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Karen Thompson
09-11-2009, 11:58 AM
Hi everyone, I hope I find you all well.

I wondered if anyone could have a look at the attached photos for me (hopefully I attached them OK) and tell me where I might be going wrong? I’m currently tearing my hair out with this one (and if I’m honest "anything" photo related).

The images were engraved on laser grade ply. My process was to use the original jpg file (was given a scanned copy of the image to begin with but was really awful quality).

Opened the file in Corel Photo-Paint cropped it - resampled it – removed background – vignette – saved.

Then: Imported it in to Photograv did the do with that (chose birch settings) saved etc etc…..

Then: Imported it into the laser's software (Lasercut 5.1).

The 1st image was saved/cut at 5"x3.5" and done using 400 speed and 17 power but needed 2 passes. So I’m thinking it looks OK but would probably look even better if it were bigger. Did “all” the above again but resampled it to a bigger size 7"x5". Used exactly same speed and power but it looks completely different (2nd image). Was I hoping for too much with this??

Sorry for the long post but I feel like banging the head against the wall – I recently seem to be having problems with photos full stop – it’s giving me a crisis of confidence at the moment........ :(

Any suggestions anyone – I have checked all the mirrors/lens etc and all are aligned and clean.

Thanks to all

Karen

PS - just decided maybe I should give it up (for today anyway) and enjoy that rare thing here in Ireland call the sun - it's blistering:)

Dan Hintz
09-11-2009, 12:13 PM
Was the second resize before or after PhotoGrav? It needs to be before...

Also, what resampling method are you using? If you're increasing in size, go with something like a bilinear/cubic and use a sharpening tool after to get back your edges.

Karen Thompson
09-11-2009, 12:27 PM
Hi Dan - Thanks for looking - I really hope I didn't sound like a complete eejit (I'm not normally - well most of the time I'm not:D)


Was the second resize before or after PhotoGrav? It needs to be before...

Resizing for both was done "before" Photograv.



Also, what resampling method are you using? If you're increasing in size, go with something like a bilinear/cubic and use a sharpening tool after to get back your edges.

All I'm doing in Corel Photo-Paint (X4) is Cropping the image first then going to Image-Resample then I put in the size I want and change the DPI (I used 600 on both these images) I haven't been changing any other settings. Then I've just been saving it and going to the next stage.

Karen

Dave Lock
09-11-2009, 3:38 PM
Hi Karen,

What setting did you make your scan gap? For a 600 dpi image the scan gap should be set to 0.042

I have found on our Chinese machines that using 300 dpi image can produce a better result, particularly on plywood.
If you give it a go with a 300 dpi image don't forget to change your scan gap to 0.085

I'd be interested in seeing your results.

Regards

Dave.

Karen Thompson
09-11-2009, 4:50 PM
Hi Karen,

What setting did you make your scan gap? For a 600 dpi image the scan gap should be set to 0.042

I have found on our Chinese machines that using 300 dpi image can produce a better result, particularly on plywood.
If you give it a go with a 300 dpi image don't forget to change your scan gap to 0.085

I'd be interested in seeing your results.

Regards

Dave.

Hi Dave
Thanks for that - I gave up earlier as it was "doing my 'ead in" and I wanted to make the most of this fantastic weather we're having at the moment ;). Well overdue!!!!

Anyway - I digress - I think the scan gap was at 0.07 - but I'll try the 300 dpi and see how that goes. I wasn't given any scan gap settings with the machine and didn't see any on the DVD's supplied apart from the materials they demo'd with. So it really has been trial and error......

I'll let you know how it goes. Thanks again Dave.

Karen :)

Dave Lock
09-11-2009, 4:59 PM
Karen,

I have attached a file containing a chart which I think you will fine useful.

It basically shows the dpi (imperial) of your image and what the metric conversion is to use for your scan gap.

It's the amount the y-axis will travel after each pass of the x-axis. It's important that this is set to the same as the resolution of your picture.

You can print it out, cut it to size and stick it on your machine control panel.

Hope it helps.

Dave.

Karen Thompson
09-11-2009, 5:03 PM
Dave - Next time I'm in the UK I'll be standing you a pint or two.

Thank you (again):)

Dave Lock
09-11-2009, 5:10 PM
Dave - Next time I'm in the UK I'll be standing you a pint or two.

Thank you (again):)


Just printed that post for future reference :D:D

We are all here to help if we can.

Regards

Dave.

Dave Johnson29
09-11-2009, 5:22 PM
Dave - Next time I'm in the UK I'll be standing you a pint or two.


Karen,

I have not run Dave's spreadsheet, but I wrote a small free program and posted it here some time back. It reads the actual DPI in both Metric and Imperial (I think) from BMP and JPG files.

If the DPI is not stored with the original JPG, Corel will arbitrarily puts 72 in there. That used to be the old scanning standard for B&W. Not sure why they still do it.

