are about only you can decide what you require

[normhead]

In film days 100 lw/ph was considered acceptable for large prints. I'm not going to re-invent the wheel.
Upsampling to make best use of the printer is a no brainer.
The difficulty of finding printers who can print 600 or 700 dpi makes it pretty much a moot point, you're probably going to be printing at 300 or 360 DPI. Upsample accordingly.

Even if you could find a printer who can print 600-700 DPI, how much more expensive would it be? If you're selling your images double the price to you exponentially increase the price to the customer. Can you really make money doing that. If it's for yourself, is it worth taking on the additional costs?

These are of course not technical considerations. But, I hate technical information presented in a vacuum, as if that's all you have to think about.

Just a few observations from previous conversations.

[biz-engineer]

Even if you could find a printer who can print 600-700 DPI, how much more expensive would it be?

What happens is if I compare printer specs, the DPI spec decrease with print size. A4 printers can make 4500 dots per inch , but the printers that can print A2, A1, A0 can do 2400 and 1200 dots per inch max. Given that the printer recreates a pixel using many dots, at some point the larger the print, the lower the need for more pixels per inch, simply because for A2,A1,A0 print sizes, the printer won't be able to use the extra info. So, my point was, if I print a K1 image A4 and the A4 printer can resolve 4500 dpi, the A4 print will contain extremely fine details. And if I print the same K1 image onto A2 paper, it's also fine because the A2 printer max dpi is down to 1200. Big printers can't maintain the same DPI as the print gets larger, either because high DPI is more difficult to make for bigger print heads, or simply because printing A0 at 4500 would take ages and therefore not be commercially viable for the printing company.

---------- Post added 29-04-19 at 21:35 ----------

Ex. Canon Pro10 spec: print size A3+ , 4800 dpi max.
Canon Pro 1000 spec.: print size A2, 2400 x 1200 dpi max.
Canon iPF Pro 4000: 2400 x 1200 dpi. Nozzlle pitch 600 dpi x 2. ... ?
[ https://www.canon-europe.com/for_work/products/professional_print/large_form...pecifications/ ]

---------- Post added 29-04-19 at 21:55 ----------

So a K-3 at 2700 lw/ph should be good to 27 inches. A K-1 should be good to 34 incase.

Such figure is more relevant than simply pixel count, because the number of lw/ph integrate image details content from both sensor and lens.

[TonyW]

In film days I was professionaly hand producing B&W prints up to 36 foot wide (12’ max sections with max depth 52” limit of paper rolls) using an 8 x10 horizontal enlarger for other professionals exhibition work as well as our own clients. Lp/mm pretty much ignored having to sometimes duplicate a 6x6 neg up to 5x4 to get the size correct for the tthrow of the enlarger. If it looked good at a proper distance the client was happy so was our bank. The technical details irrelevant and rarely discussed unless client expectations too high e.g. a small negative enlarged and quality (grain, sharpness) to remain as if the print no larger than full plate.

I agree that it may be difficult to find print labs (non pro) prepared to take larger files 600 - 720 ppi and would not like to make comment about cost other than to say that it should not really cost more as the material cost paper and ink will be the same (well ink close enough to be irrelevant) and time to handle a larger file measured in seconds. Double the price to you for the same size print is really taking the p. In most cases 300/360 ppi quite likely to be perfectly acceptable and even if 600/720 ppi would reveal more detail it may not be important that a little IQ left behind
I have not checked lab costs for such a long time so am out of touch even in my own country.

Technical information may have to be and is often separated from aesthetic consideration. For instance how often have you seen mention of lens resolving power, diffraction etc as being of great importance as if that is all that you need to think about? Correct handling of image data from Sharpening stages through to optimal output resolutions are of equal importance if you wish to maintain these otherwise you have dropped them in the trash can.

I do agree if you are saying that these technical considerations are just a part of the image making process and need to be put into proper perspective

---------- Post added 04-29-19 at 02:21 PM ----------

What happens is if I compare printer specs, the DPI spec decrease with print size. A4 printers can make 4500 dots per inch , but the printers that can print A2, A1, A0 can do 2400 and 1200 dots per inch max. Given that the printer recreates a pixel using many dots, at some point the larger the print, the lower the need for more pixels per inch, simply because for A2,A1,A0 print sizes, the printer won't be able to use the extra info. So, my point was, if I print a K1 image A4 and the A4 printer can resolve 4500 dpi, the A4 print will contain extremely fine details. And if I print the same K1 image onto A2 paper, it's also fine because the A2 printer max dpi is down to 1200. Big printers can't maintain the same DPI as the print gets larger, either because high DPI is more difficult to make for bigger print heads, or simply because printing A0 at 4500 would take ages and therefore not be commercially viable for the printing company.

---------- Post added 29-04-19 at 21:35 ----------

Ex. Canon Pro10 spec: print size A3+ , 4800 dpi max.
Canon Pro 1000 spec.: print size A2, 2400 x 1200 dpi max.
Canon iPF Pro 4000: 2400 x 1200 dpi. Nozzlle pitch 600 dpi x 2. ... ?
[ Specifications & Features - Canon EOS M6 - Canon Europe ]

---------- Post added 29-04-19 at 21:55 ----------


Such figure is more relevant than simply pixel count, because the number of lw/ph integrate image details content from both sensor and lens.

The number of lw/ph is pretty much irrelevant to the printer and does not directly correlate to the laying down of ink. Lower or higher figures do not matter as the printer is pretty much fixed by its own limitations of 300/600/1200 ppi for Canon.

There are differences between professional level print heads and consumer, prosumer heads and the way that ink is laid down the important part in holding your image resolution is the PPI of the image not the DPI.

You have already identified that it can take many DPI to print 1 PP1.
DPI is a measure of stepper motor movement (not dot size) the most relevant being the lowest figure representing the X direction the higher figure representing the movement of paper in the Y direction

DPI is not a measure of dot size it cannot be as ink is laid down as a volume in picolitres (a trillionth of a litre). Picolitre volume may vary as the ink is thrown out of the nozzle onto the paper and it will be absorbed and spread depending on how the paper reacts when it receives ink

The nozzle pitch quoted as 600 dpi is a clue/confirmation that Canon use 600 PPI as a standard resolution figure (yes I know that they insist on putting it as DPI but…). The print head will contain a number of nozzles up to 600 in the Y direction but likely to be actually 300 with the X stepper motion controlling the minute movement to allow the recording of 600 pixels worth of image data.

You will also see that there are 18,432 nozzles (1536 nozzles x 12 colour) and a minimum ink droplet size of 4 picolitre(pl) per colour. Therefore at every point where ink is required the stepper motor can move to that point and squirt out the smallest volume of 4 picolitre but it may actually squirt out a larger volume (not disclosed by Canon) and it will also possibly overspray as the head lays down ink in multiple passes. Picking a higher DPI setting if allowed will not necessarily increase image resolution but will throw more ink at the paper and may show better densities.

Not all printers can lay down variable volumes of ink or have as many nozzles as the pro printers hence the difference in DPI figures but the really important PPI figures will remain constant that being 300 ppi Standard Resolution, 600 ppi Fine Resolution and optionally 1200 Super Resolution on some. Equivalent figures for Epson 360, 720 and 1440

[normhead]

I do agree if you are saying that these technical considerations are just a part of the image making process and need to be put into proper perspective

I'd also say there will be some images that will absolutely use every bit of printer resolution possible, but my expectation would be they are pretty rare, and that the client who would want them would be equally rare.

other than to say that it should not really cost more as the material cost paper and ink will be the same

But based on my experience with my Pixma 1000 Pro, the time taken to print the image increased with the resolution.