Going exclusive is probably one of the biggest (and hardest) decisions that a microstock  photographer has to make. Most choose to remain non-exclusive, but for some the lure of higher royalty rates and less 'work' uploading to multiple sites is too much to resist.
Exclusive Contributors v Exclusive Photos
There are two main types of exclusivity in microstock:
- Exclusive Photos: an image is only offered for sale on a single site in return for the site taking a lower commission rate if that image is sold. Exclusive images have a cache with buyers who feel, perhaps wrongly that nothing like them can be found elsewhere.
- Exclusive photographers: a contributor who has agreed that they will only market their work via a single site. This usually means that they cannot sell any other RF  images via any other agency. Contracts usually allow them to sell other photography work for example portraits, event photos, or rights managed  work via a different outlet.
So, is it worth selling some of your images at only one agency? There are a couple of things to consider when making the decision. Firstly there is the increase in royalty income on each sale. If you create exclusive photo then you need to recoup the cost of creating that work from just one agency, with the cost in creation being a large factor in microstock due to the relatively low incomes for the majority of images then, for me, I would argue it's better to spread the burden across several agencies in a bid to earn more. If an exclusive image only generates a 10% higher royalty then you had better hope that in being 'exclusive' that image can generate a significantly higher number of downloads than if would if it were non-exclusive.
Here lies the problem with making a decision, most agencies with exclusive options weigh their search results or the layout of their site to benefit exclusive images or increase sales of exclusives by offering them in a more prominent place. Exclusive images are also offered in premium collections. This is done to benefit buyers and the photographers who choose to go exclusive but it makes it almost impossible to accurately calculate any benefit from uploading exclusive photos.
Agencies Selling Exclusive Photos:
(while still allowing photographers to upload different photos to other agencies)
- Fotolia:  'Partially Exclusive Photos' can be set to cost more to end users, hence earning a higher income per sale, but only if you are bronze ranking or above. If you have only just started selling with Fotolia then there is little advantage in their current payment plan. It looks like emerald contributors get similar options (but we are talking serious sales to reach emerald rank)
- Dreamstime:  Bonus 3-5% depending on the number of times an image has sold (reduced from 10% in Aug 2009), photographers report that sales are noticeably higher on their exclusive photos.
- Panthermedia:  not an exclusive option as such, but an increase of 20% on royalty (up to 50%) on photos that are 'not sold at a lower price elsewhere'. Featurepics  also offer a similar bonus for their 'midstock  images'.
Also known as 'Total exclusivity'. A big part of the decision here is related to your current business model / style of photography. Going exclusive with an agency should reward you with increased hits in search results or access to premium collections etc. Another potential bonus is that you only have to upload and categorize at one agency, I'd argue that with the right workflow you can upload to multiple agencies with little extra fuss, the main work in microstock is taking the pictures and keywording them. Hence look at improving your workflow if you feel that 'time saving' is a main factor in your choice.
Microstock Agencies offering Exclusive contracts:
- istockphoto:  Exclusive photographers on istock get an instant jump up from 28% to 35% per image sale, contributors at higher canister levels earn up to 50% per download. istock exclusives also benefit from a raft of other perks, shorter review times, 10% extended license bonus, business cards, and quote from istock "Exclusivity brings more attention to your portfolio". Exclusive photographers also receive help from istocks legal team if any misuse of their images is discovered. You need to have 250 downloads (bronze canister level) and a 50% acceptance rate to apply.
- Dreamstime:  Exclusive photographers always receive a 60% royalty regardless of the number of sales an image makes, compare with 20-25 for non exclusive. Exclusives also get an extra 20c per accepted upload. You at least need 50 images accepted to apply for exclusivity.
- Fotolia:  Totally Exclusive Contributors have the same options of partial exclusive photos i.e. they can increase the price of the photos, they also benefit from earning 17% higher royalty on each sale. Despite being an impressive increase in earnings few photographers seem to have taken Fotolia up on their exclusivity offer, or if they have they are keeping quiet about it. While a 17% increase is impressive the images also need to be selling a lot more frequently to make it worthwhile.
Making the Decision
All your eggs in one basket... it's often said, but it should be less of a concern for most people, it's little different to relying on a full-time employer for an income, excepting that fact that employers have legal requirements and often pay redundancy in the event of 'separation'. Are you comfortable with taking a significant amount of your income from a single place? If it's an established agency like those listed here then I feel there is little to worry about unless you purposefully try to 'rock the boat' or do something that contravenes your contract.
I made my decision a long time ago, and after doing the research for this article, I'm convinced it was the right one for me - non exclusivity gives me freedom (decision made before I started this site of course - that would bias my decision). Because of the variables involved, I've come to the conclusion it is hopeless for me to offer direct advice on this topic. All I can do in this article is inform. It's not an easy decision, and comparing potential earnings is difficult, although istock has a tool to estimate the value to going exclusive their raw data on commission rates, I feel is organised to make a comparison between exclusive and non-exclusive difficult by not presenting percentage royalties.
Go with the crowd - There are a lot more non-exclusive microstock photographers than exclusives... can we work out why?
Not everyone is accepted as an exclusive photographer, to be in with a chance at it you have to be shooting good images and have a high acceptance rate.
It's Difficult To Change
One possible reason there are so many non exclusive photographers is the fact that it is so difficult to change between the two. If you have a portfolio with several sites you need to delete all the images in it, and in some cases those images might not be available for some exclusive contracts as they have been previously offered for sale somewhere else or at a lower price. Most microstock wannabes start out contributing to several sites and by the time they get the idea they like microstock it's a bitter pill to take in deleting a portfolio that is earning. In doing so you write-off the time that you spent uploading it. A typical pitfall is the Dreamstime contract which has a minimum term of six months for sale after an image is uploaded - you can't delete more than 70% of the images during that first six period, that of course is not a problem if Dreamstime is who you plan to go exclusive with.
The same applies to moving from exclusive to non-exclusive, for example quitting exclusivity at istockphoto as a diamond photographer will cut income immediately by 50%, true that most small-time contributors are probably not up to that level but they will still face a large cut in earnings with immediate effect. As most contributors know it would take a long time upload their entire collection to several other sites to make up for this loss.