The price of photo rights ranges from $1 to $100, depending on the size of the image.

Buying a smaller photo can therefore represent serious savings. But buying too small a format can compromise the quality of your presentation. How can you find a happy medium between the two?

Let’s compare these six photos, which range in price from about $20 for the largest to $1 for the smallest. The largest is 16Mb and 4816 x 3621 pixels; the smallest is 175 Kb and 400 x 300 pixels. Here they are shown against letter-size slide in landscape format. (On iStock, these sizes are called XXL, XL, L, M, S and XS)

Regardless of the original size of the photo, you’ll have to enlarge the image to full page to maximize its visual impact. As you can imagine, the smaller photos will become grainy. The question is, at what point can the eye see the pixels? Or, in other words, what is the minimum size you can buy and still get the quality needed for the slide to have impact?

We will consider three cases, depending on whether or not you need to crop the photo for the purpose of your presentation.

Case 1: No cropping, on-screen display

In this scenario, the presentation is viewed on the screen of a computer or an iPad.
We will therefore enlarge each of the photos to the size of a slide. For the purposes of this article, we will only show the face detail in the white rectangle, in actual size.
Here is exactly what your customers will see on your iPad or computer screen, depending on the size of the original image used.

	4816 × 3621 px to 2557 x 1922 px (XXL, XL, L):The quality is perfect, with little or no perceptible difference compared to maximum quality.
	1599 × 1201 px (M) :This is the minimum size that should be used in this scenario. The loss of quality compared to the optimal level is negligible, and the quality is sufficient, although the features are beginning to lose their delicacy
	800 × 600 px: (S)The image is beginning to blur and lose impact.
	400 × 300 px (XS):The image is blurred and has lost all its impact.

Conclusion: for display on a computer screen, 2557 x 1922 px (L) is ideal, and you could go down to 1599 × 1201 px (M), but no smaller.

Case 2: cropping on the computer screen

or image projected onto a 90 cm (36 in) screen

In this scenario, the image is either cropped when presented on a computer or iPad screen, or the slideshow is projected onto a small, 90 cm (36 in) projection screen.

Here is exactly what your customers will see, depending on the size of the original image.

For the purposes of this article, we will only look at the eye in the white rectangle, at the actual size that the customers would see.

	4816 × 3621 Px (XXL) et 3955 x 2973 px (XL):The quality is perfect, with little or no perceptible difference compared to maximum quality.
	2557 x 1922 px (L) :This is the minimum size that should be used in this scenario. The loss of quality compared to the optimal level is negligible, and the quality is sufficient, although the features are beginning to lose their delicacy.
	1599 × 1201 px (M):The image is beginning to blur and lose impact.
	800 × 600 px (S):The image is blurred and has lost all its impact. XS would be even grainier.

Case 3: Major cropping on the computer screen

OR moderate cropping with projection onto a small, 90 cm (36 in) screen or original image projected onto a large screen (3 m or 10 ft)

For this article we are only going to show the detail of the person’s eye as the customers will see it.

	4816 × 3621 Px (XXL):The quality is perfect.
	3955 x 2973 px (XL) :This is the minimum size that should be used in this scenario. The loss of quality compared to the optimal level is negligible, and the quality is sufficient, although the features are beginning to lose their delicacy.
	2557 x 1922 px (L) :The image is beginning to blur and lose impact.
	1599 × 1201 px (M):The image is blurred and has lost all its impact.

For serious zooms or projection onto a large screen, I recommend that you not go lower than 3955 x 2973 px (XL)

Conclusion

For sales presentations, the basic rules of design, including the PSE (Picture Superiority Effect), require that most of your photos be used full screen; however, you will usually be projecting your presentations onto a screen without knowing its size ahead of time… I therefore recommend that you buy images that are at least 2557 x 1922 px (L).

See this news in French: http://presentations-de-vente.com/comment-choisir-la-taille-des-photos-vous-achetez

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