DSF

webtrekker;118299 wrote:If you have an image at, say, 72 dpi, then changing the dpi of the image to 300 will dramatically increase the size of the image, but this is not the right way to do things as the final result will be a blurred or pixellated image. You need an image that has a NATIVE resolution of 300dpi or thereabouts (I wouldn't go less than 200dpi for most things).

This is very informative and obviously took a few minutes to put together, but there is unfortunately a major error at the start: if you change an image's resolution to a greater dpi than original, it will in fact become smaller when printed, not larger. It makes sense as you are effectively crushing the pixels into a smaller area.

The converse is also true - if you decrease the image's dpi its print size increases.

One thing that I used to struggle with is that an image's native size on a screen is ruled by pixel count - ie a 20 x 40 pixel will be a quarter of the size of a 40 x 80 pixel image. The dpi of the image will not affect its size on screen. Print size though is affected by the number of pixels AND the dpi.

As noted above, although it is possible to increase the print size by reducing the resolution, it's rarely satisfactory unless very modest adjustments are made...

Sorry, I was really talking about PPI (pixels per inch), not dpi which, as you rightly say, refers mainly to the printer. For instance, if you have a 100px x 100px image in Photoshop and change the dpi setting for the image from 72 to 300, you will end up with a screen image that is 417px x 417px.

I'd never changed the resolution using photoshop, just reduced image dimensions if necessary and let the resolution look after itself.

Having looked at what Photoshop does, I find it quite surprising that it works as it does - I'm not much above a novice in Photoshop, but since just about everything we produce is printed in one form or another, I can't imagine ever wishing to alter the image size using this method...

Having just played with it further for a couple of minutes, it seems even more bizarre - I opened a (jpg) image at its native resolution of 300ppi, changed it to 50ppi and saved it as a differently named jpg, closed the Photoshop window of original image, then opened the new image, and it was back to 300ppi.

I think that's as good a way as any to confuse myself, so won't be using Photoshop resolution adjustments for the forseeable!

EDIT: Having closed photoshop and then reopened it, on reopening the reduced ppi jpg, it is in fact correctly showing the reduced ppi and consequent reduced image dimensions, so Photoshop was obviously being clever and "remembering" the prior version previously...

Another possibility to throw in to the pot - is the paper secure and not moving/slipping during the pressing process?

Thanks for all the advice so far.

Ok so I've gone through all the advice everyone has given me and there has been massive improvements. The blurry text has now gone and graphics are nice and crisp.

There was / still is an issue with photos. By changing the images to 300dpi the quality of the images when pressing them has increased. However the images do appear dark. I experimented with increasing the brightness on each photo which has helped but I feel that this is only a temporary fix and wish to find out what causes this.

I have found that the size of the initial image supplied by the customer has contributed to my issues. My pile of 'test' mugs has doubled these past few days, it would be interesting to hear how many mugs other people have wasted.

What minimum size (KB/mb) do you guys recommend for sublimating photos?

I was initially supplied photos of 25-30kb and then tried converting these to 300dpi which I think caused a lot of my issues around blurry photos. I spoke with my customer (my wife) about this and when. They supplied the same photos but at 1.5mb the photo quality improved dramatically.

If you were to be printing a "full wrap" image onto a mug, then allowing for a generous space either side of the handle, and with a few mm of bleed top and bottom, then the image size to print onto the sublimation paper would be something like 210mm x 96mm.

if you then convert that to imperial, it's around 8.25" x 3.75".

so, for 300dpi, your image (not from your client, but after you've cropped it, and ready to print) will be:-

(8.25" x 300) = 2,475 pixels

(3.75" x 300) = 1012 pixels.

So, total pixel count will be (2,475 x 1,012) = 2,504,700

Approximately 2.5MP

This doesn't equate nicely to filesizes, due to the variance of images and the differences between filetypes.

300dpi isn't set in stone, small changes in dpi are often not noticeable to the eye...

To be honest, I gave up using photos sent to me by customers for personalisation.

I used to make clocks, and the images they sent were rubbish, meaning I had to spend too much of my time emailing back and forward and altering their photos. To make matters worse, I had to crop a circular section from their photo for many of my clock designs and people were sending me photos that had already been tightly cropped to rectangles. It's just not worth the hassle in my opinion.

If you have your own site where they can upload a photo to the dimensions you state and it's displayed on the product to show them what they'll get, then that's ok, it's putting the ball in their court.

I prefer now to stay away from customers photos and just sell my own artwork with personalised text only, which they can take or leave.

A lot of our work historically has been corporate, which usually involve vector images, solving that issue. Now we have a small public facing shop, where we can discuss face to face with customers all these issues.

Some come in with old, blurry and faded photos that they wish to have on a range of items, we explain that we can scan the photos, but that the end result on their item isn't going to be any better that the original photo.

Since this is all upfront we've had no issues on that front.

I know that it is way too easy to tie up hours playing around with customer's imagery - I often look at the time I spend and shake my head, but I suppose that whilst there are enough hours in the day a sale is a sale...

I am beginning to realise the difficulty in being supplied an image of high enough quality to use. I only supply items to friends so it's not too bad though. They usually supply images via email but I may have to think of a different method for this.

I like the sound of your personalised work webtrekker, do you have a website of the products you sell? It's interesting to see the various products people supply and sell.

I totally understand what your saying wild. I have spent so many hours sorting out just 10 mugs and the price I charge (mates rates) just about covers the cost of the mug let alone my time etc. This is a hobby for me but I am realising now that with my lack of technical knowledge it would be difficult for me to make any money from this.