Im a freelancer and to show my work i have a lot of pages which contain just 3 to 5 images about my projects. Most of these pages contain no text at all. I also have pages on my website about my services. They contain a lot of content and in my eyes, they are seo-optimized.
Is it possible that these low quality portfolio-pages hurt/ affect the visiblity of all my webpages, also the services pages, because Google considers a lot of my pages as "low quality"?
Google has an algorithm they call "Panda" that specifically tries to punish sites that have lots of low quality pages. When the algorithm targets your site, all your pages get penalized, not just your low quality ones. For more about it see https://yoast.com/google-panda-low-quality-pages/
Google's biggest problem with low quality pages is when those pages are keyword optimized. They end up ranking and users don't find them useful. There is much less risk when the pages are not designed to rank for anything. Your portfolio pages are unlikely to rank well for anything if you title them "Peesen87's portfolio #1", "Peesen87's portfolio #2", etc. If you give them keyword rich titles they are much more likely to cause you problems.
To be safe you can always "noindex" the pages or disallow them in robots.txt.
Is it possible that these low quality portfolio-pages hurt/ affect the visiblity of all my webpages, also the services pages, because Google considers a lot of my pages as "low quality"?
Yes, there is a risk of getting punishment for the contradiction of Webmaster Guidelines:
Creating pages with little or no original content
I recommend that you base your work on the content on the Search Quality Raters Guideline of Google:
Here are the most important factors to consider when selecting an overall Page Quality rating: ● The Purpose of the Page ● Expertise, Authoritativeness, Trustworthiness: This is an important quality characteristic. Use your research on the additional factors below to inform your rating. ● Main Content Quality and Amount: The rating should be based on the landing page of the task URL. ● Website Information/information about who is responsible for the Main Content: Find information about the website as well as the creator of the Main Content. ●Website Reputation/reputation about who is responsible for the main content: Links to help with reputation research will be provided.
What makes a High quality page? A High quality page should have a beneficial purpose and achieve that purpose well. In addition, High quality pages have the following characteristics: ● High level of Expertise, Authoritativeness, and Trustworthiness (E-A-T). ● A satisfying amount of high quality Main Content, including a descriptive or helpful title. ● Satisfying website information and/or information about who is responsible for the website. If the page is primarily for shopping or includes financial transactions, then it should have satisfying customer service information. ● Positive website reputation for a website that is responsible for the Main Content on the page. Positive reputation of the creator of the main content, if different from that of the website.
And also on the More guidance on building high-quality sites of the Official Google Webmaster Central Blog:
if you want to step into Google's mindset, the questions below provide some guidance on how we've been looking at the issue: Would you trust the information presented in this article? Is this article written by an expert or enthusiast who knows the topic well, or is it more shallow in nature? Does the site have duplicate, overlapping, or redundant articles on the same or similar topics with slightly different keyword variations? Would you be comfortable giving your credit card information to this site? Does this article have spelling, stylistic, or factual errors? Are the topics driven by genuine interests of readers of the site, or does the site generate content by attempting to guess what might rank well in search engines? Does the article provide original content or information, original reporting, original research, or original analysis? Does the page provide substantial value when compared to other pages in search results? How much quality control is done on content? Does the article describe both sides of a story? Is the site a recognized authority on its topic? Is the content mass-produced by or outsourced to a large number of creators, or spread across a large network of sites, so that individual pages or sites don’t get as much attention or care? Was the article edited well, or does it appear sloppy or hastily produced? For a health related query, would you trust information from this site? Would you recognize this site as an authoritative source when mentioned by name? Does this article provide a complete or comprehensive description of the topic? Does this article contain insightful analysis or interesting information that is beyond obvious? Is this the sort of page you’d want to bookmark, share with a friend, or recommend? Does this article have an excessive amount of ads that distract from or interfere with the main content? Would you expect to see this article in a printed magazine, encyclopedia or book? Are the articles short, unsubstantial, or otherwise lacking in helpful specifics? Are the pages produced with great care and attention to detail vs. less attention to detail? Would users complain when they see pages from this site?
I would recommend to place all your works on the one single page, /portfolio/. This page could be so long just as you wish - there is no any malus by the length.
Give each of your works a title and markup it with H3, than place images, which could link to original works.
Google will love, respect and trust you much more, if you save its crawling and indexing resources / calculation capacities. It loves much more a page with many info / info blocks, rather many pages with just a few info.
