Difference between LED and LASER imaging

umesh

Member
Hi,
This is regarding the Imaging process in digital presses.

I am bit confused about the resolution part, I know that imaging can be done by either LED or LASER, so when we say 600X600 or 1200 X 1200 its done by LED and bit depth is adjusted to achieve req. gray levels.
In case of LASER, resolution is like 2400 dpi and bit depth cannot be varied.

What I want to know is that, whether quality from LASER imaging system will always be better than LED ?

What will be the difference in Dot quality, speed, and cost of the equipment, also will there be a difference in maintenance part ?

and one more.. In digital, Is the screening pattern, dot shape, size and screen angles similar to that of offset ?


Regards,
Umesh
 

Craig

Well-known member
Good question, now let's see if the answers are biased by manufacture. Get ready to read between the lines!
 

sweatyclimber

Well-known member
So here's my 8(bit) sense... sorry lame pun :p

I have seen both work great and be saleable. Check 1. No "one" technology matters most towards image quality... IE: inkjet can be 9600DPI... is it better then laser/ LED ...NO not usually.

Without getting too technical here's one way to look at it. Your image be it LED or Laser is a mosaic. With LED you have bigger tiles but more choices, with Laser you have smaller tiles but have to assemble those to create the color's your eye see's. In the case of both of these mosaics, your looking at it from a skyscraper (to street) point of view. Now factor into that is the mosaic made of corogated cardboard or bathroom tile (affects of paper), are the tiles torn or symetricly created (toner).

So the quick answer is, look at the output against your jobs and see what is more saleable. The 8-bit verse 2400dpi conversation is a marketing talk. Here's the gist of the two and as craig said "between the lines" you can see it just depends:

1. (8-bit) I have an 8-bit LED device which makes me capible of creating 16million colors... Since I can physically recreate them, I have a better color gamut and choice..... an objection response: I don't need 2400dpi because I print the right color on the pixal the first time.

2. (High DPI) I have system that is 2400DPI, therefore when layering the colors you will see (or your eye will percieve) more color options, and an image that is crisper, more vibrant and accurate.... an objection response: I control the color down to the minute area and therefore give you the most accurate reproduction possible... Film created the best pictures because of it being millions of DPI, Your HD TV also increases resolution because resolution is what makes a great image!

Don't be fooled by marketing messages... Are they valid points yes but its still color, so its still subjective and clearly neither are difinitavely a better way to look at color. What I will tell you is that KM who was the first with LED color, changed to laser for there production gear... That is at least a little telling...

--Not mentioned is how they both "split the pixel" to get better "fine lines" both use interpolation. One just makes it the main talking point because the other can only interpolate well on b/w.
 

kire

Member
So here's my 8(bit) sense... sorry lame pun :p

I have seen both work great and be saleable. Check 1. No "one" technology matters most towards image quality... IE: inkjet can be 9600DPI... is it better then laser/ LED ...NO not usually.

Without getting too technical here's one way to look at it. Your image be it LED or Laser is a mosaic. With LED you have bigger tiles but more choices, with Laser you have smaller tiles but have to assemble those to create the color's your eye see's. In the case of both of these mosaics, your looking at it from a skyscraper (to street) point of view. Now factor into that is the mosaic made of corogated cardboard or bathroom tile (affects of paper), are the tiles torn or symetricly created (toner).

So the quick answer is, look at the output against your jobs and see what is more saleable. The 8-bit verse 2400dpi conversation is a marketing talk. Here's the gist of the two and as craig said "between the lines" you can see it just depends:

1. (8-bit) I have an 8-bit LED device which makes me capible of creating 16million colors... Since I can physically recreate them, I have a better color gamut and choice..... an objection response: I don't need 2400dpi because I print the right color on the pixal the first time.

2. (High DPI) I have system that is 2400DPI, therefore when layering the colors you will see (or your eye will percieve) more color options, and an image that is crisper, more vibrant and accurate.... an objection response: I control the color down to the minute area and therefore give you the most accurate reproduction possible... Film created the best pictures because of it being millions of DPI, Your HD TV also increases resolution because resolution is what makes a great image!

Don't be fooled by marketing messages... Are they valid points yes but its still color, so its still subjective and clearly neither are difinitavely a better way to look at color. What I will tell you is that KM who was the first with LED color, changed to laser for there production gear... That is at least a little telling...

--Not mentioned is how they both "split the pixel" to get better "fine lines" both use interpolation. One just makes it the main talking point because the other can only interpolate well on b/w.
Great answer!! Bits and bytes is always marketing stuff, look behind it and find out what the facts(results) are. And laser or LED is only the half of what quality you can expect. My advise is always to also take a closer look at the controllers/RIP´s because you will need a lot of power if you want to process all "large" files the salesrep says is no problemas..... and then you have screening, dots etc etc etc.
 

umesh

Member
Thanks for your the excellent information Climber,
I think whatever you are saying really makes sense, but as you said dots made from LASER are sharp, and crisp I think images produced BY laser looks far better.
Actually I came to this conclusion after seeing outputs from KM's LED and LASER products.Prints from their production series looks far superior than that of their lower range which uses LED.

But any ways I agree that just the source of imaging cannot totally decide on the quality of prints.

Secondly, can any one put some light on the shape and size of dots in digital printing, is it similar to that of offset ?

Thanks
 

michaelejahn

Well-known member
Spots, dots ...

Spots, dots ...

Secondly, can any one put some light on the shape and size of dots in digital printing, is it similar to that of offset ?

Thanks
um - which 'type' of digital printing ?

There are significant marking engine differences (the gadget that impinges some toner, pigment or ink) between something kike the Xerox iGen4 and the HP Indigo W7200 Digital Press.

While I am temped to ask "why would this really matter to you" ...I will assume the answer might as well be "just because I want to know if that metters...

I would suggest that things like warm up ties and 'how fast, how consistant and MTBF issues would be much more important metrics to compare than imaging approaches.

Anyway...in some systems, the way the substrate is imaged requires heat and fusing, so the "dots" might be a 'spots' that are melted in place while in another system, spots picoliter sized droplets might be aggregated into what might be a dot, or might be a dithered pattern.

So, for example, I could show photomicrographs of different systems, and depending on what I am showing, one might look "better" in the photomicrograhp than another, but that nds up meaning very little in the larger scheme of things.

Here are a few examples.

Printing & Imaging Expertise Center - HP vs Xerox Worry-free printing - HP Small and Medium Business

Printing & Imaging Expertise Center - HP vs Xerox Print quality & performance - HP Small and Medium Business

but, one might argue "so, how much intervention is required to keep the beast running ?

Chevalier first to install the new iGen4 by Xerox - Chevalier International
 

Kingsfish

Member
at the end of the day...

at the end of the day...

it is all about what comes off the end of the finisher...havent seen the perfect machine for everything yet, so:

1. choose (spend some time on) different files that will test the abilities of the engines you are looking at. solids/highlights/midtones/registration/color density shifts on the sheet...

2. take different papers to the vendors and run the machine to your hearts desire...if they believe that you are testing the machine and not running free work, then you should have carte blanche

3. hopefully they have someone on the technical side of helping you setup/configure driver settings to tweak diff jobs asking for different things
 

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