Help converting TIFF to high res Jpeg please.

[Sassie]

I need some help. Just installed this software and need help with a specific task. To be totally honest, I don't understand all this algorithm stuff and so would appreciate a very simplified explanation. Here's what I want to do.

I have a 28MB Tiff image (from a 14.6MB RAW image) which I need to convert to a jpg which is between 3MB and 5MB without losing quality. (I am required to submit my image at this resolution)

With my regular settings in Lightroom and CS6 I am only achieving a 1.05MB jpg - too small. (I had cropped the original image - hence the small size).

So, is there a way Mogrify can do this for me? What settings should I select? What algorithm in the drop down list?

Many thanks in advance!

[glennrp]

The setting that most affects JPEG compression is "-quality". Start with "-quality 92" and then increase the value if the filesize is too small or decrease it if the filesize is too large. You probably won't be able to perceive a visual difference between values ranging from 92 to 100, though, although the filesize might increase substantially.

[Sassie]

Hi Glen,

Is that under the 'Total No of Pixels' drop down list? If so, are we talking P, K pixels or Mega pixels?

And which algorithm is a good choice in that drop down list?

[Bonzo]

Drop down list? What software are you using?

[fmw42]

What algorithm in the drop down list?

We are not lightroom experts. The mogify in lightroom calls IM mogrify, but lightroom has its own interface. All we can tell you is what arguments in IM to use in command line mogrify and Glenn has done that. We do not know how lightroom calls those arguments. You need to check with the lightroom organization or forum.

[glennrp]

Hi Glen,

Is that under the 'Total No of Pixels' drop down list? If so, are we talking P, K pixels or Mega pixels?

And which algorithm is a good choice in that drop down list?

The string "Total No" does not
seem to appear anywhere in the ImageMagick source or binary executable files. So, I don't know.

[Sassie]

Oh dear, I didn't understand any of that! Basically I have installed Mogrify as a Lightroom plugin in order to have more control over exporting images at different file sizes, etc. this was following a google search to try and find an answer to the issue I posted about and I found something which recommended this as a Lightroom plugin for giving greater options when saving images at different sizes and formats. I had no idea it was so complicated. There is a drop down list which has resizing algorithm such as quadratic, cubic, Mitchell, Welsh, Lanczos, Sinc, Parzon, etc. I don't know what all that means. Don't even understand what an algorithm is!

[Bonzo]

I did not know you could install mogrify into Lightroom. I use it from the command line or API ( as do probably most of the Imagemagick users ) and so do not have any drop downs and that is what confused me.

The resizing algorithm you mention is a filter and has different effect on different images - one image may look better with one filter whereas another image may look worse. So you would need to try different filters to see which is best on your image.

"Is that under the 'Total No of Pixels' drop down list? If so, are we talking P, K pixels or Mega pixels?" The quality glennrp spoke about is the amount of compression used when compressing the jpg. As you probably know jpg images are compressed when saved. So it is not related to any pixels.

Looking at the plugin instructions it says:
"Compressing JPEGs to a target file size
This option is intended for creating the highest quality JPEG possible that'll be no larger than the requested file size (metadata included). You may find this useful for websites that limit the maximum file size that you can upload.:

This is where you can set your file size so you want to put something between 3000 and 5000 in the box.