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How to size photo to "actual" size?

Doug Larson , Oct 04, 2005; 06:56 a.m.

I'm taking photos of small items (beading and jewelry supplies) for use on my website. I take the pictures of these small items with vaious close up and zoom settings to get the best pictures I can. Because of zooming in or out, I get some larger images and some smaller, but I want to size them to be as close to the "true" size of the item as I can without need for too much of my time spent processing and I prefer to use software that I already own.

I want to let customers view products close to the true size of the items. I use a Nikon 4500, Photoshop elements and a few other things. I can size and scale the photos to print to scale, but can't seem to size them any better for on screen viewing than "hold it up to the monitor" and take a guess at what size the photo needs to be. Is there an easier way to get consistent finished image sizes.

Secondarily, I want to keep things small and efficient as many of my customers still use dial up conections so I need to reduce the file sizes too. The shopping cart I use imposes a 500k upload limit on file size per image.

Thanks for your help, Doug in Texas

A typical image, but it's about double life size.


Walter Burton , Oct 04, 2005; 07:41 a.m.

I'm pretty sure the only thing you can do is add a scale to your images. You know, a little line labeled "1 inch" or something.

People have monitors of all different sizes. I'm typing this on a Sony VAIO VGN-T250P subnotebook. It has a tiny screen with odd dimensions.

William Kahn , Oct 04, 2005; 08:36 a.m.

Walter is right. Besides, at actual size, there wouldn't be enough detail visible on a monitor. What you attached here looks pretty good....

Byron Lawrence , Oct 04, 2005; 09:39 a.m.

get your magnification factors down for your image with whatever lens you are using. whether it is 1:1 or 1:2 etc. then use some calculations on the pixels you have and the print size you need. say you take a picture of a 1" long object and you are focused in at 1:2 sized with a dslr that has a 2056x3088 pixel sensor. this means your projected image on your picture is half sized. so when you print it it will have to be dimensioned twice what the physical size of your sensor is. (say the sensor is about .89x.59 inches. your print will have to be 1.79x1.18 inches... about 1728pixels per inch. for the web (say average monitor resolution is 72ppi) your image needs to be approx. 129x86 pixels. (this math will work without adjustment if you shoot with a canon 10d and a lens capable of close up photos at 1:2 sized... the close limit for many lenses).

You have the nikon 4500 (coolpix i guess). With this, since you don't know the sensor size and the magnification may not be marked on the lens, you will need to measure off a distance (say an 1") that will fit most of your merchandise. take a picture of this at the size you need. in PS make sure your ruler, and grid are showing up. change the PPI setting in image size (no resampling) until you get the image the correct size 1" in the picture = 1" on the ruler (make sure you set your zoom to print size). now go resize your image and check the resample box and change the resolution to 72ppi (dpi in the dialogue box). now when you are back into the main picture, set your zoom to actual pixels. did it change? if so something went wrong. this method is good for web images.

hopefully this helps. actual scaled images are a math of their own. doing CAD with a program is the easy part, plotting the results for say blueprints at 200 scale is the part that many people get tripped up in learning.

as a side note I tend to agree that I don't really want to see jewelery at actual size when I am looking on the web. I can't see the detail. for me the bigger the picture the better.

Frank Kujawski , Oct 04, 2005; 10:31 a.m.

If the monitor is your target, aka web sites, there is not much you can do. Both my wife and I have 19" monitiors. I run mine at 1600x1200 and she runs hers at 1024x768. Her images are almost twice as large as mine. The best you can do is enlarge your image to show detail and put a refernece. A ruler is best, but a dime may work well also, depending on your target audiance. Also graph paper may give a since if scale also.

Doug Larson , Oct 05, 2005; 01:47 a.m.

Thanks for all of your replies. You confirmed my thoughts.... The monitors and other variables make it look different on everyones system. I've started using a scale ruler and I include sizes so that helps.

Thanks Byron, I appreciate the scaling tips, your instructions are a little more detailed that what I was doing so I'll give that a try too and see if that gets me closer to what I was doing.

Does anyone have other resources that give more info on taking close up photos of small items? I'm always trying to learn more but I haven't found much about taking small product photos.

Thanks again, Doug

Joe Shmoe , Jun 13, 2011; 05:37 a.m.

The solution is to add a function to the website, that detects the screen resolution each user visiting your website is using, and then to scale the images depending on these values. Try researching something like "detect screen resolution" on the internet. Here's one example (using a java script):

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