I'll see if I can find that program here and post the link.

Here is the post with a link to my website
http://www.sawmillcreek.org/showpost.php?p=1028285&postcount=1

Ooops, only Imperial, I will make a quick change and replace the copy at that link on my website.

Karen Thompson
09-11-2009, 5:28 PM
I think you can "officially" call that a Beer Token :) :)

Karen Thompson
09-11-2009, 5:37 PM
Dave J - thank you too. Blimey I have alot of homework to do tomorrow :)

Pints all round I think...... :)

Cheers... !!!

Dave Johnson29
09-11-2009, 6:53 PM
Pints all round I think...... :)


Hi Karen, I have updated the program for Metric and it is now on my website under Software.

Bear in mind the program only reads what is in the header and nothing else. The idea of it is to be able to read the DPI etc before loading it into Corel.
If there is no DPI in the header then Corel will incorrectly, in most cases, show 72dpi and save it back out as that.

Make mine a pint of Theakston's Old Peculiar. Yum :D Theakston's is like peanuts, you can't just have one.

Karen Thompson
09-12-2009, 5:44 AM
Make mine a pint of Theakston's Old Peculiar. Yum :D Theakston's is like peanuts, you can't just have one.

Old Peculiar.......... wow haven't heard of that one in a long time, but no problem I'll remember that just for you :D:D

Thank you all once again - about to go and have a play now.
Have a god weekend everyone!!!

Karen

James Jaragosky
09-13-2009, 7:41 PM
Hi Karen,

What setting did you make your scan gap? For a 600 dpi image the scan gap should be set to 0.042

I have found on our Chinese machines that using 300 dpi image can produce a better result, particularly on plywood.
If you give it a go with a 300 dpi image don't forget to change your scan gap to 0.085

I'd be interested in seeing your results.

Regards

Dave.

DPI and scan gap question.
I was under the assumption that printing a 300 dpi photo using a 300 dpi ink jet printer; that the printer sprays out tiny dots of ink that are .005 in diameter to form the picture. So if a 300 dpi image is made up of .005 dots******* ///why would you use a scan gap of .085 with a 300 dpi image? Would not a scan gap of .005 work best? That would place the dots exactly next to each other.
I know that my logic is somehow flawed because I currently use a scan gap of .05 and I get acceptable results. ( I will run a test later with a .085 scan gap)
I also was under the assumption that my laser produced a .005 diameter dot at its optimum focal point, this information I obtained from my users specifications.
So am I wrong about the size of the beam dot? What the heck am I missing?

Dave Lock
09-13-2009, 9:13 PM
Hi James,

Mentioned earlier in the thread the scan gap is a metric value, it's the metric equivalent to the imperial dpi. You might say its .085mm per inch is the same as 300 dpi.

Regarding the dot size. If the dot measured .005", 300 dots placed exactly next to each other would give you 1.5" so to place them at the side of each other over 1 inch they would overlap by 30%.

If you are currently using .05 as your scan gap that's the same as around 508 dpi. In this case a .005" dot size overlap would be considerable. I have found that so much overlap causes a loss of clarity in the output hence I mainly use images no larger than 300 dpi.


Like most people, when talking about images I think in terms dpi. I find it difficult to work in dots per mm or Cm or whatever it is. Thats why I use the conversion chart. A quick glance at the chart tells me what the scan gap should be for a given dpi.

Sorry if that's about as clear as mud!!

Regards

Dave.

James Jaragosky
09-13-2009, 9:43 PM
Hi James,

Mentioned earlier in the thread the scan gap is a metric value, it's the metric equivalent to the imperial dpi. You might say its .085mm per inch is the same as 300 dpi.

Regarding the dot size. If the dot measured .005", 300 dots placed exactly next to each other would give you 1.5" so to place them at the side of each other over 1 inch they would overlap by 30%.

If you are currently using .05 as your scan gap that's the same as around 508 dpi. In this case a .005" dot size overlap would be considerable. I have found that so much overlap causes a loss of clarity in the output hence I mainly use images no larger than 300 dpi.


Like most people, when talking about images I think in terms dpi. I find it difficult to work in dots per mm or Cm or whatever it is. Thats why I use the conversion chart. A quick glance at the chart tells me what the scan gap should be for a given dpi.

Sorry if that's about as clear as mud!!

Regards

Dave.
Thanks for clearing that up for me. your explanation was very clear.
Jim J

Karen Thompson
09-14-2009, 10:48 AM
Good Afternoon All

Well, I just thought I’d let you know how I got on. I had a play about with this photo (again) and with the scan gap settings according to the suggestion made by Dave Lock (thanks again Dave).

Now I have come to the conclusion that either I’m totally useless or it’s just this particular photo :D.

