Why does my old HP 6L print images better than my newer HP laserjets?

smeelah

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I have also been confused by the Ginkgo Test image. Copying and printing it from post #6 produces a 20mm x 20mm print, but opening the image in a new tab and copying it produces a 15 cm x 15 cm print, so the image in post #6 is a thumbnail I think.

A 300 dpi scan of the thumbnail print made by the HP Laserjet 1018 looks very similar to the right hand print of post #1:

View attachment 14229
Hi Peter,
I'm wondering if you ever got a good print with the 1018?
thanks!
 

PeterBJ

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I have only had the results I have already posted. If the HP Laserjet produces a good print I will let you decide.

I wondered about the coarse raster produced by the Laserjet 1018 and the old inkjet printer HP Deskjet 930. I printed a test image containing a greyscale with the laser printer. I examined it with a USB microscope at 50 times magnification and compared it to a millimetre paper printed on the Canon MP980. Here is a 5mm x 5mm crop of the millimetre paper print, click to enlarge:

Millimeter blue 5x5.jpg

And here is a 5mm x 5mm crop of a field of the greyscale, click to enlarge:

Millimeter 5x5 HPLJ raster.jpg

Counting the dots you get 15 dots per 5mm or approximately 76 dots per inch??

But maybe resolution in dpi is not the same as counted dots per inch in the printed raster?

Maybe someone who knows more about this subject could explain?
 
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Printguy

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Hi!
I've always used an HP 6L to print small detailed images for my jewellery design business. I've been having new issues with the printer and so I've started trying to find a replacement. Both my HP 1018 and HP MFP M28w print fine except that with images, you can see the dots. The images are not smooth. Increasing the resolution has not helped. I've tested different drivers, different settings, different apps. I'm using Mac OS 10.12 at the moment.

I would appreciate any help or a point in the right direction.
Thanks,
Leila
View attachment 14194

Your HP 6L appears to be printing halftones using the Floyd-Steinberg dithering algorithm (https://en.wikipedia.org/wiki/Floyd–Steinberg_dithering), which is arguably the best one for the job. HP M28w, however, uses a generic dotted halftones pattern. The difference is caused by the printer drivers, actually, not the printers themselves.

It is worth noting that both printers are capable of printing the images identically, if you do the pre-processing yourself in Photoshop by following these steps:

1) Convert the image to grayscale
2) Resample the image to use the target image size and native printer resolution (such as 600 dpi)
3) Convert the image to black-and-white, using the appropriate dithering algorithm
4) Print without scaling, at 100%
 
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smeelah

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Your HP 6L prints halftones using so called Floyd dithering, which is, arguably, the best dithering algorithm. HP M28w, on the other hand uses generic dot-bases halftoning


Your HP 6L appears to be printing halftones using the Floyd-Steinberg dithering algorithm (https://en.wikipedia.org/wiki/Floyd–Steinberg_dithering), which is arguably the best one for the job. HP M28w, however, uses a generic dotted halftones pattern. The difference is causes by the printer drivers, actually, not the printers themselves.

It is worth noting that both printers are capable of printing the images identically, if you do the pre-processing yourself in Photoshop by following these steps:

1) Convert the image to grayscale
2) Resample the image to use the target image size and native printer resolution (such as 600 dpi)
3) Convert the image to black-and-white, using the appropriate dithering algorithm
4) Print without scaling, at 100%
This is amazing information. Thank you. Is it possible to add a dithering algorithm to photoshop or do I need to work the with the options available?
 

Printguy

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This is amazing information. Thank you. Is it possible to add a dithering algorithm to photoshop or do I need to work the with the options available?
Yes, it is possible. "Diffusion Dither" is the Floyd-Steinberg one. There are 3 other built-in methods, or you can create a custom one:

bitmap.png
 
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