What I have found that if I keep the photo to its original size (or smaller) it’s fine – however it’s when I enlarge it that the problem comes up. I’ve attached photos of the results done at 300 dpi, apologies for the quality (note: all size resampling was done from the original image before photograv etc...).

As you can see (hopefully) the guys face in the smaller version has more clarity to it than the larger one – this is what’s making me wonder about increase in size causing the problem. I know I have much to learn about photo-paint amongst other things :rolleyes:.

Anyway thankfully the guy isn’t in a rush for the piece so I will have to tinker about a bit more I think.

Comments/critisms (sp). are all very very welcome:D:D
Thanks everyone for your input so far.

Regards
Karen

Darren Null
09-14-2009, 11:09 AM
Just a resize shouldn't be doing that. What software are you using? Is the original image big enough? Can you post the original graphic? Are you doing anything else while resizing?

Dan Hintz
09-14-2009, 11:21 AM
Karen,

Both times you've posted these images the differences always look like contrast changes. In this sequence, the first one looks too light for the woman, and the second is too dark for the guy. I have to ask the same as Darren... are you certain nothing else is being done to these images? No other filters have been chosen for post-processing (either graphics software or laser driver)?

Karen Thompson
09-14-2009, 11:39 AM
Just a resize shouldn't be doing that. What software are you using? Is the original image big enough? Can you post the original graphic? Are you doing anything else while resizing?

Hi Darren

Original pic attached - I'm using Corel Photo-Paint (X4).

Firstly, I'm cropping the image to cut out most of the background then Image-Resample then selecting the size I want say 20cm width and dpi (originally) at 600; after that I've then gone to Image-Cutout Lab to take out the background then the vignette - That's It!!

The above was the same when I tried the photo at 300 dpi and each one was done from the original image (attached).

I'm ready to give up at this point:rolleyes: - but I'm also "pigged off" enough to not let it beat me:D.

Karen

Karen Thompson
09-14-2009, 11:47 AM
Karen,

Both times you've posted these images the differences always look like contrast changes. In this sequence, the first one looks too light for the woman, and the second is too dark for the guy. I have to ask the same as Darren... are you certain nothing else is being done to these images? No other filters have been chosen for post-processing (either graphics software or laser driver)?

Hi Dan,
I'm positive no other filters are being used in photo-paint and as for LaserCut, I haven't touched the driver software.

I'm now at a complete loss this is the 1st photo I've had any problems with..........so far:rolleyes: .

Regards
Karen

Darren Null
09-14-2009, 12:32 PM
20cm width and dpi (originally) at 600
Well there's a lot of your problem right there. If that's the original image, you're left with about 888 x 616 pixels of useable image after cropping the background.

So 20cm @ 600dpi....that's.....(wanders around muttering)...2 362.20473 pixels across needed; so your program is interpolating -making up- the extra pixels. You're asking paint to make the image 265% larger and -frankly- it's not happy with that. Anything above a 50% upsample, and you should really go with a program designed specifically for that.

I use this one, because it's free and works as well as anything, and better than most:
http://sourceforge.net/projects/imageenlarger/

So. Enlarged it (2500px across- gives you some wiggle room). Played around with the settings. Cropped out the background. Saved as a .png to keep the invisible background.

EDIT: 20cm@600dpi is !!!4725px!!! across. It was the conversion from imperial that got me. *facepalm* Update coming....

Karen Thompson
09-14-2009, 1:18 PM
Haha that all makes sense now...... Darren I've sent you a PM and a HUGE thanks.

I'll start again......... we'll see how it goes:D:D.

More than likely I'll be back again:eek::eek:.

Karen

Darren Null
09-14-2009, 3:36 PM
Here you go:
http://ropa-militar.com/aaa_e0.zip

It's a 79Mb tif file compressed to a 26Mb zip. No chance whatsoever of getting it on the board, hence the direct link. And while I was in there I knocked a bit off the chap's suntan so the features ought to come out more evenly.

The original was a 532% increase...no wonder the big image looked sheddy. That's pushing it even with enlargifying software.

MR.MATTHEW ROUSE
10-14-2009, 10:15 AM
Hello,

when you talk about gap setting.is that on the laser software itself or in corel or in some other software?
This is somehting totally new to me so forgive my dumb question if it is one.
Thank you in advance

James Jaragosky
10-14-2009, 11:45 AM
Hello,

when you talk about gap setting.is that on the laser software itself or in corel or in some other software?
This is somehting totally new to me so forgive my dumb question if it is one.
Thank you in advance
I set my scan gap with the laser software. In Newelydraw it is under the raster properties settings.

Barb Macdonald
10-14-2009, 6:36 PM
I like the first one, and lower dpi is usually better, and no, you are not an eedjit.
I wear that particular crown.
Crappy photo=Crappy Image.
But I like the first one!
It's great! Don't be so perfectionistic, if you can. Not everybody has your eye. It's a photo:)
Looks good to me:)
(cowers)